JP2020056592A - Radar apparatus - Google Patents

Abstract

To accurately detect an object with a radar apparatus.SOLUTION: A radar receiving unit 200 includes a plurality of transmitting antennas 108 and a radar transmitting unit 100 for transmitting a transmission signal through the plurality of transmitting antennas 108. Disposed positions are the same as to at least two virtual antennas out of a virtual receiving array including a plurality of virtual antennas configured based on a plurality of receiving antennas 202 and the plurality of transmitting antennas 108, and a transmission interval is equal between the transmission signals to be transmitted sequentially from the transmitting antennas 108 corresponding to the at least two virtual antennas out of the plurality of transmitting antennas 108.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a radar device.

  In recent years, a radar device using a radar transmission signal having a short wavelength including a microwave or a millimeter wave capable of obtaining high resolution has been studied. Further, in order to improve outdoor safety, there is a demand for development of a radar device (wide-angle radar device) that detects a small object such as a pedestrian or a falling object in a wide-angle range in addition to a vehicle.

  As a configuration of a radar device having a wide-angle detection range, a reflected wave is received by an array antenna composed of a plurality of antennas (antenna elements), and a reflected wave is obtained by a signal processing algorithm based on a reception phase difference with respect to an element interval (antenna interval). (Direction of Arrival (DOA) estimation) for estimating the angle of arrival (direction of arrival). For example, the angle-of-arrival estimation method includes a Fourier method (FFT (Fast Fourier Transform) method), or Capon method, MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) as methods for obtaining high resolution. ).

  Further, as a radar apparatus, for example, a configuration in which a plurality of antennas (array antennas) are provided on the transmission side in addition to the reception side and beam scanning is performed by signal processing using a transmission / reception array antenna (MIMO (Multiple Input Multiple Output) radar) Has been proposed (for example, see Non-Patent Document 1).

JP 2008-304417 A JP 2011-526371 A

J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas," Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas," Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007M.Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure ", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 Direction-of-arrival estimation using signal subspace modeling Cadzow, J.A .; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page (s): 64-79

  However, a method for detecting a target (or target) in a radar device (for example, a MIMO radar) has not been sufficiently studied.

  One embodiment of the present disclosure provides a radar device that can accurately detect a target.

  A radar device according to an aspect of the present disclosure includes a plurality of transmission antennas, and a transmission circuit that transmits a transmission signal using the plurality of transmission antennas, based on a plurality of reception antennas and the plurality of transmission antennas. In a virtual reception array including a plurality of virtual antennas, the arrangement positions of at least two of the virtual antennas are the same, and among the plurality of transmission antennas, a transmission antenna corresponding to the at least two virtual antennas The transmission intervals of the transmission signals transmitted sequentially are equal intervals.

  Note that these comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, and the system, the apparatus, the method, the integrated circuit, the computer program, and the recording medium May be realized by any combination.

  According to an embodiment of the present disclosure, it is possible to accurately estimate an arrival direction in a radar device.

  Further advantages and advantages of one aspect of the present disclosure will be apparent from the description and drawings. Such advantages and / or advantages are each provided by some embodiments and by the features described in the description and drawings, but not necessarily all to achieve one or more identical features. There is no.

FIG. 1 is a block diagram illustrating a configuration example of a radar device according to an embodiment. FIG. 3 is a diagram illustrating an example of a radar transmission signal according to one embodiment. The figure which shows an example of the transmission switching operation | movement which concerns on one Embodiment. FIG. 4 is a block diagram showing another configuration example of the radar transmission signal generation unit according to one embodiment. FIG. 5 is a diagram illustrating an example of a transmission timing of a radar transmission signal and an example of a measurement range according to an embodiment. FIG. 4 is a diagram illustrating an example of transmission timing according to one embodiment. FIG. 4 is a diagram illustrating an example of transmission timing according to one embodiment. FIG. 4 is a diagram illustrating an example of transmission timing according to one embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on one Embodiment. FIG. 4 is a diagram illustrating an example of reception timing for each virtual antenna according to one embodiment. The figure which shows an example of the transmission antenna arrangement which concerns on one Embodiment The figure which shows an example of the receiving antenna arrangement concerning one Embodiment The figure which shows an example of the virtual reception array arrangement | positioning which concerns on one Embodiment. FIG. 4 is a diagram illustrating an example of reception timing for each virtual antenna according to one embodiment. FIG. 7 is a diagram illustrating an example of transmission timing according to Variation 1 of the embodiment; FIG. 11 is a diagram illustrating another example of the transmission timing according to Variation 1 of the embodiment; FIG. 11 is a diagram illustrating another example of the transmission timing according to Variation 1 of the embodiment; The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 2 of one Embodiment. FIG. 7 is a diagram illustrating an example of transmission timing according to Variation 2 of the embodiment; The figure which shows the other example of the antenna arrangement | positioning which concerns on the variation 2 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 3 of one Embodiment. The figure which shows the other example of the antenna arrangement | positioning which concerns on the variation 3 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the transmission switching operation | movement which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the transmission switching operation | movement which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the transmission switching operation | movement which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the antenna arrangement | positioning which concerns on the variation 4 of one Embodiment. The figure which shows an example of the transmission switching operation | movement which concerns on the variation 4 of one Embodiment. Block diagram showing a configuration example of a radar device according to variation 5 Block diagram showing a configuration example of a radar device according to variation 6 Diagram showing an example of a transmission signal and a reflected wave signal when a chirp pulse is used

  The MIMO radar transmits a signal (radar transmission wave) multiplexed using, for example, time division, frequency division, or code division from a plurality of transmission antennas (or transmission array antennas), and a signal reflected from a surrounding object ( A radar reflected wave is received using a plurality of receiving antennas (or called a receiving array antenna), and a multiplexed transmission signal is separated from each received signal and received. Through such processing, the MIMO radar can extract a complex propagation path response represented by the product of the number of transmission antennas and the number of reception antennas, and performs array signal processing using these received signals as a virtual reception array.

  Further, in the MIMO radar, by appropriately arranging the element intervals in the transmission / reception array antenna, the antenna aperture can be virtually enlarged and the angular resolution can be improved.

  For example, in Patent Document 1, as a multiplex transmission method of a MIMO radar, a MIMO radar using time division multiplex transmission that transmits a signal with a transmission time shifted for each transmission antenna (hereinafter, referred to as a “time division multiplex MIMO radar”). ) Is disclosed. Time division multiplex transmission can be realized with a simpler configuration than frequency multiplex transmission or code multiplex transmission. In time division multiplex transmission, orthogonality between transmission signals can be favorably maintained by sufficiently widening transmission time intervals. The time division multiplexed MIMO radar outputs a transmission pulse, which is an example of a transmission signal, while sequentially switching transmission antennas at a predetermined cycle. The time-division multiplexing MIMO radar receives a signal in which a transmission pulse is reflected from an object by a plurality of reception antennas, and performs a correlation process between the reception signal and the transmission pulse, for example, a spatial FFT process (estimation of arrival direction of a reflected wave). Processing).

  The time division multiplexing MIMO radar sequentially switches a transmission antenna for transmitting a transmission signal (for example, a transmission pulse or a radar transmission wave) at a predetermined cycle. Therefore, time-division multiplexing may require a longer time to complete transmission of transmission signals from all transmission antennas than frequency-division transmission or code-division transmission. For this reason, for example, when a transmission signal is transmitted from each transmission antenna and the Doppler frequency (that is, the relative speed of the target) is detected from a change in the reception phase of the transmission signal as in Patent Literature 2, it is necessary to detect the Doppler frequency. When the Fourier frequency analysis is applied to (1), the time interval (for example, the sampling interval) of the observation of the change in the reception phase becomes long. Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing (that is, the relative speed range of the target that can be detected) is reduced.

  In addition, when a reflected wave signal from a target exceeding a Doppler frequency range (in other words, a relative velocity range) in which Doppler frequency can be detected without aliasing is assumed, the radar device determines whether or not the reflected wave signal is an aliasing component. No, an ambiguity (Ambiguity) of Doppler frequency (in other words, relative velocity of the target) occurs.

  For example, when a radar apparatus transmits a transmission signal (transmission pulse) while sequentially switching Nt transmission antennas at a predetermined period Tr, the transmission apparatus transmits Tr × Nt transmission signals until transmission signals are transmitted from all transmission antennas. Transmission time is required. When such time division multiplex transmission is repeated Nc times and Fourier frequency analysis is applied for Doppler frequency detection, the Doppler frequency range in which Doppler frequency can be detected without aliasing is ± 1 / (2Tr × Nt). Therefore, the Doppler frequency range in which the Doppler frequency can be detected without aliasing decreases as the number Nt of transmitting antennas increases, and the ambiguity of the Doppler frequency easily occurs even at a lower relative speed.

  Here, as one of the methods for expanding the Doppler frequency range (in other words, the relative speed range or the maximum value of the relative speed), there is a method in which one transmission antenna is used (one branch) and a virtual reception array is not formed. In this method, the transmission time (transmission cycle) of Tr × Nt can be shortened by one transmission antenna (Nt = 1), so that the Doppler frequency range (or the maximum value of the relative speed) can be expanded. However, according to this method, the antenna aperture area becomes small, and the accuracy of separation and estimation of the distance or azimuth decreases.

  As another method for expanding the Doppler frequency range (or the maximum value of the relative speed), there is a method of using one transmitting antenna (one branch) and widening the element spacing of the receiving antenna. In this method, the transmission time (transmission cycle) of Tr × Nt can be shortened by one transmission antenna (Nt = 1), so that the Doppler frequency range (or the maximum value of the relative speed) can be expanded. Further, the antenna aperture area can be increased by increasing the element spacing of the receiving antenna. However, in this method, the grating lobe becomes large due to the element spacing of the receiving antenna, and erroneous detection (for example, occurrence of ghost) increases.

  Therefore, in one aspect according to the present disclosure, the Doppler frequency range (or the maximum value of the relative velocity) in which aliasing does not occur (in other words, in which ambiguity does not occur) is suppressed while reducing the antenna aperture area or increasing the grating lobe. A method for enlarging will be described. Accordingly, in one aspect according to the present disclosure, the radar device 10 can accurately detect a target in a wider Doppler frequency range.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and the description thereof will not be repeated.

  Hereinafter, a configuration in which a radar apparatus transmits different time-division multiplexed transmission signals from a plurality of transmission antennas in a transmission branch and separates each transmission signal and performs reception processing in a reception branch (in other words, a MIMO radar) Configuration) will be described.

[Configuration of radar device]
FIG. 1 is a block diagram showing a configuration of a radar device 10 according to the present embodiment.

  The radar device 10 includes a radar transmission unit (transmission branch) 100, a radar reception unit (reception branch) 200, and a reference signal generation unit 300.

  The radar transmitter 100 generates a high-frequency (radio frequency) radar signal (radar transmission signal) based on the reference signal received from the reference signal generator 300. Then, radar transmitting section 100 transmits a radar transmission signal at a predetermined transmission cycle using a transmission array antenna constituted by a plurality of transmission antennas 108-1 to 108-Nt.

  The radar receiving unit 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (target, not shown), using a receiving array antenna including a plurality of receiving antennas 202-1 to 202-Na. The radar receiving unit 200 performs a process synchronized with the radar transmitting unit 100 by performing the following processing operation using the reference signal received from the reference signal generating unit 300. Further, the radar receiver 200 performs signal processing on the reflected wave signal received by each of the receiving antennas 202, and performs, for example, detection of the presence or absence of a target or estimation of the arrival direction of the reflected wave signal.

  The target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including four wheels and two wheels), a person, a block, a curb, and the like.

  The reference signal generator 300 is connected to each of the radar transmitter 100 and the radar receiver 200. The reference signal generation unit 300 supplies a reference signal as a reference signal to the radar transmission unit 100 and the radar reception unit 200, and synchronizes the processes of the radar transmission unit 100 and the radar reception unit 200.

[Configuration of Radar Transmitter 100]
The radar transmission unit 100 includes a radar transmission signal generation unit 101, a switching control unit 105, a transmission switching unit 106, transmission radio units 107-1 to 107-Nt, and transmission antennas 108-1 to 108-Nt. Have. That is, radar transmitting section 100 has Nt transmitting antennas 108, and each transmitting antenna 108 is connected to individual transmitting radio section 107.

  The radar transmission signal generation unit 101 generates a timing clock obtained by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. Then, the radar transmission signal generation unit 101 repeatedly outputs a radar transmission signal at a predetermined radar transmission cycle (Tr). The radar transmission signal is represented by y (k, M) = I (k, M) + jQ (k, M). Here, j represents an imaginary unit, k represents a discrete time, and M represents an ordinal of a radar transmission cycle. Further, I (k, M) and Q (k, M) are an in-phase component (In-Phase component) and a quadrature component of the radar transmission signal (k M) at the discrete time k in the M-th radar transmission cycle. (Quadrature component).

  The radar transmission signal generation unit 101 includes a code generation unit 102, a modulation unit 103, and an LPF (Low Pass Filter) 104. Hereinafter, each component of the radar transmission signal generation unit 101 will be described.

Specifically, the code generation unit 102 generates a code a _n (M) (n = 1,..., L) (pulse code) of a code sequence having a code length L for each radar transmission cycle Tr. As the code a _n (M) generated by the code generation unit 102, for example, a code that provides a low range side lobe characteristic is used. Examples of the code sequence include a Barker code, an M-sequence code, and a Gold code.

Modulation section 103, the pulse code sequence received from the code generation unit 102 (e.g., code a _n (M)) pulse modulation on (amplitude modulation, ASK (Amplitude Shift Keying), pulse shift keying) or phase modulation (Phase Shift Keying) and outputs a modulated signal to the LPF 104.

  LPF 104 outputs, to the transmission switching unit 106, a signal component of a predetermined limited band or less, of the modulated signal received from the modulation unit 103, as a baseband radar transmission signal.

  FIG. 2 shows an example of a radar transmission signal generated by the radar transmission signal generation unit 101. As shown in FIG. 2, a pulse code sequence having a code length L is included in the code transmission section Tw in the radar transmission cycle Tr. In each radar transmission cycle Tr, a pulse code sequence is transmitted during the code transmission section Tw, and the remaining section (Tr-Tw) is a non-signal section. One code includes L sub-pulses. Further, by performing pulse modulation using No samples per subpulse, Nr (= No × L) samples of signals are included in each code transmission section Tw. Further, a null signal section (Tr-Tw) in the radar transmission cycle Tr includes Nu samples.

  The switching control unit 105 controls the transmission switching unit 106 in the radar transmitting unit 100 and the output switching unit 211 in the radar receiving unit 200. The control operation of the switching control unit 105 for the output switching unit 211 of the radar receiving unit 200 will be described later in the description of the operation of the radar receiving unit 200. Hereinafter, a control operation of the transmission control unit 106 of the radar transmitting unit 100 in the switching control unit 105 will be described.

  The switching control unit 105 outputs a control signal (hereinafter, referred to as a “switching control signal”) for switching the transmitting antenna 108 (in other words, the transmitting wireless unit 107) to the transmission switching unit 106 for each radar transmission cycle Tr, for example. .

  The transmission switching unit 106 performs a switching operation of outputting the radar transmission signal input from the radar transmission signal generation unit 101 to the transmission radio unit 107 specified by the switching control signal input from the switching control unit 105. For example, the transmission switching unit 106 selects and switches one of the plurality of transmission radio units 107-1 to 107-Nt based on the switching control signal, and outputs a radar transmission signal to the selected transmission radio unit 107. I do.

  The z-th (z = 1,..., Nt) -th transmission radio section 107 performs frequency conversion on a baseband radar transmission signal output from the transmission switching section 106 to perform carrier frequency (Radio Frequency: RF) band. , Is amplified to a predetermined transmission power P [dB] by the transmission amplifier, and is output to the z-th transmission antenna 108.

  The z-th (z = 1,..., Nt) -th transmission antenna 108 radiates a radar transmission signal output from the z-th transmission radio unit 107 into space.

  FIG. 3 shows an example of a switching operation of transmitting antenna 108 according to the present embodiment. The switching operation of transmitting antenna 108 according to the present embodiment is not limited to the example shown in FIG.

  In FIG. 3, the switching control unit 105 switches from the first transmission antenna 108 (or the transmission radio unit 107-1) to the Nt-th transmission antenna 108 (or the transmission radio unit 107-Nt) for each radar transmission cycle Tr. A switching control signal indicating an instruction to switch in order is output to transmission switching section 106. Therefore, in each of the first to Nt-th transmission antennas 108, a radar transmission signal is transmitted at a transmission interval of Np (= Nt × Tr) cycles.

  The switching control unit 105 performs control to repeat the switching operation of the transmission radio unit 107 in the antenna switching period Np Nc times.

Note that the transmission start time of the transmission signal in each transmission radio section 107 does not have to be synchronized with the cycle Tr. For example, each transmission radio section 107 may start transmission of a radar transmission signal by providing different transmission delays Δ ₁ , Δ ₂ ,..., _ΔNt at the transmission start time. When such transmission delays Δ ₁ , Δ ₂ ,..., Δ _Nt are provided, a transmission phase correction coefficient considering the transmission delays Δ ₁ , Δ _{2 ,.} By doing so, it is possible to eliminate the effect of different phase rotation depending on the Doppler frequency. By varying such transmission delays Δ ₁ , Δ ₂ ,..., Δ _Nt for each measurement, when there is interference from another radar device (not shown) or when interference is given to another radar device, Thus, the effect of randomizing the influence of interference between other radars can be obtained.

  Further, the radar transmission unit 100 may include a radar transmission signal generation unit 101a shown in FIG. 4 instead of the radar transmission signal generation unit 101. The radar transmission signal generation unit 101a does not include the code generation unit 102, the modulation unit 103, and the LPF 104 illustrated in FIG. 1, but includes a code storage unit 111 and a DA conversion unit 112 instead. The code storage unit 111 stores in advance a code sequence generated by the code generation unit 102 (FIG. 1), and sequentially reads out the stored code sequences cyclically. The DA converter 112 converts a code sequence (digital signal) output from the code storage unit 111 into an analog signal (baseband signal).

[Configuration of Radar Receiver 200]
In FIG. 1, a radar receiving unit 200 includes Na receiving antennas 202 and constitutes an array antenna. Further, radar receiving section 200 includes Na antenna system processing sections 201-1 to 201-Na, CFAR section 213, and direction estimation section 214.

  Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected on a target, and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

  Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 207.

  The reception radio section 203 includes an amplifier 204, a frequency converter 205, and a quadrature detector 206. The reception radio unit 203 generates a timing clock that is a predetermined number times the reference signal received from the reference signal generation unit 300, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies a reception signal received from the reception antenna 202 to a predetermined level, the frequency converter 205 frequency-converts a high-frequency band reception signal to a baseband band, and the quadrature detector 206 The baseband reception signal is converted into a baseband reception signal including an I signal and a Q signal by detection.

  The signal processing unit 207 of each antenna system processing unit 201-z (where z = 1 to Na) includes AD conversion units 208 and 209, a correlation calculation unit 210, an output switching unit 211, and a Doppler analysis unit. 212-1 to 212-Nt.

  The I signal is input to the AD converter 208 from the quadrature detector 206, and the Q signal is input to the AD converter 209 from the quadrature detector 206. The AD converter 208 converts the I signal into digital data by sampling the baseband signal including the I signal in discrete time. The AD converter 209 converts the Q signal into digital data by sampling the baseband signal including the Q signal in discrete time.

  Here, in the sampling of the AD converters 208 and 209, for example, Ns discrete samples are performed per time Tp (= Tw / L) of one subpulse in the radar transmission signal. That is, the number of oversamples per sub-pulse is Ns.

In the following description, the I-th signal I _z (k, M) and the Q signal Q _z (k, M) are used to output the M-th radar transmission cycle Tr [M] as the output of the AD converters 208 and 209. The received signal of the baseband at the discrete time k is represented as a complex signal x _z (k, M) = I _z (k, M) + j Q _z (k, M) (however, z = 1 to Na). . In the following, the discrete time k is based on the timing at which the radar transmission cycle (Tr) starts (k = 1), and the signal processing unit 207 is a sample point k before the end of the radar transmission cycle Tr. = (Nr + Nu) Ns / No. That is, k = 1,..., (Nr + Nu) Ns / No. Here, j is an imaginary unit.

The correlation operation unit 210 in the z-th (z = 1,..., Na) -th signal processing unit 207 outputs the discrete sample values I _z (k, M) received from the AD conversion units 208 and 209 for each radar transmission cycle Tr. Q _z (k, M) discrete sample values x _z (k, M) comprising a pulse code a _n of the code length L to be transmitted in a radar transmitter 100 (M) (except, z = 1, ..., Na , N = 1,..., L). For example, the correlation operation unit 210 performs a sliding correlation operation between the discrete sample value x _z (k, M) and the pulse code a _n (M). For example, the correlation operation value AC _z (k, M) of the sliding correlation operation at the discrete time k in the M-th radar transmission cycle Tr [M] is calculated based on the following equation.

  In the above formula, an asterisk (*) represents a complex conjugate operator.

  The correlation calculation unit 210 performs the correlation calculation over a period of k = 1,..., (Nr + Nu) Ns / No, for example, according to Expression (1).

  The correlation calculation unit 210 is not limited to the case where the correlation calculation is performed on k = 1,..., (Nr + Nu) Ns / No, but performs the measurement in accordance with the existence range of the target to be measured by the radar device 10. The range (ie, the range of k) may be limited. Thereby, in the radar device 10, the amount of calculation processing of the correlation calculation unit 210 can be reduced. For example, the correlation calculator 210 may limit the measurement range to k = Ns (L + 1),..., (Nr + Nu) Ns / No-NsL. In this case, as shown in FIG. 5, the radar device 10 does not perform measurement in a time section corresponding to the code transmission section Tw.

  Thereby, even when the radar transmission signal directly wraps around to the radar receiving unit 200, the processing by the correlation calculation unit 210 is not performed during the period when the radar transmission signal wraps around (at least a period less than τ1). Therefore, it is possible to perform measurement without the influence of the wraparound. When the measurement range (the range of k) is limited, the processing of the output switching unit 211, the Doppler analysis unit 212, the CFAR unit 213, and the direction estimation unit 214 described below is similarly performed on the measurement range (the range of k). It is only necessary to apply a process with a limited range. As a result, the amount of processing in each component can be reduced, and the power consumption in the radar receiver 200 can be reduced.

The output switching unit 211 selectively outputs the output of the correlation operation unit 210 for each radar transmission cycle Tr to one of the Nt Doppler analysis units 212 based on the switching control signal input from the switching control unit 105. Switch to and output. Hereinafter, as an example, the switching control signal in the M-th radar transmission cycle Tr [M] is represented by Nt bit information [bit ₁ (M), bit ₂ (M),..., Bit _Nt (M)]. For example, in the switching control signal of the M-th radar transmission cycle Tr [M], if the ND bit (where ND = 1 to Nt) is “1”, the output switching unit 211 outputs the ND bit. The second Doppler analyzer 212 is selected (in other words, turned on). On the other hand, when the ND bit is “0” in the switching control signal of the M-th radar transmission cycle Tr [M], the output switching unit 211 does not select the ND-th Doppler analysis unit 212 (in other words, OFF). The output switching unit 211 outputs the correlation operation value AC _z (k, M) input from the correlation operation unit 210 to the selected Doppler analysis unit 212.

For example, an Nt-bit switching control signal corresponding to the switching operation of transmission radio section 107 (or transmission antenna 108) shown in FIG.
[bit ₁ (1), bit ₂ (1),…, bit _Nt (1)] = [1, 0,…, 0]
[bit ₁ (2), bit ₂ (2),…, bit _Nt (2)] = [0, 1,…, 0]
…
[bit ₁ (Nt), bit ₂ (Nt),…, bit _Nt (Nt)] = [0, 0,…, 1]

  As described above, each Doppler analyzer 212 is sequentially selected in Np (= Nt × Tr) cycles (in other words, it is turned ON). For example, the switching control signal repeats the above content Nc times.

  The z-th (z = 1,..., Na) -th signal processing unit 207 includes Nt Doppler analysis units 212.

The Doppler analysis unit 212 performs a Doppler analysis on the output from the output switching unit 211 (for example, the correlation operation value AC _z (k, M)) for each discrete time k. For example, when Nc is a power of 2, fast Fourier transform (FFT) processing can be applied in Doppler analysis.

For example, of the w-th output of the ND-th Doppler analyzer 212 of the z-th signal processor 207, the output of a virtual receiving array to be superimposed, which will be described later, is at discrete time k as shown in the following equation. Doppler frequency response FT_CI _z ^(ND) of the Doppler frequency index _{f s (k, f s,} w) indicates a. Note that ND = 1 to Nt, k = 1,..., (Nr + Nu) Ns / No, and w is an integer of 1 or more. _Nva indicates the number of antennas corresponding to the virtual reception array to be superimposed, and N indicates the number of transmissions in one cycle. Further, j is an imaginary unit, and z = 1 to Na.

As an example, a case where the antenna arrangement and the transmission interval shown in FIGS. 7 and 8 are used (details will be described later) will be described. In FIGS. 7 and 8, the set of the superimposed virtual reception arrays (VA # 4, VA # 7, VA # 9) is sampled at a period T '. Therefore, when ND = 1, 2, 3, and z = 4, 3, 1, Equation (2) is represented by the following equation. In equation (3), N _va = 3 and N = 3.

As another example, a case where the antenna arrangement and the transmission interval shown in FIGS. 9, 10, 11 and 12 are used (details will be described later) will be described. 9, 10, 11, and 12, the set of virtual arrays (VA # 11 and VA # 18) to be superimposed is sampled at a period T ′ = 3Tr. Therefore, when ND = 2 and z = 3, and when ND = 3 and z = 2, equation (2) is represented by the following equation. In equation (4), N _va = 2 and N = 6.

On the other hand, for example, among the w-th output in the ND-th Doppler analyzer 212 of the z-th signal processor 207, the output in the non-superimposed virtual reception array other than the superimposed virtual reception array is expressed by the following equation. as shown, shows a Doppler frequency response FT_CI _z Doppler frequency index f _u at discrete time ^{k (ND) (k, f} u, w). Note that ND = 1 to Nt, k = 1,..., (Nr + Nu) Ns / No, and w is an integer of 1 or more. Further, j is an imaginary unit, and z = 1 to Na.

  At the time of the FFT processing, the Doppler analysis unit 212 may multiply a window function coefficient such as a Han window or a Hamming window, for example. By using the window function coefficient, side lobes generated around the frequency peak can be suppressed.

  The processing in each component of the signal processing unit 207 has been described above.

In FIG. 1, the CFAR unit 213 performs CFAR (Constant False Alarm Rate) processing (in other words, adaptive threshold value determination) using the output from the Doppler analysis unit 212, and obtains a discrete time index k_ for giving a peak signal. _{Extract cfar} and Doppler frequency index _{fs_cfar} .

For example, CFAR portion 213 of each of the antenna system processing units 201-1 to _{201-N a} Doppler analysis unit 213, the output FT_CI _z ^{(ND) (k} corresponding to the virtual receiving array to be superimposed (details will be described later) , f _s , w) to perform CFAR processing.

Further, the CFAR unit 213 calculates the Doppler frequency index f _{s_cfar} corresponding to the virtual receiving array to be superimposed on the output FT_CI _z ^(ND) (k ^{) of} the Doppler analyzing unit 213 corresponding to another virtual receiving array other than the virtual receiving array to be superimposed. , f _u, in order to correspond to the Doppler frequency index f _u of w), to index conversion. The index conversion may be performed by Expressions (6) and (7). The CFAR unit 213 outputs the Doppler frequency index f _{s_cfar} after the index conversion to the direction estimating unit 214.

Here, f _{s_cfar} = − (Nt−1) Nc / 2 + 1, .., 0, ..., (Nt−1) Nc / 2, and _{fu_cfar} = −Nc / 2 + 1, .. , 0, ..., Nc / 2.

Hereinafter, the Doppler frequency index f _{s_cfar} having a wide Doppler frequency range is _referred to as a wide range Doppler frequency index f _{s_cfar} . Furthermore, a narrow Doppler frequency index f _u of the Doppler frequency range, expressed as the narrow range Doppler frequency index f _u. When the wide-range Doppler frequency index f _{s_cfar} is made to correspond to the narrow-range Doppler frequency index f _u , there is a possibility that an overlap is included.

For example, a wide range Doppler frequency index f _{S_cfar,} if it contains 0 ≦ α ≦ Nc / 2 in the range Doppler frequency index alpha of the index conversion to correspond to a narrow range Doppler frequency index f _u, is converted alpha. Here, if β = α−Nc is also included in the wide-range Doppler frequency index _{fs_cfar} , β corresponds to the narrow-range Doppler frequency index f _u because β is included in the range of −Nc ≦ β ≦ −Nc / 2. Is converted to β + Nc = α. Thus, a wide range Doppler frequency index f _{S_cfar,} the index conversion to correspond to a narrow range Doppler frequency index f _u, overlapping occurs.

Similarly, a wide range Doppler frequency index f _{S_cfar,} when β = α + Nc is also included, beta, since it is within the scope of Nc ≦ β ≦ 3Nc / 2, the index conversion to correspond to a narrow range Doppler frequency index f _u , Β + Nc = α. Therefore, the index conversion to correspond to a narrow range Doppler frequency index f _u, overlapping occurs.

As described above, when the wide-range Doppler frequency index f _{s_cfar} includes α and β in which | α−β | is an integral multiple of Nc, overlapping occurs when the wide-range Doppler frequency index f _{s_cfar} corresponds to the narrow-range Doppler frequency index f _u. I do.

When duplicate narrow range Doppler frequency index f _u is occurring, the signal component of the narrow range Doppler frequency index f _u is in a state in which signals of different Doppler frequency components have been mixed. The closer the power of the mixed signal is, the more the amplitude / phase component fluctuates, and the accuracy of the angle measurement in the subsequent direction estimating unit 214 may deteriorate. Therefore, in the present embodiment, an overlap determination process is introduced. This suppresses the influence of the direction estimating unit 214 causing deterioration in the accuracy of the side angle. Next, the overlap determination processing will be described.

<Duplicate determination process>
The w-th output FT_CI _z ^(ND) from the Doppler analysis unit 212 corresponding to the virtual reception array in which the Doppler frequency index α and the Doppler frequency index β are not superimposed among the wide range Doppler frequency index f _{s_cfar} extracted by the CFAR processing k, f _u, the index conversion to correspond to the Doppler frequency index f _u of w) do. If the converted Doppler frequency index _{fs_cfar} overlaps, the following processes (B1) to (B3) are performed.

(B1) The CFAR unit 213 outputs FT_CI ₁ ^(ND) (k, α, w),..., FT_CI _Na ^(ND) (k), which is the w-th output from the Doppler analysis unit 212 corresponding to the virtual reception array to be superimposed. , Α, w) and the power sum of FT_CI ₁ ^(ND) (k, β, w),..., FT_CI _Na ^(ND) (k, β, w).

  (B2) As a result of the comparison of the power sum in (B1), if there is a power difference equal to or more than a predetermined value (for example, set to about 6 to 10 dB), the CFAR unit 213 has a larger power among the Doppler frequency indexes α and β. The lower Doppler frequency index is made valid, and the lower Doppler frequency index is excluded from the output target to the direction estimation unit 214.

  (B3) The CFAR unit 213 excludes both the Doppler frequency indexes α and β from the output target to the direction estimating unit 214 when there is no power difference equal to or more than the predetermined value as a result of the power sum comparison of (B1). .

  The processing of the CFAR unit 213 has been described above. Note that the radar apparatus 10 may perform the direction estimation processing in the direction estimation unit 214 without performing the CFAR processing.

In Figure 1, the direction estimating unit 214, information inputted from the CFAR section 213 (e.g., time index k_ _CFAR, and Doppler frequency index _{f s _ cfar, f u _} cfar) based on the respective Doppler analysis unit 212 Is used to perform target direction estimation processing.

Incidentally, for example, the direction estimating unit 214 generates Expression virtual reception array correlation vector h as shown in _{(8) (k, f s} , w), performs the direction estimation process.

The following summarizes the w-th outputs from the Doppler analyzers 212-1 to 212-Nt obtained by performing similar processing in the respective signal processors 207 of the antenna system processors 201-1 to 201-Na. _Is expressed as a virtual received array correlation vector h ( _{k_cfar} , _{f_cfar} , w) including Nt × Na elements which are the product of the number Nt of transmitting antennas and the number Na of receiving antennas as shown in Expression (8). I do. The virtual reception array correlation vector h ( _{k_cfar} , _{f_cfar} , w) is used for processing for estimating the direction of the reflected wave signal from the target based on the phase difference between the reception antennas 202. Here, z = 1,..., Na, and ND = 1,.

In Equation (8), h _{cal [b]} is an array correction value for correcting a phase deviation and an amplitude deviation between the transmission array antennas and between the reception array antennas. b = 1,..., Nt × Na. Further, in the equation (8), the virtual reception array pairs (ND, z) which overlaps a the _{f_} cfar = f s_cfar, the set of virtual reception array which does not overlap (ND, z) is the _{f_} cfar = f u_cfar.

Further, since the transmission antenna 108 is switched in a time division manner, different phase rotations occur at different Doppler frequencies f. TxCAL ⁽¹⁾ (f),..., TxCAL ^(Nt) (f) are transmission phase correction coefficients for correcting the phase rotation to match the phase of the reference transmission antenna.

For example, when the first transmission antenna 108 (ND = 1) is used as a reference transmission antenna, which corresponds to the switching operation of the transmission radio unit 107 (or transmission antenna 108) shown in FIG. It is represented by

Note that the transmission delay delta ₁ which different transmission start time of the transmission signal of each transmission radio section _107, delta _2, ..., the case of providing the delta _Nt, transmission phase correction coefficient TxCAL shown in equation ^{(9) (ND) (f} ) to multiply the correction coefficient Δ _TxCAL ^{(ND) (f)} of formula (10) may be a new transmission phase correction coefficient TxCAL ^{(ND) (f).} As a result, the influence of the phase rotation that differs depending on the Doppler frequency can be removed. Here, ^{ND of} Δ _TxCAL ^(ND) (f) is a reference transmission antenna number used as a phase reference.

The virtual reception array correlation vector h (k _cfar , f _{s — cfar} , w) is a column vector composed of Na × Nt elements.

The direction estimating unit 214 calculates and calculates a spatial profile with the azimuth direction θ in the direction estimation evaluation function value P _H (θ _{BEAM_cfar} , k _cfar , f _s _ _cfar , w) being variable within a predetermined angle range, for example. A predetermined number of maximal peaks in the spatial profile are extracted in descending order, and the direction of the maximal peak is output as an estimated direction of arrival.

Note that there are various methods for the direction estimation evaluation function value P _H (θ _{BEAM_cfar} , k _cfar , f _s _ _cfar , w) depending on the arrival direction estimation algorithm. For example, an estimation method using an array antenna disclosed in Non-Patent Document 3 may be used.

For example, when Nt × Na virtual reception arrays are linearly arranged at equal intervals d _H , the beamformer method can be expressed as follows. Other methods such as Capon and MUSIC are also applicable.

Here, in equation (11), the superscript H is a Hermitian transpose operator. A (θ _u ) indicates the direction vector of the virtual reception array with respect to the arriving wave in the azimuth direction θ _u .

The azimuth direction θ _u is a vector obtained by changing the azimuth range in which the arrival direction is estimated at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
θ _u = θmin + uβ ₁ , u = 0, ..., NU
NU = floor [(θmax-θmin) / β ₁ ] +1
Here, floor (x) is a function that returns the maximum integer value not exceeding the real number x.

Note that the above-described time information k may be converted into distance information and output. The following equation may be used to convert the time information k into the distance information R (k). Here, Tw represents a code transmission section, L represents a pulse code length, and C ₀ represents a light speed.

The Doppler frequency information may be converted into a relative velocity component and output. To convert the Doppler frequency index f _s into a relative velocity component v _d (f _s ), the conversion can be performed using the following equation. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmission radio section 107. Further, the delta _f, a Doppler frequency interval by the FFT processing in the Doppler analysis unit 212. For example, in this embodiment, a _{Δ f = 1 / (NtNcTr)} .

  The operation of the direction estimating unit 214 has been described above.

[Operation of radar device 10]
The operation of the radar device 10 having the above configuration will be described.

  The Nt transmission antennas 108 (transmission array) and the Na reception antennas 202 (reception array) are arranged, for example, so as to satisfy the following (condition 1), and transmit timing so as to satisfy the following (condition 2). Can be switched.

  (Condition 1) Transmission is performed such that at least two virtual antennas are arranged at the same position (overlap or overlap) among Nt × Na antenna elements (referred to as virtual antennas or virtual branches) constituting a virtual reception array. Antenna 108 and receiving antenna 202 are arranged.

  (Condition 2) The transmission intervals of the radar transmission signals sequentially transmitted from the transmission antennas 108 corresponding to the virtual antennas whose arrangement positions overlap each other are equal.

  First, regarding (condition 2), the transmission timing of a radar transmission signal will be described.

  6A, 6B, and 6C show an example of the transmission timing of the radar transmission signals from the plurality of transmission antennas 108. In FIGS. 6A, 6B, and 6C, as an example, it is assumed that the number of transmission antennas 108 is Nt = 6 (for example, Tx # 1 to Tx # 6).

  If the transmission timing of the radar transmission signal (in other words, the number of transmissions) is N times within the transmission period T (for example, T = Tr × Nt) of each transmission antenna 108, to satisfy (condition 2), The transmission interval (in other words, the transmission cycle) T ′ between the transmission antennas corresponding to the virtual antennas in which the overlaps occur is as follows: (1) One cycle in the number of transmissions corresponding to a divisor of N in one transmission cycle T, or , (2) N out of N cycles (in other words, all transmission times).

  For example, as shown in FIG. 6A, FIG. 6B and FIG. 6C, when N = 6 (divisor: 2 and 3), in one transmission cycle T = 6Tr, the transmission cycle of the transmission antenna corresponding to the virtual antenna whose arrangement position overlaps T ′ is one cycle for three transmissions as shown in FIG. 6A (in other words, T ′ = T / 2), and one cycle for two transmissions as shown in FIG. Then, T ′ = T / 3), or N times N times as shown in FIG. 6C (in other words, T ′ = T / 6).

  For example, in the radar device 10, the transmission cycle T 'is set according to the number of transmission antennas (for example, approximately several N or N) corresponding to the virtual antennas whose arrangement positions overlap.

  For example, as shown in FIG. 6A, when the transmitting antennas 108 corresponding to the virtual antennas whose arrangement positions overlap each other are two of Tx # 1 and Tx # 4 (a divisor of N = 6), Tx # 1 and Tx # The transmission interval T ′ of 4 is T / 2. Therefore, in the reception processing, the radar apparatus 10 can set the sampling interval at the virtual antenna having the overlapping position to the transmission interval T '= T / 2 of Tx # 1 and Tx # 4.

  Further, as shown in FIG. 6B, when the number of transmitting antennas 108 corresponding to the virtual antennas whose arrangement positions overlap each other is Tx # 1, Tx # 3, and Tx # 5 (N = divisor of 6), Tx # 1, the transmission interval T 'between Tx # 3 and Tx # 5 is T / 3. Therefore, in the reception process, the radar apparatus 10 can set the sampling interval at the virtual antenna having the overlapping arrangement position to the transmission interval T '= T / 3 of Tx # 1, Tx # 3, and Tx # 5.

  Further, as shown in FIG. 6C, when the transmission antennas 108 corresponding to the virtual antennas whose arrangement positions overlap each other are all (N) of Tx # 1 to Tx # 6, the transmission interval T of Tx # 1 to Tx # 6 'Becomes T / 6. Therefore, in the reception processing, the radar apparatus 10 can set the sampling interval at the virtual antenna having the overlapping position to the transmission interval T '= T / 6 of Tx # 1 to Tx # 6.

For example, when the sampling interval is the transmission interval T of each transmitting antenna 108, it is represented by the maximum value of the relative speed v _max = λ / (4T). Here, λ indicates the wavelength of the carrier frequency, and T indicates the sampling interval.

On the other hand, for example, in FIG. 6A, when the transmission interval T ′ = T / 2 is set as the sampling interval at the virtual antenna where the arrangement positions overlap, the relative velocity maximum value v ′ _max = λ / 4T ′ = 2v It is represented by _max . Similarly, for example, in FIG. 6B, when the transmission interval T ′ = T / 3 is set as the sampling interval at the virtual antenna having the overlapping position, the maximum relative speed v ′ _max = λ / 4T ′ = 3v _max . expressed. Similarly, for example, in FIG. 6C, when the transmission interval T ′ = T / 6 is set as the sampling interval at the virtual antenna having the overlapping position, the maximum relative speed v ′ _max = λ / 4T ′ = 6v _max . expressed.

As described above, in FIGS. 6A, 6B, and 6C, by setting the transmission intervals of the radar transmission signals sequentially transmitted from the plurality of transmission antennas 108 corresponding to the virtual antennas whose arrangement positions overlap with each other, the relative speed is increased. the maximum value v _'max (or Doppler frequency range) of about several times the N maximum value v _max of the relative speed based on the transmission interval T of each transmitting antenna 108 (or Doppler frequency range), or, N times It is expanded to. Therefore, in the radar device 10, the Doppler frequency range in which the Doppler frequency can be detected without aliasing can be expanded, and the occurrence of Doppler frequency ambiguity can be prevented.

  The radar device 10 transmits a radar transmission signal using a plurality of transmission antennas 108 in a predetermined transmission pattern. For example, the transmission pattern (in other words, the switching pattern indicated by the switching control signal) of the transmitting antenna 108 that transmits the radar transmission signal at a plurality of transmission timings (for example, N times) within the transmission period T is different for each of the transmission periods T Is repeated. In the radar device 10, the transmission pattern (in other words, the switching pattern indicated by the switching control signal) of the transmission antenna 108 that transmits the radar transmission signal at a plurality of transmission timings (for example, N times) within the transmission cycle T is transmitted by the transmission It is repeated every cycle T.

  Next, regarding (Condition 1), a specific example of the antenna arrangement according to the present embodiment will be described. Hereinafter, as an example, an arrangement example 1 and an arrangement example 2 which are specific examples of the antenna arrangement will be described.

<Arrangement example 1>
In the first arrangement example, a case will be described where the transmitting antenna 108 and the receiving antenna 202 are each arranged one-dimensionally.

  FIG. 7 shows an example of an antenna arrangement according to arrangement example 1.

  In FIG. 7, the number of transmitting antennas 108 is Nt = 3 (for example, Tx # 1, Tx # 2, and Tx # 3), and the number of receiving antennas 202 is Na = 4 (for example, Rx # 1, Rx # 2, Rx # 3 and Rx # 4).

  In FIG. 7, for example, the interval between Tx # 1 and Tx # 3 is the same as the interval between Rx # 1 and Rx # 4. In FIG. 7, for example, the interval between Tx # 3 and Tx # 2 is the same as the interval between Rx # 1 and Rx # 3.

  In this case, as shown in FIG. 7, in the virtual reception array arrangement (Nt × Na = 12 VA # 1 to VA # 12), a virtual antenna VA # 4 configured by Tx # 1 and Rx # 4, A virtual antenna VA # 7 constituted by Tx # 2 and Rx # 3 and a virtual antenna VA # 9 constituted by Tx # 3 and Rx # 1 are arranged at the same position so as to overlap.

  For example, the radar apparatus 10 is configured such that the transmission intervals of the transmission antennas Tx # 2 and Tx # 3 corresponding to the virtual antennas VA # 11 and VA # 18, which are respectively arranged at the same position, are equal. The transmission timing of the transmission antenna 108 is switched. For example, FIG. 8 illustrates each virtual antenna (VA # 1 to VA # 12) in the case where the transmission timing of the radar transmission signal is sequentially switched at Tx # 1, Tx # 2, and Tx # 3 illustrated in FIG. 4) shows the reception timing of the reflected wave signal (in other words, the transmission timing of each transmitting antenna 108).

  As shown in FIG. 8, the radar transmission signal is transmitted at a transmission interval T ′ in the order of Tx # 1, Tx # 2, and Tx # 3. Note that the transmission interval T of the radar transmission signal transmitted from each transmission antenna 108 is T = 3T ′ (in other words, T ′ = T / 3).

  Therefore, in FIG. 8, as in FIG. 6C, it is assumed that the arrangement positions overlap at all the transmission timings N = 3 times of the radar transmission signal within the transmission cycle T (for example, T = Tr × Nt) of each transmission antenna 108. Radar transmission signals are transmitted from transmission antennas 108 (for example, Tx # 1, Tx # 2, and Tx # 3) corresponding to the antennas (VA # 4, VA # 7, and VA # 9).

  As shown in FIG. 8, the radar device 10 receives a reflected wave signal corresponding to a radar transmission signal transmitted from Tx # 1, Tx # 2, and Tx # 3 at each transmission interval T '.

  Here, in FIG. 8, attention is paid to virtual antennas VA # 4, VA # 7, and VA # 9 whose arrangement positions overlap. As shown in FIG. 8, a reception signal is received at any one of the virtual antennas VA # 4, VA # 7, and VA # 9 for each transmission cycle T ′. Specifically, the radar apparatus 10 receives the reflected wave signal at VA # 4 at the transmission timing of Tx # 1, receives the reflected wave signal at VA # 7 at the transmission timing of Tx # 2, and receives the reflected wave signal at VA # 7 at the transmission timing of Tx # 3. At the transmission timing, a reflected wave signal is received at VA # 9. In other words, the radar apparatus 10 can receive the reflected wave signal at the same position of the virtual antenna at each transmission timing without waiting for the reception of the reflected wave signal of each transmission antenna 108 for each transmission cycle T. The radar device 10 performs Doppler analysis using signals received at the virtual antennas VA # 4, VA # 7, and VA # 9, for example.

  Thus, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position at every transmission interval T '. Therefore, for example, in FIG. 8, the radar apparatus 10 can set the sampling interval T ′ to T ′ = T / 3 at the arrangement position of the virtual antennas VA # 4, VA # 7, and VA # 9.

For example, when the sampling interval is the transmission interval T of each transmitting antenna 108, it is represented by the maximum value of the relative speed v _max = λ / 4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIG. 8, when the sampling intervals T ′ = T / 3 in the virtual antennas VA # 4, VA # 7, and VA # 9, the relative velocity maximum value _v′max = λ / 4T '= 3v _max .

Thus, in the arrangement example 1, the maximum value v ' _max (or Doppler frequency range) of the relative speed is expanded to three times the maximum value v _max of the relative speed based on the transmission interval T for each transmitting antenna 108.

<Arrangement example 2>
In the arrangement example 2, a case will be described where the transmitting antenna 108 and the receiving antenna 202 are respectively arranged two-dimensionally and the arrival direction is estimated three-dimensionally.

  FIG. 9 shows an example of the arrangement of the transmitting antennas 108 according to the example 2, and FIG. 10 shows an example of the arrangement of the receiving antennas 202 according to the example 2. FIG. 11 shows an example of an arrangement of a virtual reception array constituted by the transmission antenna 108 shown in FIG. 9 and the reception antenna 202 shown in FIG.

  In FIG. 9, the number of transmitting antennas 108 is Nt = 6 (for example, Tx # 1 to Tx # 6), and in FIG. 10, the number of receiving antennas 202 is Na = 8 (for example, Rx # 1 to Rx # 8). And

  As shown in FIGS. 9 and 10, the transmitting antenna 108 and the receiving antenna 202 are two-dimensionally arranged in the direction of the first axis and the direction of the second axis orthogonal to the first axis. For example, in FIG. 9, the two-dimensional layout relationship of Tx # 2 and Tx # 3 is the same as the two-dimensional layout relationship of Rx # 8 and Rx # 6 shown in FIG.

  In this case, as shown in FIG. 11, in a virtual receiving array arrangement (Nt × Na = 48 VA # 1 to VA # 48), a virtual antenna VA # 11 configured by Tx # 2 and Rx # 3, The virtual antenna VA # 18 constituted by Tx # 3 and Rx # 2 is arranged at the same position so as to overlap.

  For example, the radar apparatus 10 is configured such that the transmission intervals of the transmission antennas Tx # 2 and Tx # 3 corresponding to the virtual antennas VA # 11 and VA # 18, which are respectively arranged at the same position, are equal. The transmission timing of the transmission antenna 108 is switched. FIG. 12 shows an example of the transmission timing of each transmission antenna 108 for each virtual antenna (VA # 1 to VA # 12) shown in FIG.

  In FIG. 12, for example, in the transmission cycle T (for example, T = 6Tr) of each transmission antenna 108, the radar transmission signal is Tx # 2, Tx # 1, Tx # 4, Tx # 3, Tx # 5, and Tx #. Sent in the order of 6. Therefore, as shown in FIG. 12, the transmission interval T 'between Tx # 2 and Tx # 3 is T / 2, which is an equal interval. In FIG. 12, the transmission interval between Tx # 2 and Tx # 3 only needs to be T / 2, and the transmission order of each transmission antenna 108 is not limited to the order shown in FIG.

  Therefore, in FIG. 12, as in FIG. 6A, N is a divisor of N out of six transmission timings N of the radar transmission signal within the transmission cycle T (for example, T = Tr × Nt) of each transmission antenna 108. At this time, radar transmission signals are transmitted from transmission antennas 108 (for example, Tx # 2 and Tx # 3) corresponding to the virtual antennas (VA # 11 and VA # 18) whose arrangement positions overlap.

  In the virtual antennas VA # 11 and VA # 18 where the arrangement positions overlap, the radar apparatus 10 reflects the radar transmission signals transmitted from Tx # 2 and Tx # 3 corresponding to VA # 11 and VA # 18, respectively. Wave signals are received at transmission intervals T / 2. In other words, the radar device 10 can receive the reflected wave signal at the same position of the virtual antenna at every transmission interval T ′ = T / 2 without waiting for the reception of the reflected wave signal of each transmission antenna 108 for each transmission cycle T. . The radar apparatus 10 performs Doppler analysis using signals received at the virtual antennas VA # 11 and VA # 18, for example.

  Thus, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position at every transmission interval T '. Therefore, for example, in FIG. 12, the radar apparatus 10 can set the sampling interval T ′ to T ′ = T / 2 at the arrangement position of the virtual antennas VA # 11 and VA # 18.

For example, when the sampling interval is the transmission interval T of each transmitting antenna 108, it is represented by the maximum value of the relative speed v _max = λ / 4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIGS. 11 and 12, when the sampling interval T ′ = T / 2 in the virtual antennas VA # 11 and VA # 18, the maximum value of the relative speed v ′ _max = λ / 4T ′ = 2v _max .

Thereby, in the arrangement example 2, the maximum value v ' _max (or Doppler frequency range) of the relative speed is expanded to twice the maximum value v _max of the relative speed based on the transmission interval T for each transmitting antenna 108.

  The arrangement examples 1 and 2 of the antenna arrangement have been described above.

  The antenna arrangement (for example, the number of antennas Nt, Na or the arrangement position) is not limited to the examples shown in FIGS. 7, 9 and 10, and may be any antenna arrangement that satisfies the above (condition 1). I just need.

  Here, for example, in the virtual receiving array shown in FIG. 7, the gap between VA # 8 and VA # 12 is wider than the other virtual antennas. In the present embodiment, for example, the transmitting antenna 108 and the receiving antenna 202 may be arranged such that the number of missing points in the virtual receiving array is one or less. Thereby, it is possible to prevent the level of the side lobe or the grating lobe due to the toothless state from being increased (in other words, to be an unacceptable level).

  Other examples of the antenna arrangement will be described later in Variation 4.

  As described above, in the present embodiment, at least two virtual antennas among the virtual reception array including the plurality of virtual antennas configured based on the plurality of transmission antennas 108 and the plurality of reception antennas 202 in radar device 10 are described. To the same position. In the radar apparatus 10, the transmission intervals of the radar transmission signals between the transmission antennas 108 corresponding to at least two virtual antennas having the same arrangement position among the plurality of transmission antennas 108 are set to be equal.

  Thereby, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna at each transmission timing of the plurality of transmitting antennas 108 corresponding to the virtual antenna at the same arrangement position. Therefore, the radar apparatus 10 can shorten the reception interval at one virtual antenna as compared with the transmission interval for each transmission antenna 108. Therefore, the radar apparatus 10 can expand the Doppler frequency range (or the maximum value of the relative velocity) by shortening the sampling interval in the virtual antenna.

  Further, in the radar device 10, the transmission antenna 108 and the reception antenna 202 are arranged so that the arrangement positions of the virtual antennas corresponding to the respective transmission antennas 108 are overlapped by using the plurality of transmission antennas 108. As an example, in FIG. 7, if one transmission antenna (one branch) and four reception antennas (Rx # 1 to Rx # 4) of Tx # 1 are used, as described above, the transmission interval (in other words, Although the sampling interval can be shortened, the antenna aperture length is equivalent to four antennas. On the other hand, in the present embodiment, as described above, three transmitting antennas (three branches) Tx # 1 to Tx # 3 and four receiving antennas (Rx # 1 to Rx # 4) are used. The antenna aperture length can be reduced to 10 antennas while shortening the sampling interval.

  Thus, in the present embodiment, the above-described Doppler frequency range is widened in radar device 10 while increasing the antenna aperture area (or antenna aperture length) as compared with the case where one transmission antenna is used. it can.

  Further, in the present embodiment, by arranging the positions of the virtual antennas corresponding to the plurality of transmission antennas 108, the reception interval at the virtual antennas is shortened, and the Doppler frequency range is expanded. Therefore, in the present embodiment, in order to secure the antenna aperture area, for example, it is not necessary to increase the element spacing of the receiving antenna 202, so that the occurrence of grating lobes is suppressed, and the occurrence of erroneous detection (for example, occurrence of ghost) is suppressed. The increase can be suppressed.

  As described above, according to the present embodiment, the Doppler frequency range in which aliasing does not occur (in other words, in which ambiguity does not occur) is suppressed while reducing the antenna aperture area or increasing the grating lobe (or the maximum relative velocity). Value) can be expanded. Thereby, the radar device 10 can accurately detect the target (for example, the direction of arrival) in a wider Doppler frequency range.

(Variation 1 of Embodiment)
When the transmission timing (or the number of transmissions) is N times within the transmission cycle T of each transmission antenna 108, the transmission interval (or transmission cycle) T 'of the transmission antenna corresponding to the virtual antenna whose arrangement position is duplicated is as described above. As described above, (1) a cycle of once for the number of transmissions corresponding to a divisor of N, or (2) a cycle of all the number of transmissions of N.

  Variation 1 describes a case where the number Nt of transmission antennas 108 (for example, the number of transmissions N) is a prime number and there is no divisor of N.

  In the variation 1, when Nt is a prime number, for example, a number larger than Nt and not a prime number is set to N. For example, when Nt = 5, “6” which is a value (Nt + 1) that is one greater than Nt may be set to N. The transmission intervals between the transmission antennas 108 corresponding to the virtual antennas whose placement positions overlap can be made equal.

  In addition, in all N transmission timings within the transmission cycle T of each transmission antenna 108, a case where a radar transmission signal is transmitted from the transmission antenna 108 corresponding to the virtual antenna whose arrangement position overlaps (for example, see FIG. 6C) , Nt is a prime number (for example, Nt = 5), N is set to Nt. This is because, even when N = Nt, the transmission intervals between the transmission antennas 108 corresponding to the virtual antennas whose arrangement positions overlap can be made equal.

  Therefore, for example, when Nt = 5, the transmission cycle T ′ of the plurality of transmission antennas corresponding to the virtual antennas whose arrangement positions overlap is, for example, a divisor of N = 6 within one transmission cycle T (that is, 2 or Either one cycle for the number of transmissions of 3) or Nt cycles for N = Nt = 5.

  FIG. 13 shows the case where the number of transmissions of the transmission antenna corresponding to the virtual antenna whose arrangement position is duplicated is set to two (transmission period T ′ = T / 2) within one transmission period T when Nt = 5. It is an example of a transmission timing. In FIG. 13, transmission antennas Tx # 1 and Tx # 4 are transmission antennas corresponding to virtual antennas whose arrangement positions overlap.

  In the example shown in FIG. 13, the number of transmissions N in the transmission cycle T is six (= Nt + 1) for Nt = 5 (prime number). Therefore, in FIG. 13, the transmission intervals T 'of the two transmission antennas Tx # 1 and Tx # 4 are equal to T / 2. In FIG. 13, as an example, Tx # 5 transmits a radar transmission signal twice within one transmission cycle T. However, if the transmission timings of the transmission antennas Tx # 1 and Tx # 4 are equal intervals, the transmission antenna 108 that transmits the radar transmission signal a plurality of times in the transmission pattern within the transmission cycle T is a transmission antenna other than Tx # 5. 108 (for example, Tx # 2 or Tx # 3).

  According to Variation 1, even when the number Nt of the transmission antennas 108 is a prime number, the transmission intervals of the transmission antennas corresponding to the virtual antennas whose arrangement positions overlap can be made equal. Therefore, similarly to the above-described embodiment, the range of the Doppler frequency (the maximum value of the relative velocity) can be expanded, so that the radar apparatus 10 can suppress the reduction of the Doppler frequency range in which the Doppler frequency can be detected without aliasing. The direction of arrival can be accurately estimated.

  Although FIG. 13 illustrates the case where Nt = 5, the same applies to the case where the value of Nt is another prime number. Further, FIG. 13 illustrates the case where N = Nt + 1 when Nt = 5, but N is not limited to a value obtained by adding 1 to Nt.

  Further, in FIG. 13, as an example, a case has been described where the number of transmissions is set to two, which is a divisor of N, when N = Nt + 1 = 6, but the number of transmissions is other divisors. It may be three times or Nt times.

  For example, if N> Nt, if the number of transmissions of the transmitting antenna corresponding to the virtual antenna whose arrangement position in the transmission cycle T overlaps is 3 or more, the arrangement position in the transmission pattern of the transmission antenna 108 in the transmission cycle T May be set as the transmission antenna 108 that transmits the radar transmission signal a plurality of times (two or more times).

  FIG. 14A shows, as an example of N> Nt, when Nt = 5 and N = 6, transmission antennas (for example, Tx # 1 and Tx # 4) corresponding to virtual antennas whose arrangement positions overlap in the transmission cycle T. An example of the transmission timing when the number of transmissions in ()) is three is shown. In FIG. 14A, in the transmission pattern (or switching pattern) within the transmission cycle T, the transmission timing of Tx # 1 is set twice and the transmission timing of Tx # 4 is set once.

  Also, for example, when N> Nt, if the number of transmissions of the transmission antenna corresponding to the virtual antenna whose arrangement position in the transmission cycle T overlaps is 3 or more, in the transmission pattern of the transmission antenna 108 in the transmission cycle T, The transmitting antenna 108 that transmits the radar transmission signal a plurality of times may be a transmitting antenna other than the transmitting antenna farthest from the center of gravity in the arrangement of the plurality of transmitting antennas 108. For example, the transmission antenna 108 that transmits the radar transmission signal a plurality of times may be a transmission antenna near the center in the arrangement of the plurality of transmission antennas 108.

  FIG. 14B shows, as an example of N> Nt, when Nt = 5 and N = 6, in the transmission cycle T, the transmission antennas corresponding to the virtual antennas whose arrangement positions overlap (for example, Tx # 3 and Tx # 4). An example of the transmission timing when the number of transmissions in ()) is three is shown. In FIG. 14B, transmission antenna Tx # 3 is a transmission antenna arranged at the center of transmission antennas Tx # 1 to Tx # 5 (or a transmission antenna other than the transmission antenna farthest from the center of gravity). In other words, Tx # 3 is a transmission antenna that forms a virtual antenna near the center on the virtual antenna arrangement. In the case of FIG. 14B, the transmission timing of Tx # 3 is set twice, and the transmission timing of Tx # 4 is set once. Thereby, the radar apparatus 10 can reduce the side lobe on the angle profile at the time of the direction estimation by the effect of the window function.

(Variation 2 of one embodiment)
In Variation 2, a case will be described in which a signal obtained by beamforming using a plurality of antennas (a plurality of transmitting antennas 108 or a plurality of receiving antennas 202) is treated as a real signal having a phase center different from that of each antenna.

  FIG. 15 shows an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 according to Variation 2 and an arrangement of the virtual reception array.

  In FIG. 15, the number of transmitting antennas 108 is Nt = 3 (for example, Tx # 1, Tx # 2, and Tx # 3), and the number of receiving antennas 202 is Na = 2 (for example, Rx # 1 and Rx # 2). And However, the values of Nt and Na are not limited to the example shown in FIG.

  For example, the antenna elements of the transmitting antenna 108 and the receiving antenna 202 are arranged at an integer multiple of the interval d. In FIG. 15, Tx # 1, Tx # 2, and Tx # 3 are each arranged at an interval of 2d, and Rx # 1 and Rx # 2 are arranged at an interval of 3d. Note that the interval d is about a half wavelength, and for example, d = 0.5λ.

  In variation 2, the radar device 10 forms a beam with two elements Tx # 2 and Tx # 3 by controlling and feeding the phases of Tx # 2 and Tx # 3 in the transmission antenna 108 shown in FIG. (In other words, antenna combining). In FIG. 15, the phase centers of the two elements exist between Tx # 2 and Tx # 3. For example, when power is supplied to Tx # 2 and Tx # 3 with equal power, the phase center of the two elements is the midpoint between Tx # 2 and Tx # 3 as shown in FIG.

  In FIG. 15, the interval 3d between the phase center point of the two elements Tx # 2 and Tx # 3 (for example, the phase center of the combined antenna) and Tx # 1 is the interval between Rx # 1 and Rx # 2. Same as 3d.

  In this case, as illustrated in FIG. 15, in the virtual reception array, a virtual antenna (in other words, a virtual antenna corresponding to antenna synthesis) configured by the combined antenna of Tx # 2 and Tx # 3 and Rx # 1, The virtual antenna VA # 2 constituted by Tx # 1 and Rx # 2 is arranged at the same position so as to overlap. At the position where the two virtual antennas are arranged overlapping, there are two received signals.

  In Variation 2, the radar transmitting unit 100 sets each transmitting antenna so that the transmitting intervals of the Tx # 1 corresponding to the virtual antennas whose placement positions overlap and the composite antennas of Tx # 2 and Tx # 3 are equal. The transmission timing of 108 is switched.

  FIG. 16 shows an example of transmission timing in the antenna arrangement shown in FIG. Note that the transmission timing is not limited to the example illustrated in FIG. 16, and may be set so that the transmission timing of the transmission antenna 108 corresponding to the virtual antenna having the overlapping position is at a constant interval.

  In FIG. 16, the transmission interval (transmission cycle) of each of the transmission antennas 108 of Tx # 1, Tx # 2, and Tx # 3 is T = 4Tr. Further, as shown in FIG. 16, the transmission timing of Tx # 1 and the transmission timing of the combined antenna (Tx # 2 + Tx # 3) of Tx # 2 and Tx # 3 (in other words, Tx # 2 and Tx # 3 At the same time) is T ′ = 2Tr. Therefore, as shown in FIG. 16, the transmission interval T ′ between Tx # 1 and the combined antenna of Tx # 2 and Tx # 3 is 2Tr = T / 2, which is equal.

  In the case of FIG. 16, the radar apparatus 10 receives a reflected wave signal at every transmission cycle T ′ = 2Tr in the virtual antennas whose arrangement positions overlap in FIG. The radar receiving unit 200 performs Doppler analysis in the Doppler analyzing unit 212 using, for example, received signals respectively received by two virtual antennas whose arrangement positions overlap in FIG.

  Thus, the radar apparatus 10 can receive the reflected wave signal at the virtual antenna arranged at the same position at every transmission interval T '. Therefore, for example, in FIG. 16, the radar apparatus 10 can set the sampling interval to T ′ = T / 2 in the virtual antennas arranged at the same position.

For example, as shown in FIG. 16, when the sampling interval is T = 4Tr, the transmission interval of each transmitting antenna 108 is represented by the maximum value of the relative speed v _max = λ / 4T. Here, λ indicates the wavelength of the carrier frequency. On the other hand, as shown in FIG. 16, the sampling interval T ′ = 2Tr = T / 2 in the virtual antenna corresponding to the transmission interval (2Tr) between Tx # 1 and the combined antenna of Tx # 2 and Tx # 3. If the in, represented by the maximum value _{v 'max = λ / 4T'} = 2v max of the relative velocity.

Thereby, in FIG. 15, the maximum value v ' _max (or Doppler frequency range) of the relative speed is expanded to twice the maximum value v _max of the relative speed based on the transmission interval T for each transmitting antenna 108. In other words, the Doppler frequency range (relative speed) in which aliasing does not occur is doubled as compared with the case where the virtual reception arrays do not overlap.

  Therefore, in Variation 2, the radar apparatus 10 does not generate aliasing (in other words, does not generate ambiguity) as compared with the case where virtual antennas do not overlap in the virtual reception array. The Doppler frequency range (maximum relative velocity) And the direction of arrival can be accurately estimated.

  In variation 2, radar transmission signals are simultaneously transmitted from at least two transmission antennas 108 among a plurality (for example, three or more) of transmission antennas 108. Thereby, the arrangement position of the virtual antenna is determined based on the phase center point between the at least two transmission antennas 108. Therefore, for example, as compared with the above-described embodiment, the virtual antennas constituted by the transmission antennas 108 alone do not need to overlap. For example, in FIG. 15, the virtual antennas VA # 1 to VA # 6 configured by a combination of Tx # 1 to Tx # 3, Rx # 1 and Rx # 2 do not overlap each other. By doing so, in Variation 2, the Doppler frequency range (or the maximum value of the relative velocity) can be expanded without reducing the aperture length of the virtual reception array.

  Also, for example, the antenna combination of Tx # 2 and Tx # 3 shown in FIG. 15 is formed by the antenna combination of Tx # 2 and Tx # 3 since the phase center is a combination of antenna elements separated by one wavelength or more. The combined beam has a small main lobe width and is adaptable to a narrow range. For example, Variation 2 may be applied to a scene in which it is desired to detect an object having a high relative speed in a narrow range, such as a high-speed object on a highway.

  Note that, in FIG. 15, the antenna combining (simultaneous transmission) of the plurality of transmitting antennas 108 has been described, but the present invention is not limited to this, and the received signals of a plurality of (for example, three or more) receiving antennas 202 may be combined.

  FIG. 17 shows an example in which received signals of a plurality of receiving antennas 202 are combined.

  In FIG. 17, the number of transmitting antennas 108 is Nt = 2 (for example, Tx # 1 and Tx # 2), and the number of receiving antennas 202 is Na = 3 (for example, Rx # 1, Rx # 2 and Rx # 3). I do. However, the values of Nt and Na are not limited to the example shown in FIG.

  For example, the antenna elements of the transmitting antenna 108 and the receiving antenna 202 are arranged at an integer multiple of the interval d. In FIG. 17, Tx # 1 and Tx # 2 are arranged at an interval of 3d, and Rx # 1, Rx # 2 and Rx # 3 are arranged at an interval of 2d. Note that the interval d is about a half wavelength, and for example, d = 0.5λ.

  In FIG. 17, the radar device 10 combines the received signals of Rx # 1 and Rx # 2. For example, as shown in FIG. 17, the phase center of the two elements Rx # 1 and Rx # 2 is the midpoint between Rx # 1 and Rx # 2.

  Also, as shown in FIG. 17, the interval 3d between the phase center point of the two elements Rx # 1 and Rx # 2 (for example, the phase center of the combined antenna) and Rx # 3 is Tx # 1 and Tx # 2. Is the same as 3d.

  In this case, as shown in FIG. 17, in the virtual reception array, a virtual antenna (in other words, a virtual antenna corresponding to antenna synthesis) configured by a combined antenna of Rx # 1 and Rx # 2 and Tx # 2, The virtual antenna VA # 3 constituted by Tx # 1 and Rx # 3 is overlapped and arranged at the same position. At the position where the two virtual antennas are arranged overlapping, there are two received signals.

  In Variation 2, the radar transmission unit 100 switches the transmission timing of each transmission antenna 108 so that the transmission intervals of Tx # 1 and Tx # 2 corresponding to the virtual antennas whose arrangement positions overlap each other are equal. Further, the radar receiver 200 combines the reflected wave signals received at Rx # 1 and Rx # 2. Thereby, the arrangement position of the virtual antenna is determined based on the phase center point between Rx # 1 and Rx # 2.

  Thus, in FIG. 17, as in FIG. 15, the Doppler frequency range (or the maximum value of the relative velocity) can be expanded without reducing the aperture length of the virtual reception array.

  Here, as the antenna combining process, the process of simultaneously transmitting radar transmission signals from the two transmitting antennas 108 and the process of combining the received signals at the two receiving antennas 202 have been described. More than one transmit antenna 108 or more than two receive antennas 202 may be used.

(Variation 3 of one embodiment)
Each of the transmitting antennas 108 and each of the receiving antennas 202 may be configured by a sub-array antenna.

  FIGS. 18 and 19 show an example in which the same antenna arrangement as the arrangement of the transmitting antenna 108 shown in FIG. 9 and the arrangement of the receiving antenna 202 shown in FIG.

  For example, one system (one antenna element) of the transmission antenna 108 and the reception antenna 202 physically interferes with an adjacent antenna with respect to a point on the plane of the first axis and the second axis shown in FIGS. The configuration may be such that the aperture length is widened to such an extent that the sub-array antenna is not used. Thereby, the beam width is narrowed, and a high antenna gain can be obtained. Further, an array weight may be applied to the sub-array antenna to suppress the side lobe.

  For example, as shown in FIG. 18, one antenna system may be configured with a sub-array antenna having four elements in the second axis direction. When the field of view (FOV: Field of View) of the radar device 10 is wide in the horizontal direction and narrow in the vertical direction, the beam pattern of one system of the transmitting antenna 108 and the receiving antenna 202 is also wide in the horizontal direction. , And a narrow angle in the vertical direction is desirable. Therefore, as shown in FIG. 18, a sub-array antenna configuration arranged in the vertical direction (for example, the second axis direction) is conceivable. Note that instead of the antenna arrangement shown in FIG. 18, a sub-array antenna configuration in which elements are arranged in a horizontal direction (for example, the first axis direction) may be used. As described above, it is desirable that one transmission antenna and one reception antenna are configured by a sub-array antenna that forms a beam pattern suitable for the viewing angle of the radar device 10.

  FIG. 18 illustrates a case where all the antenna elements have the same sub-array antenna configuration, but the present invention is not limited to this. For example, the configuration may be changed for each antenna element within a range that does not interfere with an adjacent antenna.

  For example, as shown in FIG. 19, each element of the transmitting antenna 108 is configured by a sub-array of eight elements, two elements in the first axis direction and four elements in the second axis direction. As shown in FIG. 19, among the receiving antennas 202, Rx # 4, Rx # 6, and Rx # 7 have 24 elements of 3 elements in the first axis direction and 8 elements in the second axis direction. Rx # 1, Rx # 2, Rx # 3, Rx # 5 and Rx # 8 are four-element sub-arrays, one element in the first axis direction and four elements in the second axis direction. Be composed. In the antenna configuration of FIG. 19, for example, the beam pattern of one antenna becomes narrower and the viewing angle (FOV) becomes narrower than the antenna configuration of FIG. 18. Thereby, in the radar apparatus 10 having the antenna configuration illustrated in FIG. 19, the antenna gain in the front direction is improved, and the SNR (Signal to Noise Ratio or S / N ratio) can be improved.

  Further, as shown in FIG. 9, FIG. 10, FIG. 18 or FIG. 19, even if dummy antenna elements are installed for the transmission antenna 108 (antenna element) and the reception antenna 202 (antenna element) which are arranged at unequal intervals. Good. For example, in FIG. 18, a dummy antenna element may be provided in the right region of Rx # 1 or the left region of Rx # 8. By providing the dummy antenna element, an effect of equalizing the influence of electrical characteristics such as radiation, impedance matching, and isolation of the antenna can be obtained.

(Variation 4 of one embodiment)
In Variation 4, with respect to the antenna arrangement of the transmitting antenna 108 and the receiving antenna 202, other arrangement examples other than the arrangement examples 1 and 2 will be described. Note that the antenna arrangement example (for example, the number of antennas or the antenna arrangement position) described below is an example, and is not limited thereto.

  In addition, an interval of one cell shown in FIGS. 20 to 23, 25, and 27 to 30 described later is represented by “d”. However, the distance d may be different between the first axis and the second axis.

(Arrangement example 3: Nt = 6 and Na = 8)
In arrangement example 3, when the number of transmitting antennas 108 is Nt = 6 (for example, Tx # 1 to Tx # 6) and the number of receiving antennas 202 is Na = 8 (for example, Rx # 1 to RX # 8) The antenna arrangement example will be described. In the third arrangement example, one of the transmitting antenna 108 and the receiving antenna 202 is a one-dimensional linear array, and the other is a two-dimensional planar array.

<Arrangement example 3-1>
FIG. 20 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 3-1.

  In FIG. 20, Tx # 1 to Tx # 6 are linearly arranged at an interval d in the first axis direction, for example. Further, in FIG. 20, Rx # 1 to Rx # 4 and Rx # 5 to Rx # 8 are arranged at intervals d in the second axis direction, and a set of Rx # 1 to Rx # 4 and Rx # 5 to Rx # 8 pairs are arranged at an interval of 3d in the first axis direction.

  In this case, as shown in FIG. 20, the virtual reception array arrangement (Nt × Na = 48 virtual antennas) corresponds to the virtual antennas corresponding to Tx # 1 and Tx # 4, and to Tx # 2 and Tx # 5. The virtual antenna and the virtual antennas corresponding to Tx # 3 and Tx # 6 are respectively arranged at four positions in the second axis direction. In FIG. 20, there are two virtual antennas overlapping at each arrangement position (hereinafter, may be referred to as "one overlap").

  As described above, the plurality of virtual antennas corresponding to at least one transmission antenna 108 (for example, Tx # 1 to Tx # 6 in FIG. 20) overlap with the virtual antennas corresponding to other transmission antennas 108 at a plurality of positions. Placed. Thereby, the radar device 10 can improve the quality (for example, SNR) of the received signal by using the received signals received by the virtual antennas at the plurality of arrangement positions.

<Arrangement example 3-2>
FIG. 21 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 3-2.

  FIG. 21 shows that, in the receiving antenna 202, the antenna spacing in the first axis direction is the same as the antenna arrangement of the arrangement example 3-1 (FIG. 20), and Rx # 2, Rx # 4, Rx # 6, This is an antenna arrangement in which the arrangement position of Rx # 8 is shifted to the right by a distance d in the first axis direction. In the antenna arrangement shown in FIG. 21, as in FIG. 20, the virtual antennas corresponding to the respective transmission antennas 108 are overlapped with the virtual antennas corresponding to the other transmission antennas at a plurality of arrangement positions. The quality (for example, SNR) of the received signal can be improved.

<Arrangement example 3-3>
FIG. 22 shows an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 3-3.

  In FIG. 22, the transmitting antenna 108 has Tx # 1 to Rx # 3, and Tx # 4 to Tx # 6, which are arranged at intervals d in the second axis direction, and a set of Tx # 1 to Tx # 3. A set of Tx # 4 to Tx # 6 is arranged at an interval of 4d in the first axis direction. In FIG. 22, Rx # 1 to Rx # 8 are linearly arranged at an interval d in the first axial direction, for example.

  In this case, as shown in FIG. 22, in the virtual receiving array arrangement (Nt × Na = 48 virtual antennas), it corresponds to the virtual antennas corresponding to Tx # 1 and Tx # 4, Tx # 2 and Tx # 5. The virtual antenna and the virtual antennas corresponding to Tx # 3 and Tx # 6 are respectively arranged at four positions in the first axis direction. In FIG. 22, the number of virtual antennas overlapping at each position is two (one overlap).

  Thus, the plurality of virtual antennas corresponding to at least one transmission antenna 108 (for example, Tx # 1 to Tx # 6 in FIG. 22) overlap with the virtual antennas corresponding to other transmission antennas 108 at a plurality of positions. Placed. Thereby, the radar device 10 can improve the quality (for example, SNR) of the received signal by using the received signals received by the virtual antennas at the plurality of arrangement positions.

<Arrangement example 3-4>
FIG. 23 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 3-4.

  FIG. 23 shows that, in the transmission antenna 108, the antenna spacing in the first axial direction is the same as the antenna arrangement of the arrangement example 3-3 (FIG. 22), and the arrangement positions of Tx # 2 and Tx # 5 are This is an antenna arrangement in which the positions of Tx # 3 and Tx # 6 are shifted to the right by an interval d in the one-axis direction and shifted to the right by an interval 2d in the first axis direction. In the antenna arrangement shown in FIG. 23, as in FIG. 22, the virtual antenna corresponding to each transmission antenna 108 is overlapped with the virtual antenna corresponding to another transmission antenna at a plurality of arrangement positions. The quality (for example, SNR) of the received signal can be improved.

  The arrangement examples 3-1 to 3-4 have been described above.

  FIG. 24 shows an example of the transmission timing of each transmission antenna 108 (Tx # 1 to Tx # 6) in arrangement example 3 (see, for example, FIGS. 20 to 23).

  As shown in FIG. 24, the transmission cycle T of each of the transmission antennas 108 from Tx # 1 to Tx # 6 is 6Tr. As shown in FIG. 24, a set of transmission antennas 108 corresponding to virtual antennas arranged at the same position (for example, Tx # 1 and Tx # 4, Tx # 2 and Tx # 5, and Tx # 3 and Tx # 6) Each transmission cycle T 'is 3Tr. In other words, the transmission cycle T ′ = T / 2 of the set of transmission antennas 108 constituting the virtual antenna arranged at the same position.

Therefore, with the antenna arrangement of arrangement example 3, the maximum value v ' _max (or Doppler frequency range) of the relative speed is expanded to twice the maximum value v _max of the relative speed based on the transmission interval T for each transmitting antenna 108. You.

(Arrangement example 4: Nt = 6 and Na = 8)
In the fourth arrangement example, an antenna arrangement example in which the number of transmitting antennas 108 is Nt = 6 (for example, Tx # 1 to Tx # 6) and the number of receiving antennas 202 is Na = 8 will be described. In the arrangement example 4, both the transmitting antenna 108 and the receiving antenna 202 are two-dimensional planar arrays.

  FIG. 25 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 4.

  In FIG. 25, a set of Tx # 2 and Tx # 3 and a set of Tx # 4 and Tx # 5 are arranged at an interval of 2d in the first axis direction. Further, Tx # 3 and Tx # 5 are arranged at an interval d in the first axis direction and at an interval 2d in the second axis direction, respectively, with respect to Tx # 1. Similarly, Tx # 2 and Tx # 4 are arranged at an interval d in the first axis direction and at an interval 2d in the second axis direction, respectively, with respect to Tx # 6. In FIG. 25, two sets of four antenna elements (a set of Rx # 1 to Rx # 4 and a set of Rx # 5 to Rx # 8) arranged at a distance d in the first axis direction are They are arranged at a distance of 2d in the two axial directions.

  In this case, as shown in FIG. 25, in the virtual reception array arrangement (Nt × Na = 48 virtual antennas), Tx # 1 and Tx # 3, Tx # 2 and Tx # 4, Tx # 3 and Tx # 5 , Tx # 4 and Tx # 6, Tx # 1 and Tx # 5, and virtual antennas corresponding to Tx # 2 and Tx # 6, respectively, are arranged at the same position at one time. In addition, virtual antennas respectively corresponding to the set of Tx # 1, Tx # 3 and Tx # 5, and the set of Tx # 2, Tx # 4 and Tx # 6 are arranged twice at the same position in two places. You.

  In FIG. 25, two overlapping virtual receiving arrays are arranged at the center, and one overlapping virtual antenna and a non-overlapping virtual antenna are radially arranged. Therefore, the virtual reception array arrangement shown in FIG. 25 is an arrangement in which the reception power becomes higher as the reception power at the center of the virtual reception array increases. In this way, the distribution becomes spatially like a window function, and the side lobe level in the beam pattern formed by the array is lower than that in a case where similar reception arrays are arranged without overlap, thereby reducing the risk of erroneous detection. . In addition, the signals of the overlapping virtual reception array can be used for arrival direction estimation by performing processing such as addition, averaging, or applying a window function to the spatial power distribution.

  FIG. 26 shows an example of the transmission timing of each transmission antenna 108 (Tx # 1 to Tx # 6) in arrangement example 4 (see, for example, FIG. 25).

  As shown in FIG. 26, the transmission cycle T of each of the transmission antennas 108 from Tx # 1 to Tx # 6 is 6Tr. As shown in FIG. 26, a set of transmission antennas 108 corresponding to virtual antennas arranged twice in the same position (for example, a set of Tx # 1, Tx # 3 and Tx # 5, and Tx # 2, The transmission cycle T ′ for each (set of Tx # 4 and Tx # 6) is 2Tr. In other words, the transmission cycle T '= T / 3 of the set of transmission antennas 108 constituting the virtual antenna arranged at the same position.

Therefore, the maximum value v ' _max (or Doppler frequency range) of the relative speed is expanded to three times the maximum value v _max of the relative speed based on the transmission interval T for each transmitting antenna 108 by the antenna arrangement of FIG. .

  Also, in FIG. 25, the virtual antennas corresponding to the respective transmitting antennas 108 are overlapped with the virtual antennas corresponding to the other transmitting antennas at a plurality of arrangement positions, so that the quality of the received signal in the radar device 10 (for example, SNR) can be improved.

  The antenna arrangement shown in FIG. 26 may be applied instead of the antenna arrangement shown in FIG. FIG. 26 shows an antenna arrangement obtained by rotating the arrangement of the transmitting antenna 108 shown in FIG. 25 by 90 degrees. In this case, as shown in FIG. 26, virtual antennas corresponding to a set of Tx # 1, Tx # 2, Tx # 3, and Tx # 4 are arranged at the same three locations at three times. Thereby, similarly to FIG. 25, the maximum value of the relative speed can be expanded, and the quality (for example, SNR) of the received signal in the radar device 10 can be improved.

  FIG. 28 shows an example of the transmission timing of each transmission antenna 108 (Tx # 1 to Tx # 6) in FIG.

  As shown in FIG. 28, the transmission cycle T of each of the transmission antennas 108 of Tx # 1 to Tx # 6 is 8Tr. Also, as shown in FIG. 28, the transmission cycle for each set of transmission antennas 108 (Tx # 1, Tx # 2, Tx # 3, and Tx # 4) corresponding to virtual antennas arranged at the same position three times in an overlapped manner T 'is 2Tr. In addition, the transmission cycle T 'for each of the transmission antennas Tx # 5 and Tx # 6 corresponding to the virtual array that is duplicated twice is 2Tr.

When the radar device 10 performs speed estimation using the virtual reception array having these transmission periods (T '= 2Tr), if the conventional transmission period Torg = 6Tr, the transmission period T' = Torg / 3. Therefore, v ′ _max (or Doppler frequency range) is expanded to three times the maximum value v _max of the relative speed based on the transmission interval Torg for each transmitting antenna 108.

  Further, a configuration in which the radar apparatus 10 performs speed estimation using the signal of the virtual reception array with the transmission cycle T ′ = 4Tr may be considered. As a result, the radar apparatus 10 transmits a signal of a set of transmission antennas (a set of Tx # 1 and Tx # 2 and a set of Tx # 3 and Tx # 4) corresponding to the virtual reception array that is one overlap in FIG. , Tx # 5 and Tx # 6, and the signal of the virtual reception array of three overlapping times may be added to perform the speed estimation processing and the CFAR processing.

In the case where the radar apparatus 10 performs speed estimation using the virtual reception array having these transmission periods (T '= 4Tr), if the conventional transmission period Torg = 6Tr, the transmission period T' = 2T / 3. Therefore, v ′ _max (or Doppler frequency range) is expanded to 1.5 times the maximum value v _max of the relative speed based on the transmission interval Torg for each transmitting antenna 108. Although the maximum speed that can be obtained is smaller than in the case of the transmission period T ′ = 4Tr, since the number of virtual reception array signals used for speed estimation is large, the quality (for example, SNR) of the reception signal used for CFAR processing can be improved. it can.

  In the configuration shown in FIGS. 27 and 28, the radar device 10 can select the above-described reception processing. For example, the radar apparatus 10 performs a process using a received signal having a transmission period T ′ = 2Tr when detecting a reflected object having a large reflection intensity and a large relative speed, and performs a transmission period T ′ when the reflection intensity is lower than the above. Processing using a received signal of = 4Tr can also be performed.

Also, not all of the transmitting antennas 108 need to be multiplexed. For example, the radar apparatus 10 continuously transmits radar transmission signals using only Tx # 1, Tx # 2, Tx # 3, and Tx # 4 corresponding to overlapping virtual reception antennas among the transmission antennas illustrated in FIG. Send. Thereby, the radar apparatus 10 can perform speed estimation using the signal of the virtual reception array with the transmission cycle T ′ = Tr. Assuming that the conventional transmission cycle Torg = 6Tr, the transmission cycle T ′ = Torg / 6. Therefore, v ′ _max (or Doppler frequency range) is expanded to six times the maximum value v _max of the relative speed based on the transmission interval Torg for each transmitting antenna 108. As described above, the radar device 10 may adopt a configuration capable of responding at a higher speed. For example, the radar device 10 may have a configuration that can respond at higher speed and a configuration that can improve the accuracy of arrival direction estimation by switching the transmission timing pattern of the transmission antenna depending on the detection target. In addition, although the present arrangement example of the present embodiment in which a large number of virtual receiving antennas overlap is described as an example, the present invention is not limited to this and may be applied.

(Arrangement example 5: Nt = 3 and Na = 4)
In Arrangement Example 5, an antenna arrangement example in which the number of transmitting antennas 108 is Nt = 3 (for example, Tx # 1 to Tx # 3) and the number of receiving antennas 202 is Na = 4 will be described. In the arrangement example 5, the transmitting antenna 108 is a one-dimensional linear array, and the receiving antenna 202 is a two-dimensional planar array.

<Arrangement example 5-1>
FIG. 29 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 5-1.

  In FIG. 29, Tx # 1 to Tx # 3 are linearly arranged at an interval d in the first axis direction, for example. Further, the reception antenna 202 has, for example, two sets of two elements (a set of Rx # 1 and Rx # 2 and a set of Rx # 3 and Rx # 4) arranged at an interval d in the second axis direction, and In the axial direction, the two sets of elements are arranged at a distance of 2d.

  In this case, as shown in FIG. 29, in the virtual receiving array arrangement (Nt × Na = 12 virtual antennas), the virtual antennas corresponding to Tx # 1 and Tx # 3 are respectively located at two locations in the second axis direction. They are arranged overlapping (one overlap).

  Thereby, in FIG. 29, the radar apparatus 10 can improve the quality (for example, SNR) of the received signal by using the received signals received by the virtual antennas at the plurality of arrangement positions.

<Arrangement example 5-2>
FIG. 30 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 5-2.

  FIG. 30 shows that, in the receiving antenna 202, the antenna spacing (2d) in the first axis direction is the same as the antenna arrangement of the arrangement example 5-1 (FIG. 29), and the arrangement of Rx # 2 and Rx # 4 This is an antenna arrangement in which the position is shifted to the right by a distance d in the first axis direction. In the antenna arrangement shown in FIG. 30, as in FIG. 29, the virtual antenna corresponding to each transmission antenna 108 is overlapped with the virtual antenna corresponding to another transmission antenna at a plurality of arrangement positions. The quality (for example, SNR) of the received signal can be improved.

<Arrangement example 5-3>
FIG. 31 illustrates an example of an antenna arrangement of the transmission antenna 108 and the reception antenna 202 and an arrangement of the virtual reception array according to the arrangement example 5-3.

In FIG. 31, the total number Nt of the transmission antennas 108 is three, which are indicated by Tx # 1 to Tx # 3, respectively. Transmission antenna Tx # 1 to TX # 3 are equally spaced apart about the first axis direction at an interval of d _H. Here, the basic interval d _H in the first axial direction is, for example, d _H = 0.5λ. The total number Na of the receiving antennas 202 is four, which are indicated by Rx # 1 to Rx # 4, respectively. Receive antennas Rx # 1~Rx # 4 is disposed in a first axial direction at an interval of [3,2,3] × d _H.

  As shown in FIG. 31, at the position of the virtual antenna VA # 6, a virtual antenna configured by a transmission antenna Tx # 3 and a reception antenna Rx # 2, a transmission antenna Tx # 1 and a reception antenna Rx # 3, And a virtual antenna constituted by the same.

  FIG. 32 shows an example of the transmission timing of each transmission antenna 108 (Tx # 1 to Tx # 3) in FIG. The transmission cycle T of each of the transmission antennas 108 from Tx # 1 to Tx # 3 is 4Tr. As shown in FIG. 32, the transmission period T ′ for each pair (Tx # 1, Tx # 3) of the transmission antennas 108 corresponding to the virtual antennas that are arranged once at the same position is 2Tr. Further, as shown in FIG. 32, the transmission cycle T ′ of the transmission antenna Tx # 2 is also 2Tr. Therefore, the radar device 10 may perform the speed estimation processing and the CFAR processing by adding the virtual reception array based on Tx # 2 to the signal of the virtual reception array of one overlap.

When speed estimation is performed using the virtual reception array having these transmission periods (T ′ = 2Tr), if the conventional transmission period Torg = 3Tr, the transmission period T ′ = 2T / 3. Therefore, v ′ _max (or Doppler frequency range) is expanded to 1.5 times the maximum value v _max of the relative speed based on the transmission interval Torg for each transmitting antenna 108.

  This transmission method also has an advantage in SNR. Normally, as shown in FIG. 32, from Tx # 2 having no overlap with the virtual antenna (if Nt = 3, N = 3), only one radar transmission signal is transmitted out of N transmission times, so that the entire The number of transmissions is Nc. However, as described above, the radar transmission signal is transmitted from Tx # 2 that does not overlap the virtual antenna twice each out of the number of transmissions N, so that the total number of transmissions is 2Nc. In addition, since these transmissions are all transmitted at intervals of 2Tr, the in-phase addition of the received signal can be performed by FFT, and an improvement in SNR can be expected.

(Variation 5 of one embodiment)
The configuration of the radar device according to an aspect of the present disclosure is not limited to the configuration illustrated in FIG. For example, the configuration of the radar device 10a shown in FIG. 33 may be used. Note that, in FIG. 33, the configuration of the radar receiving unit 200 is the same as that in FIG.

  In the radar device 10 shown in FIG. 1, the output from the radar transmission signal generation unit 101 is selectively switched to any one of the plurality of transmission radio units 107 by the transmission switching unit 106 in the radar transmission unit 100. On the other hand, in the radar apparatus 10a shown in FIG. 33, in the radar transmission section 100a, the output (radar transmission signal) from the radar transmission signal generation section 101 is subjected to transmission radio processing by the transmission radio section 107a, and transmission switching is performed. The output of the transmission radio section 107a is selectively switched to any one of the plurality of transmission antennas 108 by the section 106a.

  With the configuration of the radar device 10a shown in FIG. 33, the same effect as in the above embodiment can be obtained.

(Variation 6 of one embodiment)
In the above-described embodiment, a case has been described where the radar transmitting section 100 uses a pulse compression radar that transmits a pulse train by performing phase modulation or amplitude modulation, but the modulation method is not limited to this. For example, the present disclosure is also applicable to a radar system using a frequency-modulated pulse wave such as a chirp pulse.

  FIG. 34 shows an example of a configuration diagram of a radar device 10b when a radar system using chirped pulses (for example, fast chirp modulation) is applied. 34, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  First, transmission processing in the radar transmission unit 100b will be described.

  In the radar transmission unit 100b, the radar transmission signal generation unit 401 has a modulation signal generation unit 402 and a VCO (Voltage Controlled Oscillator) 403.

  The modulation signal generation unit 402 periodically generates a sawtooth modulation signal, for example, as shown in FIG. Here, the radar transmission cycle is assumed to be Tr.

  VCO 403 outputs a frequency modulation signal (in other words, a frequency chirp signal) to transmission radio section 107 based on the radar transmission signal output from modulation signal generation section 402. The frequency modulated signal is amplified in transmission radio section 107 and radiated into space from transmission antenna 108 switched in transmission switching section 106. For example, in each of the first to Nt-th transmission antennas 108, a radar transmission signal is transmitted at a transmission interval of Np (= Nt × Tr) cycles.

  The directional coupling unit 404 extracts a part of the frequency modulation signal and outputs the signal to each reception radio unit 501 (mixer unit 502) of the radar reception unit 200b.

  Next, a reception process in the radar receiver 200b will be described.

  The reception radio section 501 of the radar reception section 200b mixes the received reflected wave signal with a frequency modulation signal (signal input from the directional coupling section 404), which is a transmission signal, in the mixer section 502, and outputs the LPF 503. Let it pass. Thus, a beat signal having a frequency corresponding to the delay time of the reflected wave signal is extracted. For example, as shown in FIG. 35, the difference frequency between the frequency of the transmission signal (transmission frequency modulation wave) and the frequency of the reception signal (reception frequency modulation wave) is obtained as the beat frequency.

  The signal output from LPF 503 is converted to discrete sample data by A / D conversion section 208b in signal processing section 207b.

The R-FFT section 504 performs an FFT process on N _data discrete sample data obtained in a predetermined time range (range gate) for each transmission cycle Tr. Thus, the signal processing unit 207b outputs a frequency spectrum in which a peak appears at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). At the time of the FFT processing, the R-FFT unit 504 may multiply by a window function coefficient such as a Han window or a Hamming window. By using the window function coefficient, side lobes generated around the beat frequency peak can be suppressed.

Here, the beat frequency spectrum response output from the R-FFT unit 504 in the z-th signal processing unit 207b obtained by the M-th chirp pulse transmission is represented by AC_RFT _z (fb, M). Here, fb is an index number (bin number) of the FFT, and fb = 0,..., N _data / 2. The smaller the frequency index fb, the shorter the delay time of the reflected wave signal (in other words, the shorter the distance from the target), the beat frequency.

  The output switching unit 211 in the z-th signal processing unit 207b outputs the output of the R-FFT unit 504 for each radar transmission cycle Tr based on the switching control signal input from the switching control unit 105, as in the above embodiment. Is selectively switched to one of the Nt Doppler analyzers 212 and output.

Hereinafter, as an example, the switching control signal in the M-th radar transmission cycle Tr [M] is represented by Nt bit information [bit ₁ (M), bit ₂ (M),..., Bit _Nt (M)]. For example, in the switching control signal of the M-th radar transmission cycle Tr [M], when the ND-th bit bit _ND (M) (where ND = 1 to Nt) is “1”, the output is performed. The switching unit 211 selects the ND-th Doppler analysis unit 212 (in other words, turns ON). On the other hand, when the ND-th bit bit _ND (M) is “0” in the switching control signal of the M-th radar transmission cycle Tr [M], the output switching unit 211 outputs the ND-th Doppler analysis unit. 212 is not selected (in other words, OFF). The output switching unit 211 outputs a signal input from the R-FFT unit 504 to the selected Doppler analysis unit 212.

  As described above, the selection of each Doppler analysis unit 212 is sequentially turned ON at Np (= Nt × Tr) cycles. The switching control signal repeats the above content Nc times. Also, as in the above-described embodiment, in the virtual reception array, the selection of the Doppler analysis unit 212 corresponding to the transmission antenna 108 corresponding to the virtual antenna overlappingly arranged at the same position (in other words, the transmission timing of the transmission antenna 108) ) Are set at equal intervals in the transmission cycle of each transmission antenna 108.

Note that the transmission start time of the transmission signal in each transmission radio section 107 does not have to be synchronized with the cycle Tr. For example, each transmission radio section 107 may start transmission of a radar transmission signal by providing different transmission delays Δ ₁ , Δ ₂ ,..., _ΔNt at the transmission start time.

  The z-th (z = 1,..., Na) -th signal processing unit 207b includes Nt Doppler analysis units 212.

  The Doppler analysis unit 212 performs Doppler analysis on the output from the output switching unit 211 for each beat frequency index fb.

  For example, when Nc is a power of 2, fast Fourier transform (FFT) processing can be applied in Doppler analysis.

For example, of the w-th output of the ND-th Doppler analyzer 212 of the z-th signal processor 207b, the output of the virtual receiving array to be superimposed is the Doppler at the beat frequency index fb as shown in the following equation. Doppler frequency response FT_CI _z ^(ND) of the frequency index _{f s (fb, f s,} w) indicates a. Note that ND = 1 to Nt, and w is an integer of 1 or more. _Nva indicates the number of antennas corresponding to the virtual reception array to be superimposed, and N indicates the number of transmissions in one cycle. Further, j is an imaginary unit, and z = 1 to Na.

On the other hand, for example, among the w-th output in the ND-th Doppler analyzer 212 of the z-th signal processing unit 207b, the output in the non-superimposed virtual reception array other than the superimposed virtual reception array is expressed by the following equation. shown as shows Doppler frequency response FT_CI _z Doppler frequency index f _u in the beat frequency index ^{fb (ND) (fb, f} u, w). Note that ND = 1 to Nt, ND = 1 to Nt, and w is an integer of 1 or more. Further, j is an imaginary unit, and z = 1 to Na.

  The processing of the signal correction unit 213, the CFAR unit 213, and the direction estimation unit 214 after the signal processing unit 207b is an operation in which the discrete time k described in the above embodiment is replaced with the beat frequency index fb, and therefore a detailed description will be given. Omitted.

  With the above-described configuration and operation, the same effects as those of the above embodiment can be obtained in this variation. In a variation of the embodiment described below, a frequency chirp signal can be similarly applied as a radar transmission signal, and the same effect as in the case of using an encoded pulse signal can be obtained.

The above-mentioned beat frequency index fb may be converted into distance information and output. To convert the beat frequency index fb into distance information R (fb), the following equation may be used. Here, Bw represents the frequency modulation band width of the frequency chirp signals generated by frequency modulation, C ₀ denotes the speed of light.

  Hereinabove, one embodiment according to the present disclosure has been described.

[Other embodiments]
(1) In the radar device 10 shown in FIG. 1, the radar transmitting unit 100 and the radar receiving unit 200 may be individually arranged at physically separated locations. Further, in the radar receiving section 200 shown in FIG. 1, the direction estimating section 214 and the other components may be individually arranged at physically separated places.

  (2) Although not shown, the radar device 10 includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). Have. In this case, the function of each unit described above is realized by the CPU executing the control program. However, the hardware configuration of the radar device 10 is not limited to such an example. For example, each functional unit of the radar device 10 may be realized as an IC (Integrated Circuit) which is an integrated circuit. Each functional unit may be individually formed into one chip, or may be formed into one chip so as to include a part or the whole thereof.

  Although various embodiments have been described with reference to the drawings, it is needless to say that the present disclosure is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the claims, and these naturally belong to the technical scope of the present disclosure. I understand. Further, each component in the above embodiment may be arbitrarily combined without departing from the spirit of the disclosure.

  In each of the above embodiments, the present disclosure has been described with respect to an example in which the present disclosure is configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

  Further, each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiment and include an input terminal and an output terminal. These may be individually integrated into one chip, or may be integrated into one chip so as to include some or all of them. Although an LSI is used here, it may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI, and may be realized using a dedicated circuit or a general-purpose processor. After manufacturing the LSI, a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring connection or setting of circuit cells inside the LSI may be used.

  Furthermore, if an integrated circuit technology that replaces the LSI appears due to the advancement of the semiconductor technology or another technology derived therefrom, the functional blocks may be integrated using the technology. Application of biotechnology, etc. is possible.

<Summary of this disclosure>
A radar device according to an embodiment of the present disclosure includes a plurality of transmission antennas, and a transmission circuit that transmits a transmission signal using the plurality of transmission antennas, and is configured based on a plurality of reception antennas and the plurality of transmission antennas. At least two of the virtual receiving arrays including a plurality of virtual antennas have the same arrangement position, and are sequentially transmitted from transmission antennas corresponding to the at least two virtual antennas among the plurality of transmission antennas. The transmission intervals of the transmission signal are equal.

  In the radar device according to the present disclosure, the transmission circuit transmits the transmission signal in a predetermined transmission pattern using the plurality of antennas.

  In the radar device according to an embodiment of the present disclosure, in the transmission pattern, the plurality of antennas include a transmission antenna that transmits the transmission signal a plurality of times.

  In the radar device according to an embodiment of the present disclosure, transmission antennas that transmit the transmission signal a plurality of times in the transmission pattern are transmission antennas other than the transmission antenna farthest from the center of gravity in the antenna arrangement of the transmission antennas.

  In the radar device according to the present disclosure, the plurality of virtual antennas corresponding to at least one of the plurality of transmission antennas are arranged so as to overlap with the virtual antennas corresponding to other transmission antennas at a plurality of arrangement positions. You.

  In the radar device according to the present disclosure, the transmission circuit continuously transmits the transmission signal from a transmission antenna corresponding to the at least two virtual antennas among the plurality of transmission antennas.

  In the radar device according to the present disclosure, the transmission signals are simultaneously transmitted from at least two transmission antennas among three or more transmission antennas, and an arrangement position of the at least two virtual antennas is a phase center between the at least two transmission antennas. Determined based on points.

  The radar device according to the present disclosure further includes a receiving circuit that receives a reflected wave signal in which the transmission signal is reflected on the target by using three or more receiving antennas, and the receiving circuit includes the three or more receiving antennas. The reflected wave signals received by at least two of the receiving antennas are combined, and an arrangement position of the at least two virtual antennas is determined based on a phase center point between the at least two receiving antennas.

  In the radar device according to the present disclosure, the plurality of transmitting antennas are two-dimensionally arranged.

  The present disclosure is suitable as a radar device that detects a wide angle range.

10, 10a, 10b Radar device 100, 100a, 100b Radar transmitter 101, 101a, 401 Radar transmission signal generator 102 Code generator 103 Modulator 104, 503 LPF
105 Switching control section 106, 106a Transmission switching section 107, 107a Transmission radio section 108 Transmission antenna 111 Code storage section 112 DA conversion section 200, 200b Radar reception section 201 Antenna system processing section 202 Receiving antenna 203, 501 Reception radio section 204 Amplifier 205 Frequency converter 206 Quadrature detector 207, 207b Signal processing unit 208, 208b, 209 AD conversion unit 210 Correlation calculation unit 211 Output switching unit 212 Doppler analysis unit 213 CFAR unit 214 Direction estimation unit 300 Reference signal generation unit 402 Modulation signal generation unit 403 VCO
404 Directional coupling unit 502 Mixer unit 504 R-FFT unit

Claims (9)

Multiple transmit antennas,
A transmission circuit that transmits a transmission signal using the plurality of transmission antennas,
With
Among the virtual receiving array including a plurality of receiving antennas and a plurality of virtual antennas configured based on the plurality of transmitting antennas, at least two of the virtual antennas are arranged at the same position,
Among the plurality of transmission antennas, transmission intervals of the transmission signals sequentially transmitted from transmission antennas corresponding to the at least two virtual antennas are equal intervals,
Radar equipment. The transmission circuit transmits the transmission signal in a predetermined transmission pattern using the plurality of antennas,
The radar device according to claim 1. In the transmission pattern, the plurality of antennas include a transmission antenna that transmits the transmission signal a plurality of times,
The radar device according to claim 2. In the transmission pattern, the transmission antenna that transmits the transmission signal a plurality of times is a transmission antenna other than the transmission antenna farthest from the center of gravity in the antenna arrangement of the plurality of transmission antennas,
The radar device according to claim 3. The plurality of virtual antennas corresponding to at least one transmission antenna among the plurality of transmission antennas are arranged overlapping with the virtual antennas corresponding to other transmission antennas at a plurality of arrangement positions,
The radar device according to claim 1. The transmission circuit, among the plurality of transmission antennas, from the transmission antenna corresponding to the at least two virtual antennas, to continuously transmit the transmission signal,
The radar device according to claim 1. The transmission signals are simultaneously transmitted from at least two transmission antennas among three or more transmission antennas,
An arrangement position of the at least two virtual antennas is determined based on a phase center point between the at least two transmission antennas,
The radar device according to claim 1. A reception circuit that receives a reflected wave signal in which the transmission signal is reflected on the target, using three or more reception antennas,
The receiving circuit combines the reflected wave signals received by at least two receiving antennas among the three or more receiving antennas,
An arrangement position of the at least two virtual antennas is determined based on a phase center point between the at least two reception antennas,
The radar device according to claim 1. The plurality of transmitting antennas are two-dimensionally arranged,
The radar device according to claim 1.

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