JP2993779B2 - FM-CW radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transmitting a signal which is frequency-modulated (FM-modulated) by a modulated wave having a predetermined repetition frequency, and detects a frequency of a beat wave between a reflected wave from the target and a locally transmitted wave. FM-CW radar device (frequency-modulated continuous-wave radar device) for detecting the distance to the target and the relative speed between the target and the observer, and is particularly suitable for use when a vehicle avoids collision with an obstacle on a road. The present invention relates to an FM-CW radar device.

[0002]

2. Description of the Related Art An FM-CW radar device is a radar device used for detecting the position and relative speed of a target (obstacle) and avoiding collision with the target. It is relatively small and can be realized at low cost. The principle of such an FM-CW radar device is as follows. That is, the carrier wave is FM-modulated by the output from the oscillator and transmitted. The FM-modulated wave is used as a local oscillation wave, and the beat wave between the reflected wave from the target and the local oscillation wave is taken and included in the beat wave frequency. Distance frequency depending on the distance
The position and speed of the target are detected by measuring the speed frequency depending on the number and the speed using a signal processor.

In this case, since the reflected wave from the target is subjected to a delay due to the distance to the target and a Doppler shift due to a relative speed with respect to the target, the position and speed of the transmitted wave are beat by performing FM modulation. It can be detected from the frequency of the wave. Then, the observed since the frequency of the beat wave is equal to the absolute value of the sum and difference of the distance frequency and speed frequency to be detected, by performing such as addition and subtraction to the frequency of the beat wave, the above distance frequencies and speed frequency Seeking.

[0004]

However, in such a conventional FM-CW radar apparatus, the frequency of the beat wave is added or subtracted to obtain the distance frequency and the velocity frequency. In the case of, there is a problem that accurate speed and distance of each target can be detected only in a limited case.

[0005] The present invention has been made in view of the above-mentioned problems, and uses a low-cost method even when there are a plurality of targets.
An object of the present invention is to provide an FM-CW radar device capable of detecting an accurate speed and distance of each target.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. In FIG. 1, reference numeral 1 denotes a frequency modulation wave generation circuit, 1A denotes an RF signal generation circuit, and the frequency modulation wave generation circuit 1 Which generates a frequency modulated wave of
The signal generation circuit 1A performs frequency modulation on a transmission signal.

In this case, it is preferable to use a triangular wave as the repetitive frequency modulation wave. In this frequency modulation, it is preferable that the frequency be modulated at a repetition frequency that is at least twice as high as a speed frequency (detection target speed frequency) that depends on the speed of the beat wave described later.

Further, a distance frequency ( distance frequency to be detected) that depends on the distance in the frequency of the beat wave is higher than twice the repetition frequency of the frequency modulation wave, and the velocity frequency ( in the frequency of the beat wave ) Speed frequency to be detected)
As but lower than 1/2 times the repetition frequency of the frequency-modulated wave, the repetition frequency and modulation of the frequency-modulated wave
At least one of the widths may be set.

Reference numeral 2 denotes a directional coupler.
Transmits the signal modulated by the repetition frequency modulation wave from the frequency modulation wave generation circuit 1 to the transmission antenna 3,
It is extracted as a local oscillation wave to the mixer 6 side. 3
Represents a signal modulated by a repetitive frequency modulation wave from the frequency modulation wave generation circuit 1 into a plurality of targets 4-1 to 4-M
(M is an integer of 2 or more) .

The above-mentioned frequency modulated wave generating circuit 1, RF signal
Generation circuit 1A, directional coupler 2, and transmission antenna 3
The detection target frequency having the detection target distance information is detected.
Higher than the detection target speed frequency having the output target speed information
Transmits a frequency-modulated signal set to a frequency
Frequency modulation signal transmitting means. Further
To, 5 is a receiving antenna for receiving a reflected wave from the target 4-i (i = 1~M) .

Reference numeral 6 denotes a mixer. The mixer 6 mixes the reflected wave from the receiving antenna 5 and the local oscillation wave from the directional coupler 2, and mixes the reflected wave from each target 4-i with the local oscillation. It outputs a beat wave with a wave. Reference numeral 7 denotes an A / D converter, which converts the analog beat wave signal from the mixer 6 into a digital signal.

Reference numeral 8 denotes a window processing circuit which performs digitized window processing on the received beat wave. 9 twice discrete Fourier transform circuit, the two discrete Fourier transform circuit 9, for those subjected to digitized window processing on the received beat wave in the window processing circuit 8, two discrete Fourier transform, i.e., two stages Is applied to detect the distance to each target 4-i and the relative velocity between each target 4-i and the observer. Note that
In the description, the first discrete Fourier transform
Each of the first and second stages of the Fourier transform
What is called the first (first) and second Fourier transform
You.

[0013] Incidentally, the detection target distance frequencies higher than twice the repetition frequency of the frequency-modulated wave, so that the detected speed frequency lower than 1/2 times the repetition frequency of the frequency-modulated wave, frequency modulation wave Repetition frequency and variation
If at least one of the key widths has been set, the distance frequency is obtained by the first discrete Fourier transform, and this distance frequency
Results of multiple discrete Fourier transforms of wave numbers
For time series data for each distance frequency obtained as
By obtaining the velocity frequency by performing the second discrete Fourier transform , the distance to the plurality of targets and the relative velocity between the plurality of targets and the observer are detected.

It is also possible to take in data to be subjected to discrete Fourier transform in the first half of the repetition period of the frequency modulation wave, and to perform discrete Fourier transformation in the second half of the repetition period of the frequency modulation wave. The above receiving antenna 5, mixer
6, A / D converter 7, window processing circuit 8, and twice
In the discrete Fourier transform circuit 9, the frequency modulation signal transmitting means
Received beat wave caused by the frequency modulation signal sent from the
By performing the discrete Fourier transform twice, multiple targets
Detect distance and relative velocity between multiple targets and observer
That is, the detecting means is configured.

[0015]

In the above-described FM-CW radar apparatus of the present invention, a repetition frequency modulated wave from the frequency modulation wave generation circuit 1 through the RF signal generation circuit 1R ( this repetition frequency modulation wave).
Means that the distance frequency to be detected is higher than the speed frequency to be detected
Frequency modulated signal set to
A signal modulated by a triangular wave is transmitted from the transmitting antenna 3 and a beat wave of a reflected wave from each target 4-i received by the receiving antenna 5 and a locally transmitted wave from the directional coupler 2. Is obtained by the mixer 6, and this beat wave is
The signal is digitized by the / D converter 7, subjected to the window processing by the window processing circuit 8, and then subjected to the discrete Fourier transform twice by the discrete Fourier transform circuit 9, thereby obtaining a plurality of targets 4-i. Distance and multiple targets 4-
The relative speed between i and the observer is detected.

[0016] At this time, 2 times higher than the repetition frequency of the detection target distance frequencies frequency modulated wave, so that the detected speed frequency lower than half the repetition frequency of the frequency modulated wave, the frequency Modulation wave repetition frequency
And when that has been set at least one of the modulation width determines the distance frequencies in the first discrete Fourier transform, this
Multiple discrete Fourier transforms
Time series data for each distance frequency
To, by determining the speed frequency by performing a second discrete Fourier transform to detect the relative velocity between the distance and a plurality of target and the observer to a plurality of targets.

Further, data to be subjected to discrete Fourier transform is fetched in the first half of the repetition cycle of the frequency modulation wave, and discrete Fourier transform is performed in the second half of the repetition cycle of the frequency modulation wave.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of the present invention. The FM-CW radar apparatus shown in FIG. 2 includes a triangular wave generator (triangular wave oscillator) 10, an RF signal generating circuit 11, a directional coupler 12, a transmitting antenna. 13, reception antenna 15, mixer 16, A / D converter 17, window processing circuit 1
It comprises an eight or two discrete Fourier transform circuit 19 and a synchronizing signal generating circuit 20.

Here, the triangular wave generator 10 generates a triangular wave, and the RF signal generating circuit 11 generates a signal frequency-modulated (FM modulated) by the triangular wave. In this case, a triangular wave is used as the repeated FM modulation wave. In other words, in this case, the direction in which the frequency increases with respect to the time axis using a triangular wave (ascending gradient)
Then, FM modulation in two directions of decreasing (downward gradient) is repeated.

At the time of this FM modulation, a velocity frequency f _d (detection) which depends on a velocity in the frequency of a beat wave described later.
Than out target speed frequency), least also performs frequency modulation at a high repetition frequency twice or more. Furthermore, the distance frequency f _r (detection pairs depends on the distance in the frequency f _b of the beat wave
The repetition frequency of the triangular wave , the modulation width, and the like are set so that the target distance frequency is higher than twice the repetition frequency of the triangular wave.

That is, detection having distance information to be detected
Detection target speed whose target distance frequency has detection target speed information
Frequency modulation wave so that the frequency becomes higher than the
Repetition frequency, modulation width, etc. are set as parameters
It is being done. The directional coupler 12 extracts the RF signal frequency-modulated by the triangular wave to the transmission antenna 13 and the mixer 16 as a local oscillation wave.

The transmitting antenna 13 is an RF signal generating circuit 1
Repeated FM modulation wave from 1 to multiple targets (obstacles)
14-1 to 14-M also (M is an integer of 2 or more) is sent to the
Than, the receiving antenna 15, each target 14-i (i = 1~
M) to receive the reflected wave. Mixer 16
Represents the reflected wave from the receiving antenna 15 and the directional coupler 1
2 is mixed with the local oscillated wave from the target 14-i to output a beat wave of the reflected wave from each target 14-i and the locally transmitted wave.

The A / D converter 17 converts the analog beat wave signal from the mixer 16 into a digital signal.
The window processing circuit 18 performs a window process (a Hanning window shown in FIG. 5 and a triangular window shown in FIG. 7 are used for the window process).

The two-time discrete Fourier transform circuit 19 performs a two-time discrete Fourier transform on the digitalized window processing of the received beat wave by the window processing circuit 18 to obtain the distance to the target 14-i. And the relative velocity between the target 14-i and the observer is detected. For this purpose, the two-time discrete Fourier transform circuit 19 is used.
Is a Fourier transform processing circuit (FFT processing circuit) 19-
1, a memory 19-2 and a data control circuit 19-3.

Here, the FFT processing circuit 19-1 performs a Fourier transform process, and a dedicated DSP is used. The memory 19-2 stores processed data (for example, the result of the first discrete Fourier transform). The data control circuit 19-3 controls the exchange of data between the FFT processing circuit 19-1 and the memory 19-2.

In this case, the beat wave frequency f _b
Higher than twice the distance frequency f _r is the repetition frequency of the FM modulated signal which depends on the distance in the speed frequency f _d which depends on the speed in the frequency f _b of the beat wave of the repetition frequency of the FM modulated signal 1 / Since the repetition frequency and the modulation width of the FM modulated wave are set so as to be lower than twice, the distance frequency _fr is obtained by the first discrete Fourier transform, and this distance is calculated.
The result of performing the discrete Fourier transform for frequency several times
Time series data for each distance frequency obtained as a result.
And, by determining the speed frequency f _d with the second discrete Fourier transform, it is performed to detect the relative velocity between the distance and a plurality of targets 14-i and the observer to a plurality of targets 14-i.

Further, in the first half of the repetition period of the FM modulation wave, data to be subjected to discrete Fourier transform is fetched,
In the latter half of the repetition period of the M-modulated wave, discrete Fourier transform is performed (see FIG. 12). The synchronization signal generation circuit 20 includes an RF signal generation circuit 11, an A / D converter 17,
Window processing circuit 18, twice discrete Fourier transform circuit 1
9 for generating a synchronizing signal.

Next, the principle of the FM-CW radar device when a triangular wave is used as a modulation wave will be described with reference to FIGS. First, a transmission wave that has been subjected to FM modulation is reflected by a target and then received by a reception antenna 15 to become a reception wave. The frequency of the received wave is shifted from the frequency of the transmitted wave by the delay due to the distance to the target and the Doppler shift due to the relative speed between the target and the observer. The received wave and the local wave are mixed by mixer 1
When mixing at 6, the shifted frequency component (beat wave)
Is detected.

That is, the order of the modulated local oscillation signal
The phase fluctuates every cycle T of frequency modulation. target
If there is no relative speed between the radar and
The phase of the reflected signal fluctuates in the same cycle. Station
The phase of the local oscillation signal and the beat signal of the received signal are also the same.
Periodically fluctuates with the period of the modulated triangular wave. This is the distance frequency
Inverts the sign while the absolute value is constant every half cycle of the triangular wave
That's because.

On the other hand, the velocity frequency is the Doppler shift.
Modulation width (maximum frequency modulation width,
That is, the maximum frequency deviation) ΔΩ is smaller than the center frequency f _0.
If it is sufficiently small, it is constant regardless of the modulation signal. Sand
If there is a relative speed between the target and the radar,
The phase of the reflected signal is the speed frequency
Shifts by the amount corresponding to
The phase of the beat signal also varies with the speed
It shifts by an amount corresponding to the number.

Further, the distance frequency f
It describes a method for separating a _r a speed frequency f _d. If you FM modulated by the triangular wave, the distance frequency f _r and the speed frequency f _d is expressed by the following equation, the distance frequency f _r is dependent on the period T and the modulation width of the modulation wave (the maximum frequency shift) [Delta] [omega , The speed frequency f _d does not depend on the period T of the modulated wave and the modulation width ΔΩ.

F _r = (4ΔΩT / c) R f _d = (2f ₀ / c) v where c is the speed of light, R is the distance to an obstacle (target), f
₀ is a transmission center frequency, and v is a relative speed with respect to an obstacle (target). From the above equation, the range of the distance R to be detected and the detection
If you know the range of relative velocity v you want to emit,
By setting the period T and the modulation width ΔΩ to predetermined values,
Ri, is possible to define the scope of want to detect distance frequency f _r
Set transmission center frequency f ₀ to a predetermined value
By the range of speed frequency f _d to be detected Tadashi
Can be specified.

Specifically, the following method is employed.
You. Now, the distance frequency f _r (bee
Detection frequency depending on the distance among the frequency of
Physically, the possible frequency corresponding to the speed range to be detected
The maximum value of the absolute value of the number range) is 1/1 of this repetition frequency.
Higher than twice , depending on the speed of the beat wave frequency
Speed frequency f _d ( speed frequency to be detected: Specifically,
Absolute frequency range corresponding to the distance range to be detected
To be lower than 2 times the minimum value) is the repetition frequency of the relative value is set to the modulation width (the period of the maximum frequency shift) [Delta] [omega modulation wave T (1 / T = repetition frequency) or the like, i.e. Since f _r > 2 / T and (１ ／ T)> f _d , the received wave S _r when there is one target is as follows.

[0034] _{S r = Acos [2π (f} r -f d) t] section in the reception wave [(n-1) T, ( n-1) T + T /
When subjected to first discrete Fourier transform 2], the range of speed frequency f _d is lower than 1/2 of the reciprocal of the section to be sampled and detected only the distance frequency f _r. The speed frequency _fd is detected as a phase component.

That is, DFT ｛Acos [2π (f _{r
-F d) t] -2πf d nT} } , when the f = f _r exp
(J2πf _d nT) next, when f = -f _r exp (j
2πf _d nT), and becomes zero when the f ≠ ± f _r. Also, the first discrete Fourier transform is performed for each of n = 0,. . . , N
performed for _d -1, for each distance frequencies f _r, but the time series of the phase components are obtained, which is the speed frequency f
It is equal to a sample value sequence obtained by sampling a signal having a frequency of _d at a sampling interval T. This sump
The value sequence is a discrete Fourier for the distance frequency to be detected.
Each obtained as a result of performing the conversion multiple times ( _Nd times)
This is equivalent to time series data for each distance frequency.

Further, since data for f = -f _r is unnecessary, as shown in FIG. 11, half of the data in the region of f _r <0 can be discarded, in total by this
Calculation time can be halved. For the rest of the data
And a time series of phase components corresponding to each f = _fr ( _fr > 0)
Is subjected to a second discrete Fourier transform , f = f
speed frequency f _d of a target corresponding to _r is detected.

That is, DFT (DFT @ Acos [2
_{π (f r -f d) t} ] -2πf d nT}) is, DFT {e
xp (j2πf _d nT)}, and the DFT {ex
p (j2πf _d nT)} _{is, f = (f r, f} d) When 1
And becomes 0 when f ≠ ( _fr , _fd ). Similarly, the received wave when there are a plurality of targets 14-i as in the present embodiment is as follows.

S _r = ΣA _k cos [2π (f _rk −f _dk ) t] Note that the above equation is calculated for k = 1 to M.
Therefore, when the same operation is performed on this signal, the distance frequency and the velocity frequency can be obtained for each target 14-i. This is explained in a supplementary manner.
Then, it becomes as follows.

That is, when there is one target, the first three
The received beat signal S ₍₀₎ (t) for the angular wave has the following complex
It can be represented by an elementary sine wave. _{S (0) (t) =} Aexp [j2π (f r -f d) t + jφ] received beat signal S for the (n + 1) -th triangle wave _{(n) (t)}
Becomes _{S (n) (t) =} Aexp [j2π (f r -f d) t + j2πf d nT + jφ]. Because, as mentioned above,
The phase part changes between the rising and falling sections every triangular wave cycle.
The phase portion related to the speed frequency is canceled out
This is because the phase shifts by an amount corresponding to the frequency.

With respect to this received wave, M points for each triangular wave
When the first discrete Fourier transform is performed, the velocity frequency f _d
Is lower than the reciprocal 1 / T of the section to be sampled
_Therefore, only the distance frequency _fr is detected. Also, the (n + 1) th
The k-th frequency component of the discrete Fourier transform for the
The component X _k is expressed as X _k ⁽ⁿ⁾ = X _k ⁽⁰⁾ exp [j2πf _d nT] , which is represented by the spectrum related to the distance frequency and
Has become.

Each n-th triangular wave (n = 0,..., N _d
From the result of the discrete Fourier transform for -1), each frequency
Time series data can be generated for each of several components. An example
For example, for the k-th frequency component, time series data of {X _k ⁽⁰⁾ , X _k ⁽¹⁾ ,... X _k ^(N-1) } is generated. Time system for each frequency
Each of the column data has a frequency frequency _fd as a frequency.
Sampling data of the sampling interval T of the elementary sine wave signal
Is equal to Therefore, each of the time series for each frequency
Performs the second discrete Fourier transform on
Target speed frequency spectrum of existing in a distance corresponding to the number
Is calculated.

As in this embodiment, a plurality of targets 14-i
(I = 1, ..., M), the received wave is as follows.
ing. ^{_{S (i) (t) =}} ΣA (i) exp [j2π (f r (i) -f d (i)) t + jφ (i)] Note that the above equation is assumed to be computed for k = 1 to M.
Here, multiple frequencies are discriminated by the discrete Fourier transform.
If you perform the same operation on this signal,
For each target 14-i, the distance frequency and the velocity frequency are obtained.
Can be Note that the above two discrete Fourier transforms
The algorithm is a real number represented by sin, cos
The same can be applied to a sine wave signal.

Accordingly, by performing the same operation on this signal, the distance frequency and the velocity frequency can be obtained for each target 14-i. By the way, if FFT is applied to data sampled in a finite section, a signal is distorted. This is because a rectangular window (see FIG. 9) is implied. The Fourier transform of the rectangular window has a large side lobe as shown in FIG.
Applying FFT to data sampled in a finite interval is equivalent to taking the convolution of the true spectrum and the spectrum of the rectangular window, so that side lobes occur around each spectral component and the signal is distorted.

However, by performing the window processing, the side lobe when the FFT is applied is reduced, and the distance and the relative speed can be detected more precisely.
For example, in the rectangular window, the level of the largest side lobe with respect to the peak level is −13 dB, but in the triangular window shown in FIG. 7, it is −26 dB, and in the Hanning window shown in FIG. 5, it is as small as −31 dB (FIG. 6, FIG. 8). Therefore, when window processing is performed using a triangular window or Hanning window,
The side lobe of the signal is greatly reduced as compared with the case where no window processing is performed (corresponding to the use of a rectangular window).

With the above configuration, the signal from the RF signal generating circuit 11 frequency-modulated by the triangular wave is transmitted to the transmitting antenna 1.
3 and the target 14−
The mixer 16 obtains a beat wave of the reflected wave from the i and the locally transmitted wave from the directional coupler 12, and this beat wave is
The data is digitized by the D converter 17 and tuned to the modulated wave by the window processing circuit 18 to perform window processing for each T / 2. By performing the window processing in this way and performing the discrete Fourier transform twice in the discrete Fourier transform circuit 19, the distance to the plurality of targets 14-i and the relative distance between the plurality of targets 14-i and the observer are obtained. Detecting speed is performed.

[0046] At this time, obtains a distance frequency f _r in the first discrete Fourier transform, by determining the speed frequency f _d with the second discrete Fourier transform, the distance to a plurality of targets 14-i and a plurality of targets 14 The relative speed between i and the observer is detected. That is, as shown in FIG. 13, the beat wave from a plurality of targets 14-i, the first discrete Fourier transform, as shown in FIG. 14, the distance frequency f _r
(F ₁ , f ₂ , f ₃ in the figure) are obtained, and the velocity frequency f _d (F ₁ , F ₂ , F ₃ in the figure) is obtained in the second discrete Fourier transform as shown in FIG. .

The two-time discrete Fourier transform circuit 1
In step 9, the digital data that has entered the up (or down) gradient section of the modulated triangular wave is sent to the FFT processing device, and the FFT processing is performed in the down (or up) gradient section. Data is not sent to the FFT processing unit during the down (or up) gradient section (see FIG. 12). Also, once FFT
The processed data is sequentially stored in the memory 19-2. After performing the N _d times FFT processing retrieves the data that has been stored in the memory 19-2 at each distance frequencies,
Perform FFT processing to obtain the distance frequency and velocity frequency of each target. Finally, the distance and relative speed of each target are obtained from the distance frequency and the speed frequency.

In this manner, even when a plurality of targets 14-i are present, each distance and relative speed can be accurately detected. In addition, since this device uses a digital circuit, the circuit configuration is simple and the cost can be reduced, thereby making it suitable for a vehicle-mounted radar. FIG. 16 shows simulation results obtained by using the method of the present invention to obtain distances and relative velocities for a plurality of (10) targets. Here, a plurality of calculation results (a plurality of lines) appear in one target portion because the frequency is roughly discretized with respect to the data.

[0049]

As described in detail above, the FM-C of the present invention
According to the W radar device, the detection target frequency is the detection target
The frequency modulation signal is set to a frequency higher than the speed frequency.
Has set items, preferably, the frequency modulation at a high repetition frequency twice or a rather less than the detection target rate frequency
Or, or, detected distance frequency is higher than twice the repetition frequency of the frequency-modulated wave, so that the detected speed frequency lower than half the repetition frequency of the frequency modulated wave, frequency modulation repetition frequency of the wave, since to set a modulation width <br/>, frequency set in this manner
By performing a discrete Fourier transform twice on the received beat wave resulting from the modulated signal, as a preferred mode , the distance frequency is obtained by the first discrete Fourier transform, and this distance frequency is calculated.
As a result of performing the discrete Fourier transform
By performing the second discrete Fourier transform on the obtained time series data for each distance frequency to obtain the velocity frequency, the distance to multiple targets and the relative velocity between multiple targets and the observer can be accurately detected. There are advantages that can be done.

In addition, a triangular wave can be used as a repetitive frequency modulation wave, or a discrete Fourier transform can be performed twice after performing a digitized window process on a received beat wave, so that accurate distance and relative distance can be easily obtained. The distance can be detected. Further, in the first half of the repetition period of the frequency modulation wave, data to be subjected to the discrete Fourier transform is fetched, and in the second half of the repetition period of the frequency modulation wave, the discrete Fourier transform can be performed. There is an advantage that it can be shortened.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a diagram illustrating the principle of an FM-CW radar device.

FIG. 4 is a diagram illustrating the principle of an FM-CW radar device.

FIG. 5 is a Hanning window characteristic diagram.

FIG. 6 is a side lobe characteristic diagram based on a Hanning window.

FIG. 7 is a characteristic diagram of a triangular window.

FIG. 8 is a side lobe characteristic diagram using a triangular window.

FIG. 9 is a characteristic diagram of a rectangular window.

FIG. 10 is a side lobe characteristic diagram using a rectangular window.

FIG. 11 is a diagram illustrating a frequency domain after twice discrete Fourier transform.

FIG. 12 is a diagram illustrating a relationship between FFT data capture and FFT processing.

FIG. 13 is a diagram illustrating a state in which a phase is changed due to a Doppler shift to explain the principle of multi-target identification.

FIG. 14 is a diagram illustrating a first Fourier transform for explaining the principle of multiple target identification.

FIG. 15 is a diagram illustrating a second Fourier transform for explaining the principle of multi-target identification.

FIG. 16 is a diagram showing simulation results of obtaining distances and relative velocities for a plurality of targets.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 frequency modulation wave generating circuit 1A RF signal generating circuit 2 directional coupler 3 transmitting antenna 4-i target 5 receiving antenna 6 mixer 7 A / D converter 8 window processing circuit 9 twice discrete Fourier transform circuit 10 triangular wave generator ( 11 RF signal generation circuit 12 Directional coupler 13 Transmit antenna 14-i Target 15 Receiving antenna 16 Mixer 17 A / D converter 18 Window processing circuit 19 Twice discrete Fourier transform circuit 19-1 Fourier transform processing circuit ( FFT processing circuit) 19-2 Memory 19-3 Data control circuit 20 Synchronous signal generation circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tamio Saito 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Yoji Ohashi 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited ( 72) Inventor Kawasaki Yoshihiro 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Osamu Isa 1-2-28 Goshodori, Hyogo-ku, Kobe City, Hyogo Prefecture Inside Fujitsu Ten Limited ( 56) References JP-A-3-154888 (JP, A) JP-A-3-18784 (JP, A) JP-A-2-212793 (JP, A) JP-A-62-8269 (JP, A) JP 60-263877 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/96

Claims (6)

(57) [Claims] 1. A sends a frequency modulated signal frequency-modulated with a modulation wave having a predetermined repetition frequency, respectively included in the frequency of the beat wave with an authentic manner whether these reflected waves and the local oscillation wave
Distance frequency dependent on speed and velocity frequency dependent on speed
In the FM-CW radar device for detecting the relative velocity between the distance and the target and the observer in the target or from a number of the detection target distance frequencies having detected distance information detection pairs
Frequency higher than the detection target speed frequency that has the target speed information
The frequency at which the frequency modulated signal set to be
Wave number modulation signal transmitting means, and a frequency modulation signal transmitted from the frequency modulation signal transmitting means.
By subjecting the two discrete Fourier transform on the received beat wave caused by items, distances and multiple targets manner at a plurality of characteristic manner or
With detection means for detecting the relative speed between the object and the observer
An FM-CW radar device comprising: 2. The apparatus according to claim 2, wherein said frequency-modulated signal transmitting means comprises:
The FM-CW radar device according to claim 1, wherein the FM-CW radar device is configured to frequency-modulate a modulated wave having a repetition frequency that is at least twice as high as the elephant velocity frequency. 3. The detecting device according to claim 2, wherein
Elephant distance frequencies is higher than twice the repetition frequency of the frequency modulation wave, as the detection target speed frequency is lower than half the repetition frequency of the frequency-modulated wave, and repetition frequency of the frequency modulated wave At least the modulation width
Together are also arranged to assign a, the detecting means obtains the detected distance <br/> away frequency in the first discrete Fourier transform, discrete for the detection object distance Frequency
Each distance obtained as a result of performing the Fourier transform multiple times
To the time-series data for each separated frequency, by determining the detection target speed frequency by performing a second discrete Fourier transform, the relative speed between the distance and a plurality of characteristic manner the observer at a plurality of characteristic manner or The FM-CW radar device according to claim 1, wherein the FM-CW radar device is configured to detect. 4. The FM-CW radar apparatus according to claim 1, wherein said frequency modulation signal transmitting means is configured to use a triangular wave as a repetition frequency modulation wave. 5. The apparatus according to claim 1, wherein said detection means is configured to apply a digitized window process to the received beat wave and then apply a discrete Fourier transform twice.
The FM-CW radar device as described in the above. 6. detection means, in the first half of the repetition period of the frequency modulation wave, captures data to be subjected to the discrete Fourier transform, in the second half of the repetition period of the frequency modulation wave, configured to perform a discrete Fourier transform It is characterized in that the, FM-CW radar apparatus according to claim 1.