JP2011033498A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately detect a target by a radar device for detecting a target by a holographic synthesis method, by avoiding influence due to a reduction of the intensity of a received signal as much as possible. <P>SOLUTION: Regarding to at least a first corresponding received wave and a second corresponding received wave among a plurality of holographic synthesized corresponding received waves respectively corresponding to a plurality of transmitted waves, receiving antennas in a predetermined number of at least two, among a plurality of receiving antennas which have received the first corresponding received wave, and the same predetermined number of receiving antenna, among the plurality of receiving antennas which have received the second corresponding received wave, are defined as synthesis reference antennas for synthesis. At least one of the predetermined number of pairs of synthesis reference antennas enabling phase synthesis of the corresponding received waves formed between the predetermined number of synthesis reference antennas of the first corresponding received wave and the predetermined number of the synthesis reference antennas of the second corresponding received wave, is provided as a synthesis reference antenna pair. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radar apparatus.

  Conventionally, in a radar apparatus having an array antenna with antennas arranged at equal intervals, the result of transmitting and receiving while switching the antenna to be used as a transmission antenna is holographically synthesized, so that the number of virtual antennas exceeds the number of actual antennas. There is a technique for obtaining a reception result (see, for example, Patent Documents 1 to 4).

JP 2004-198312 A JP 2005-195491 A JP 2006-91028 A JP 2006-98181 A JP 2006-308608 A JP 2007-199085 A

  2. Description of the Related Art Conventionally, there is an electronic scanning type radar apparatus that forms an array antenna in which a plurality of antennas are arranged in a line at equal intervals, forms a plurality of reception beams by calculating reception signals from the plurality of antennas, and performs scanning. In such a radar apparatus, it is possible to realize a scan equivalent to a scan using a relatively large number of antennas with a small number of antennas in practice by the holographic synthesis method.

On the other hand, an angle range (FOV: Field of) which is a range in which the radar apparatus can scan.
When there are a plurality of targets in (View), the reflected waves reflected by the targets interfere with each other and sometimes cancel each other, which can result in a lot of errors in the phase information necessary for target detection. . In such a case, if an attempt is made to detect a target based on the holographic synthesis method, it becomes difficult to detect the target accurately due to the influence of the phase error.

  In view of the above-described problems, the present invention provides a radar apparatus that performs target detection by a holographic synthesis method, avoiding as much as possible the effect of a decrease in received signal intensity, and enabling more accurate target detection. The issue is to provide.

  In order to solve the above-described problems, the present invention determines a plurality of combinations of antennas for performing holographic synthesis (corresponding to the synthesis reference antenna pair in the present invention), and performs holographic synthesis via at least one of the combinations. The configuration is to be performed. With this configuration, it is possible to appropriately select a suitable antenna combination that enables holographic synthesis even when the signal strength of the received wave is reduced, and therefore, more accurate target detection is possible.

Specifically, the present invention sequentially switches at least two transmission antennas that transmit transmission waves, and based on reception signals obtained by receiving reflected waves, which are reflection waves of a transmission wave by a target, by a plurality of reception antennas. A radar device for detecting a target, wherein a transmission wave transmitted from each of the at least two transmission antennas corresponds to a transmission wave reflected by the target via the plurality of reception antennas. Receiving means for receiving as a corresponding received wave; and combining means for obtaining reception results from a plurality of virtual receiving antennas from the plurality of receiving antennas by combining the plurality of corresponding received waves received by the receiving means; Detecting means for detecting the target based on the reception result obtained by the synthesizing means. The combining means includes the plurality of receiving antennas that have received the first corresponding received wave for at least the first corresponding received wave and the second corresponding received wave among the plurality of corresponding received waves to be combined. A predetermined number of receiving antennas and at least two receiving antennas that have received the second corresponding received wave, the predetermined number of receiving antennas are defined as combining reference antennas for combining, Between the combined reference antennas formed between the predetermined number of combined reference antennas of the first corresponding received wave and the predetermined number of combined reference antennas of the second corresponding received wave and capable of phase combining of the corresponding received waves The first corresponding received wave and the second corresponding received wave are combined based on the received wave phase via at least one combined reference antenna pair among the predetermined number of combined reference antenna pairs.

  In the radar apparatus, the reception unit receives the reflected wave from the target corresponding to the transmission wave sequentially transmitted from at least two transmission antennas. In this case, the reception wave corresponding to each transmission wave is referred to as a corresponding reception wave, and since the transmission wave is output from at least two transmission antennas, the first corresponding reception wave and the second corresponding reception wave exist as the corresponding reception waves. . In addition, regarding the transmission of the transmission wave and the reception of the reception wave in the radar apparatus according to the present invention, a transmission antenna and a reception antenna may be provided, and the reception antenna is switched by switching the function of one antenna. Or you may employ | adopt the structure which functions as a transmission antenna. Therefore, the transmitting antenna and the receiving antenna in the radar device are concepts including a case where they are physically the same antenna and a case where they are physically different antennas.

  As described above, when the receiving unit receives at least the first corresponding received wave and the second corresponding received wave, the combining unit performs holographic synthesis of both the corresponding received waves, and the detecting unit further converts the received wave into the combined received wave. Based on this, target detection is performed. Here, in the synthesis of the corresponding received waves by the combining means, two or more predetermined number of combining reference antennas are determined for each of the first corresponding received wave and the second corresponding received wave, and as a result, the same number of hollow antennas are determined. A combined reference antenna pair that is a combination of combined reference antennas for graphic synthesis is formed. The combined reference antennas included in this combined reference antenna pair are clearly defined that the phases of the corresponding received waves received there have a predetermined correlation in theory (for example, the same phase, etc.) ), And the phase synthesis of both of the received waves can be performed.

  As described above, in the above-described radar apparatus, in the combination of the first corresponding received wave and the second corresponding received wave, the combination reference antenna pair that allows the combination is always set to a predetermined number of two or more. Therefore, even if a situation in which the influence of the phase error due to a decrease in signal intensity cannot be ignored due to interference of reflected waves from the target, etc., a combined reference antenna suitable for combining among a predetermined number of combined reference antenna pairs By using the pair, it is possible to avoid the influence of the phase error as much as possible, and more accurate target detection is realized. In addition, in the synthesis of the corresponding received wave, holographic synthesis is practically possible through one synthetic reference antenna pair, but synthesis is also possible via two or more synthetic reference antenna pairs. .

  Here, in the radar apparatus, the combining unit is configured to output the combination reference when the reception wave intensity of each combination reference antenna included in each combination reference antenna pair exceeds the reference signal intensity in the predetermined number of combination reference antenna pairs. The first pair of received waves and the second pair of received waves may be combined using the antenna pair as the one combination reference antenna pair. That is, more accurate target detection is possible by using a combination reference antenna pair having sufficient signal strength to perform appropriate holographic synthesis.

  Further, in the radar apparatus, the combining unit may receive a received wave phase via a combined reference antenna pair having the strongest received wave intensity of each combined reference antenna included in the predetermined number of combined reference antenna pairs. The first corresponding received wave and the second corresponding received wave based on the above may be combined. In other words, when combining the first corresponding received wave and the second corresponding received wave, by combining them through the combination reference antenna pair having the highest signal strength, it is possible to combine with the least influence of the phase error. Is done. The signal strength of the combined reference antenna pair is defined as a predetermined signal strength determined based on the signal strength of the combined reference antenna included therein, for example, an average value of the signal strength of the combined reference antenna included therein, or the like. The

  Further, in the radar apparatus, the combining means includes the received signal strengths of the predetermined number of combined reference antennas of the first corresponding received wave and the predetermined number of combined reference antennas of the second corresponding received wave. Based on the intensity of each received signal, it may have a correction phase calculating means for calculating a correction phase for combining the first corresponding received wave and the second corresponding received wave. The means may combine the first corresponding received wave and the second corresponding received wave based on the correction phase calculated by the correction phase calculating means via the at least one combination reference antenna pair. In other words, by calculating the correction phase for synthesis based on the signal strength of the first corresponding received wave and the second corresponding received wave, and using this to synthesize both corresponding received waves, a more accurate target Is detected.

  In the radar apparatus, the combining unit includes: a determining unit that determines whether a signal strength of a combined reference antenna included in the at least one combined reference antenna pair is smaller than a reference signal strength; When it is determined that the signal strength of the combined reference antenna is smaller than the reference signal strength, one combined reference antenna corresponding to the first corresponding received wave in the combined reference antenna pair is excluded from the plurality of receiving antennas. Based on the received wave phase of the remaining receiving antenna formed, first estimating means for estimating the received wave phase of the one combined reference antenna, and similarly, the signal strength of the combined reference antenna is higher than the reference signal strength. When determined to be small, the other combined reference antenna corresponding to the second corresponding received wave among the combined reference antenna pair is set to the plurality of combined reference antennas. Second estimation means for estimating the received wave phase of the other combined reference antenna based on the received wave phase of the remaining receiving antenna, which is formed by removing from the receiving antenna. The combining unit calculates a phase difference between the received wave phase estimated by the first estimating unit and the received wave phase estimated by the second estimating unit, and receives the reception signal via the one combined reference antenna pair. The first corresponding received wave and the second corresponding received wave may be combined based on the wave phase and the phase difference.

  That is, when the combined reference antenna pair that combines the two received waves does not receive a received wave with sufficient signal strength for combining, the first estimating unit and the second estimating unit perform the combining reference antenna. By using the phase of the corresponding received wave by the receiving antenna excluding the receiving antenna included in the pair, the phase of the first corresponding received wave and the second corresponding received wave by the receiving antenna included in the combination reference antenna pair is estimated. The Then, by using the phase difference between the two estimated phases, the combination of the two corresponding received waves is realized. With such a configuration, even if the signal strength is weak in the combination reference antenna pair, it is possible to realize holographic combination as accurate as possible.

  In a radar apparatus that performs target detection by the holographic synthesis method, it is possible to avoid as much as possible the influence of a decrease in the intensity of the received signal and to perform more accurate target detection.

It is a figure which shows the outline of a structure of the radar apparatus which concerns on embodiment. It is a figure which shows the outline of arrangement | positioning of the antenna which concerns on embodiment. It is the 1st figure which showed a mode that the reflected electromagnetic wave from a target was received with the antenna which concerns on embodiment. In the embodiment, when the transmission / reception of radar waves as shown in FIG. 3 is performed by sequentially switching antennas ch1 and ch5 as transmission antennas, the phase of the radio wave transmitted from antenna ch1 and received by antenna ch1 is used as a reference. It is a figure which shows the relative phase of the received electromagnetic wave in each receiving antenna. FIG. 4 is a diagram illustrating a relative phase in each receiving antenna when the antenna ch1 and ch5 are sequentially switched as transmitting antennas in the radar apparatus having the antenna arrangement illustrated in FIG. 3. It is a 1st flowchart which shows the flow of the target detection process in the radar apparatus which concerns on embodiment. It is a 2nd flowchart which shows the flow of the target detection process in the radar apparatus which concerns on embodiment. It is a 3rd flowchart which shows the flow of the target detection process in the radar apparatus which concerns on embodiment. It is a 4th flowchart which shows the flow of the target detection process in the radar apparatus which concerns on embodiment. It is the 2nd figure which showed a mode that the reflected electromagnetic wave from a target was received with the antenna which concerns on embodiment. In the embodiment, the phase of the radio wave transmitted from the antenna ch1 and received by the antenna ch1 when the transmission / reception of the radar wave as shown in FIG. 10 is performed by sequentially switching the antennas ch1, ch2, and ch5 as transmission antennas. It is a figure which shows the relative phase of the received electromagnetic wave in each receiving antenna on the basis of. FIG. 11 is a diagram illustrating a relative phase in each reception antenna when the antenna ch1, ch2, and ch5 are sequentially switched as transmission antennas in the radar apparatus having the antenna arrangement illustrated in FIG. 10. It is a graph which shows the range which can detect the angle by the virtual antenna for wide FOV which concerns on embodiment, and the virtual antenna for narrow FOV.

  Embodiments of a radar apparatus according to the present invention will be described below with reference to the drawings. The radar apparatus according to the present embodiment is mounted on a vehicle and can be used to detect targets around the vehicle such as other vehicles. The target detection result is output to an in-vehicle storage device, an ECU (Electrical Control Unit), or the like, and can be used for vehicle control or the like. However, the radar apparatus according to the present embodiment may be used for purposes other than the in-vehicle radar apparatus.

  FIG. 1 is a diagram schematically illustrating the configuration of a radar apparatus 1 according to the present embodiment. The radar apparatus 1 according to the present embodiment includes antennas ch1 to ch6, a distributor 19, a transmission unit 11, a reception unit 12, a synthesis unit 14, a detection unit 15, and an output unit 16. However, when the radar apparatus according to the present invention is implemented in another embodiment, the configuration of the synthesizing unit 14, the detection unit 15, the output unit 16, and the like may be omitted from the radar apparatus. These configurations can be realized by a computer connected to the outside of the radar apparatus. A general-purpose or dedicated processor can be used for each component such as the synthesis unit 14, the detection unit 15, and the output unit 16. Further, a combination of a plurality of processors may be included in one configuration, or a single processor having multiple functions in a plurality of configurations may be used.

The transmission unit 11 transmits a radar transmission wave using any one of the antennas ch1 to ch6 as a transmission antenna. In the radar apparatus 1 according to the present embodiment, any of the antennas ch1 to ch6 can be used for transmission. However, in implementing the radar apparatus 1 according to the present invention, a plurality of antennas in the array antenna may be used. Of these, at least two or more antennas may be used as transmitting antennas. In the present embodiment, the transmission unit 11 transmits a radar transmission wave by sequentially switching the two antennas ch1 and ch5 as a transmission antenna. In this embodiment, an FM-CW (Frequency Modulated Continuous Wave) radar transmission wave is used for radio waves transmitted and received by the radar apparatus 1. According to the FM-CW method, the target phase, distance, and relative velocity can be measured from the reflected radio wave because the relative phase due to the target angle, the time delay due to the target distance, and the Doppler shift due to the target velocity can be obtained. I can do it.

  The receiving unit 12 receives a reflected radio wave from the target using an antenna that is not transmitting a radar transmission wave among the antennas ch1 to ch6 as a reception antenna. In the radar apparatus 1 according to the present embodiment, immediately after transmitting the radar transmission wave from the transmission antenna, the transmission antenna is switched to the reception antenna in a time division manner to receive the reflected radio wave of the radar transmission wave transmitted by the own antenna. Is possible. For example, even when the antenna ch1 is used as a transmission antenna, the reflected radio wave of the radar transmission wave transmitted from the antenna ch1 can be obtained by switching the antenna ch1 to the reception mode immediately after transmission of the radar transmission wave from the antenna ch1. The antenna ch1 is also received. That is, in this embodiment, when any of the two antennas ch1 and ch5 is used as a transmission antenna, all six antennas ch1 to ch6 are used as reception antennas.

  In the present embodiment, the synthesis unit 14, the detection unit 15, and the output unit 16 are realized by a computer as the control unit 13 executing a control program. The control unit 13 used here includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a CPU (Central Processing Unit) that controls the entire system by processing instructions and data expanded in the RAM, and the like. A computer having an EEPROM (Electrically Erasable and Programmable Read Only Memory) in which various data used by the system such as various programs loaded on the computer and calculation results obtained by the target detection process are stored.

  The control unit 13 controls each component provided in the radar apparatus 1. Specifically, the control unit 13 switches the transmission / reception mode in the antennas ch1 and ch5 by controlling the distributor 19 in accordance with the transmission timing of the radar transmission wave and the reception timing of the reflected radio wave from the target. In this embodiment, the transmission antenna receives the reflected radio wave of the radar transmission wave transmitted by the own antenna by switching the transmission mode and the reception mode at high speed in a time division manner.

  The synthesizer 14 holographically synthesizes the reception result of the reflected radio wave based on the radar transmission wave transmitted from different transmission antennas at different timings. By such holographic synthesis, it is possible to obtain reception results with virtual antennas that are larger than the number of antennas (six) that the radar apparatus 1 physically has. In this embodiment, each received wave by the antennas ch1 to ch6 corresponding to radar transmitted waves transmitted from different transmitting antennas at different timings is referred to as a corresponding received wave. Therefore, in the present embodiment, there will be a first corresponding received wave and a second corresponding received wave, which will be described later.

The detection unit 15 calculates the angle, distance, and speed of the target based on the reception result by the virtual antenna (combined received wave synthesized from two corresponding received waves). The output unit 16 determines the target detection result (information including the target angle, distance, and speed) by the detection unit 15, and sends the determined detection result to the ECU connected to the radar apparatus 1. Output. In the present embodiment, since the output unit 16 outputs a highly accurate target detection result, the in-vehicle ECU can control the engine, the in-vehicle navigation device, and the like based on the highly accurate target detection result. . Detailed operations of the components included in the control unit 13, particularly detailed operations of the combining unit 14, will be described later.

  FIG. 2 is a diagram schematically illustrating the arrangement of the antennas ch1 to ch6 according to the present embodiment. In this embodiment, triplate antennas ch1 to ch6 in which antenna elements are arranged in two rows are used. The antennas ch1-ch6 form an array antenna by being arranged in a line at a predetermined interval with respect to adjacent antennas. Here, with respect to the antennas ch1 to ch6, as a distance between the antennas, a standard distance d (1.8λ (λ: transmission wave wavelength) in the present embodiment) employed in a conventional radar device developed for in-vehicle use. ) Is adopted. This antenna interval is an interval determined in consideration of antenna size, output, interference, and the like. When the antenna interval is 1.8λ, FOV (Field of View) is Arcsin (λ / (2 * 1.8λ)) ≈16.12 degrees.

  FIG. 3 is a diagram illustrating a state where the reflected radio waves from the target are received by the antennas ch1 to ch6 according to the present embodiment. In the radar apparatus 1 according to the present embodiment, the angle at which the target is positioned by the relative phase (delay) of the reflected radio wave transmitted from the transmitting antenna and received by the receiving antennas arranged in a line (indicated by α in FIG. 3). Is calculated. According to FIG. 3, the relative phase of the reflected radio wave received at antennas ch1-ch6 is α between adjacent antennas.

  Here, when the radar apparatus 1 detects the target and the reflected waves from a plurality of targets interfere with each other and the intensity thereof decreases, the phase of the received wave by each of the receiving antennas ch1 to ch6 is accurately detected. Which may have an undesirable effect on the holographic synthesis of the received wave. In other words, when two received waves are synthesized by holographic synthesis, it is assumed that the phase of the corresponding received wave is the same for each antenna that is a reference for synthesis. If it cannot be detected, the holographically synthesized received wave is shifted by the phase error of the corresponding received wave as a result, and accurate target detection becomes difficult.

  Therefore, in the radar apparatus 1 according to the present embodiment, a plurality of (hereinafter referred to as “combined reference antenna pairs”) of antennas (hereinafter referred to as “combined reference antennas”) for holographically combining corresponding received waves (hereinafter referred to as “combined reference antenna pairs”). In this embodiment, two) are set. In the holographic synthesis by the synthesizing unit 14, the first corresponding received wave, which is a received wave by each antenna ch1-ch6, corresponding to the transmitted wave from the antenna ch1 via the two synthesized reference antenna pairs, Then, combining with the second corresponding received wave, which is the received wave by each antenna ch1-ch6, corresponding to the transmitted wave from antenna ch5 is performed. Details will be described below.

FIG. 4 shows that in this embodiment, the transmission / reception of the radar wave as shown in FIG. 3 is transmitted from the antenna ch1 and received by the antenna ch1 when the antennas ch1 and ch5 are sequentially switched as transmission antennas. It is a figure which shows the relative phase of the received electromagnetic wave in each receiving antenna on the basis of the phase of the 1st corresponding received wave (namely, delay 0). The relative phase of the first corresponding received wave transmitted from the antenna ch1 and received by the antenna ch2 is α, and thereafter, the relative phase of the first corresponding received wave received by the antennas ch3, ch4, ch5, and ch6 is 2α. 3α, 4α, and 5α. In addition, the relative phase of the second corresponding received wave transmitted from the antenna ch5 and received by the antenna ch1 is 4α, and thereafter the relative phase of the second corresponding received wave received by the antennas ch2, ch3, ch4, ch5, and ch6. Phase is 5α, 6α, 7α respectively
, 8α, 9α. Thus, in the radar apparatus 1, the relative phase in the case of antenna ch1 transmission and antenna ch5 reception and the relative phase in the case of antenna ch5 transmission and antenna ch1 reception are also 4α, and the antenna ch1 transmission and antenna ch6 reception are the same. Similarly, the relative phase in the case of antenna ch5 transmission and antenna ch2 reception is 5α. Therefore, holographic synthesis is performed by the synthesizing unit 14 by determining the antennas having the same relative phase in each corresponding received wave as a synthesis reference antenna pair.

  The relationship between the form of transmission / reception of each antenna shown in FIG. 4 and the relative phase at the receiving antenna is shown as an image in FIG. FIG. 5 is a diagram illustrating a relative phase in each reception antenna when the antennas ch1 and ch5 are sequentially switched as transmission antennas in this embodiment. In FIG. 5, antennas that have transmitted and received are indicated by black circles, and antennas that have only received are indicated by white circles. Further, the relative phase with reference to the phase at the time of antenna ch1 transmission and antenna ch1 reception shown in FIG. As shown in FIG. 5, in the first corresponding reception wave corresponding to the transmission wave from the antenna ch1, two antennas, antennas ch5 and ch6, are defined as the synthesis reference antennas for holographic synthesis. In the second corresponding reception wave corresponding to the transmission wave from the antenna ch5, two antennas of the antennas ch1 and ch2 are defined as the synthesis reference antennas for holographic synthesis. Then, a pair of combining reference antennas capable of holographic combining, that is, antenna ch5 at the time of antenna ch1 transmission, antenna ch1 at the time of antenna ch5 transmission, antenna ch6 at the time of antenna ch1 transmission, and antenna ch5 transmission The pair of antennas ch2 is a first combined reference antenna pair and a second combined reference antenna pair, respectively.

  As described above, in the radar apparatus 1, the signal strengths of the first corresponding received wave and the second corresponding received wave due to the presence of a plurality of targets and the like are determined by determining two combining reference antenna pairs for holographic combining. In spite of the decrease in the frequency, both received waves can be combined more accurately. In the prior art, since the number of combined reference antenna pairs is one, if the intensity of the received wave at the antenna included in the combined reference antenna pair becomes weak, it is strongly affected by the phase error that has occurred, The phase error is added to the holographically synthesized received wave, making accurate target detection difficult. However, since the radar apparatus 1 according to the present invention provides a plurality of combined reference antenna pairs (two in this embodiment) as described above, even if the received wave intensity of the antenna included in one combined reference antenna pair is weak. It is possible to compensate for this by using the other combination reference antenna pair and the like, so that accurate target detection can be realized.

  Therefore, specific control of holographic synthesis of the first corresponding received wave and the second corresponding received wave and target detection when a plurality of combination reference antenna pairs are determined as shown in FIG. Description will be made with reference to FIG. 6 to 9 are flowcharts illustrating the flow of target detection control in the radar apparatus 1 according to the present embodiment. The processing shown in this flowchart is executed by the control unit 13 that executes the control program after the radar apparatus 1 is started, particularly, the holographic synthesis process by the synthesis unit 14. Note that the processing start timing may be in accordance with a target detection request by a computer or ECU connected to the outside of the radar device 1. Further, the processing order shown in each drawing is an example, and the processing order may be appropriately rearranged according to the embodiment.

<Target detection control (1)>
In S101, the reception unit 12 transmits the first corresponding reception wave corresponding to the transmission wave transmitted from the antenna ch1 by the transmission unit 11 and the transmission wave transmitted from the antenna ch5 via the antenna ch1-ch6. The two-corresponding reception wave is received, and the control unit 13 acquires the reception result. When the process of S101 ends, the process proceeds to S102.

  In S102, a combined reference antenna pair (hereinafter referred to as a “first combined reference antenna pair”) formed by antennas ch5 and ch1 as a combined reference antenna and antennas ch6 and ch2 as a combined reference antenna shown in FIG. The signal strengths of the first corresponding received wave and the second corresponding received wave received at each of the combined reference antenna pairs (hereinafter referred to as “second combined reference antenna pairs”) formed in (1) are detected.

  After that, in S103, it is determined whether the detected signal strength of each corresponding received wave has a reference signal strength equal to or higher than a reference signal strength, and a combined reference antenna pair including a combined reference antenna having the reference signal strength is Extracted as a combination reference antenna pair for performing holographic synthesis. This reference signal strength is such a signal strength that it can be avoided that a relatively large phase error occurs in the phase information contained therein because the signal strength of the corresponding received wave is relatively weak. That is, the reason why the reference signal strength is set is that, if the signal strength of the corresponding received wave is equal to or higher than the reference signal strength, the phase information attached to the corresponding received wave can be read relatively accurately. It depends. Specifically, if the signal strength when received by the antenna ch2 that is the combined reference antenna in the second corresponding received wave is weaker than the reference signal strength, in S103, the first combined reference that does not include the antenna ch2 The antenna pair is extracted as a combined reference antenna pair for performing holographic combining.

  In S104, holographic synthesis of the first corresponding received wave and the second corresponding received wave is performed via the combination reference antenna pair extracted in S103. In the present embodiment, since two combined reference antennas for the first corresponding received wave requirement and two combined reference antennas for the second corresponding received signal requirement are determined, reception after holographic synthesis is performed as shown in FIG. The wave is formed as a reception wave by 10 virtual antennas. For example, as described above, when only the first combined reference antenna pair is extracted in S103, the phase of the antenna ch5 in the first corresponding received wave is overlapped with the phase of the antenna ch1 in the second corresponding received wave. , Holographic synthesis of the corresponding received waves. At this time, as the phase information of the sixth virtual antenna after the holographic synthesis, the phase information of the antenna ch2 in the second corresponding received wave determined to have low signal strength is not used, and the antenna in the first corresponding received wave is not used. The phase information of ch6 is used. This is because the phase information of the antenna ch2 in the second corresponding received wave is likely to contain many phase errors as described above.

  As another form of holographic synthesis, consider a case where two of the first synthesis reference antenna pair and the second synthesis reference antenna pair are extracted in the process of S103. In this case, the phase information at the antennas included in each combination reference antenna pair is an error level that is determined to have no problem in performing the holographic combination. Therefore, when combining the first corresponding received wave and the second corresponding received wave, one of the first combined reference antenna pair and the second combined reference antenna pair may be appropriately used for holographic combining. Further, the phase difference between the phase difference between the received wave phases of the antenna ch5 and the antenna ch1 in the first combined reference antenna pair and the phase difference between the received wave phases of the antenna ch6 and the antenna ch2 in the second combined reference antenna pair is reduced. One pair of combined reference antennas may be used.

When the process of S104 ends, the process proceeds to S105. In S105, the target angle based on the result of holographic synthesis in S104 is calculated by the detection unit 15. In addition, since the technique which calculates a target angle based on the relative phase of the reflected radio wave received in the array antenna is a prior art, detailed description is abbreviate | omitted. Further, since the radar apparatus 1 according to the present embodiment transmits the radar transmission wave by the FM-CW method, the distance of the target is determined from the time delay of the received radio wave due to the target distance and the Doppler shift due to the target speed. Also, the speed can be calculated. The target detection result obtained in S105 is output to the ECU or the like connected to the radar apparatus 1 by the output unit 16. Thereafter, the processing from S101 to S105 is repeated, so that the radar apparatus 1 according to the present embodiment periodically detects the target and outputs the detection result to the ECU or the like.

  According to the target detection control, the radar apparatus 1 has a plurality of combined reference antenna pairs for performing holographic combining, and among them, a combined reference antenna whose received signal strength is equal to or higher than a predetermined reference signal strength. Since the holographic synthesis is performed via the pair, the influence of the phase error can be eliminated as much as possible. As a result, more accurate detection of the target can be realized.

<Target detection control (2)>
Next, second target detection control for target detection by the radar apparatus 1 will be described with reference to FIG. In this control, the same reference numerals are assigned to the same processes as those in the first target detection control, and detailed description thereof is omitted. In this control, when the process of S102 ends, the process proceeds to S201. In S201, a combined reference antenna pair having the highest signal strength is extracted from the two combined reference antenna pairs. Here, the signal strength of the combined reference antenna pair is determined based on the signal strength of the received wave from the combined reference antenna included therein. For example, the received signal strength of the two combined reference antennas included in the combined reference antenna pair is determined. It can be defined as the average value of signal strength. Other definitions are also possible. When the process of S201 ends, the process proceeds to S202.

  In S202, holographic synthesis of the first corresponding received wave and the second corresponding received wave is performed via the combination reference antenna pair having the highest signal intensity extracted in S201. In other words, in this control, the combination reference antenna pair with the strongest signal strength of the received wave is always selected from a plurality of combination reference antenna pairs, so that the influence of signal errors in holographic synthesis is avoided as much as possible. Thus, more accurate detection of the target can be realized.

<Target detection control (3)>
Next, third target detection control for target detection by the radar apparatus 1 will be described with reference to FIG. In this control, the same reference numerals are assigned to the same processes as those in the first target detection control, and detailed description thereof is omitted. In this control, when the process of S102 ends, the process proceeds to S301.

  In S301, for the holographic synthesis based on the signal strength of the received wave by the synthesis reference antennas (four synthesis reference antennas in the case of this control) included in the first synthesis reference antenna pair and the second synthesis reference antenna pair. The correction phase is calculated. Specifically, among the two combined reference antenna pairs, the combined reference antenna pair included in the combined reference antenna pair having a high average value of the signal strength of the received waves by the two combined reference antennas included therein. According to the received wave intensity, the phases at the respective combined reference antennas are weighted and averaged to calculate a corrected phase. For example, when the ratio of the signal strength of the antenna ch5 that is the combined reference antenna and the signal strength of the antenna ch1 that is the combined reference antenna is 4: 1 in the first combined reference antenna pair, each received wave phase (α5 , Α1) is calculated as a correction phase by a phase α ′ (= (4 · α5 + α1) / 5) obtained by weighted averaging with 4: 1. When the process of S301 ends, the process proceeds to S302.

In S302, based on the correction phase calculated in S301, holographic synthesis of the first corresponding received wave and the second corresponding received wave is performed via the combination reference antenna pair for which the correction phase has been calculated. Explaining according to the above example, in the first corresponding received wave corresponding to the antenna ch5 that is the combined reference antenna, the phases of the other antennas ch1-ch4 and ch6 are shifted so that the phase of the antenna ch5 becomes the correction phase α ′. Let On the other hand, in the second corresponding received wave corresponding to the antenna ch1 which is the combined reference antenna, the phases of the other antennas ch2-ch6 are shifted so that the phase of the antenna ch1 becomes the correction phase α ′. As a result, holographic synthesis of the first corresponding received wave and the second corresponding received wave is performed. When the process of S302 ends, the process proceeds to S105, where target detection is performed.

  According to this control, holographic synthesis using a correction phase corresponding to the signal strength of the received wave is performed via a synthesis reference antenna pair having a high average signal strength among a plurality of synthesis reference antenna pairs. As a result, the influence of the signal error can be avoided as much as possible, and thus more accurate detection of the target can be realized. Note that the calculation of the correction phase may be performed by each of the two combined reference antenna pairs. In this case, in the combined reference antenna pair in which the average value of the signal strength of the received waves by the two combined reference antennas included in each combined reference antenna pair is high, the above-described portions are excluded except for the portions corresponding to the remaining combined reference antenna pairs. Each corresponding received wave is synthesized based on the corrected phase, and for the part corresponding to the remaining synthesized reference antenna pair, the corrected phase calculated for the synthesized reference antenna pair is received by holographic synthesis. It may be captured as part of the wave phase. Further, the calculation of the correction phase by the weighted average does not have to be proportional to the signal intensity. As the signal strength increases, a weighted average in which the weight is increased exponentially, quadratic, or cubically may be performed.

<Target detection control (4)>
Next, a fourth target detection control for target detection by the radar apparatus 1 will be described with reference to FIG. Note that this control is an advanced control of the first target detection control, and the same reference numerals are assigned to the same processing as that, and the detailed description thereof is omitted. In this control, when the process of S103 is completed, the determination in S401 is performed.

  In S401, based on the extraction result in S103, it is determined whether or not the extracted combined reference antenna pair exists. That is, it is determined in S401 whether or not a combined reference antenna pair having a reference signal strength suitable for holographic combining has not been extracted. If a negative determination is made here, the processing of S104 and S105 is sequentially performed as in the first target detection control. On the other hand, if a positive determination is made, the process of S402 is performed.

  In S402, estimation of each phase of the first corresponding received wave and the second corresponding received wave by the combined reference antenna included in either the first combined reference antenna pair or the second combined reference antenna pair is performed. Done. Here, the reason why the phase estimation is performed only for one combined reference antenna pair is that one combined reference antenna pair for which holographic combining is performed is sufficient. In this embodiment, the phases of the first corresponding received wave and the second corresponding received wave received by the antenna ch5 and the antenna ch1 included in the first combined reference antenna pair are estimated.

  Here, specific phase estimation will be described. The phase estimation of the first corresponding received wave by the antenna ch5 is performed by the first antenna received from the antennas ch1 to ch4 that are not included in the combined reference antenna group determined to have a low signal strength and whose signal strength is equal to or higher than the reference signal strength. The estimation phase θ1 is calculated based on the phase of the corresponding received wave. As an example of estimation, the antenna ch5 is obtained by the least square method based on the phase of the first corresponding received wave received by the antenna having the signal strength equal to or higher than the reference signal strength among the antennas ch1 to ch4 and the distance between the antennas. The phase of the first corresponding received wave is estimated. Similarly, the phase estimation of the second corresponding received wave by the antenna ch1 is also received by the antenna whose signal strength is equal to or higher than the reference signal strength among the antennas ch3-ch6 that are not included in the combined reference antenna group determined to have low signal strength. The estimated phase θ2 is calculated based on the phase of the received second corresponding received wave. When the process of S402 ends, the process proceeds to S403.

In S403, the phase difference Δθ between the phase θ1 of the first corresponding received wave and the phase θ2 of the second corresponding received wave in the first combined reference antenna pair estimated in S402 is calculated. Thereafter, in S404, holographic synthesis of the first corresponding received wave and the second corresponding received wave based on the phase difference Δθ is performed. Specifically, when the second corresponding received wave is combined with the first corresponding received wave via the first combination reference antenna pair, the entire second corresponding received wave is shifted by the phase difference Δθ. When the process of S404 ends, the process proceeds to S105, and target detection is executed.

  According to this control, even if the signal strengths of the corresponding received waves by the first combined reference antenna pair and the second combined reference antenna pair are not sufficient for holographic combining, the above phase estimation is performed to obtain a relatively accurate Holographic synthesis can be realized. As a result, more accurate detection of the target can be realized.

  A second embodiment of the radar apparatus 1 according to the present invention will be described below. As shown in FIG. 10, regarding the antenna interval of the radar apparatus 1 according to the present embodiment, the interval between the antenna ch1 and the antenna ch2 is 1.5 times the antenna interval d of the antenna ch2-ch6. 2d (2.7λ in this embodiment) is adopted. With this configuration, the detection unit 15 of the radar apparatus 1 calculates a target angle based on a reception result by a narrow FOV virtual antenna, which will be described later, and calculates a target angle based on a reception result by a wide FOV virtual antenna. Thus, the target detection result in the FOV equivalent to the conventional one and the target detection result in the FOV wider than the conventional one can be obtained.

  The antenna employed in the present embodiment is a two-row antenna (see FIG. 2; however, the antenna interval is different from the interval of the present embodiment). Since it has an antenna characteristic of −10 dB or more up to 30 degrees, a ghost caused by a reflected radio wave from a target located outside the FOV is detected in the FOV. Therefore, the target angle calculation result based on the narrow FOV virtual antenna is corrected by the detection unit 15 using the target angle calculation result based on the wide FOV virtual antenna, thereby correcting the target angle calculation result based on the narrow FOV virtual antenna. It is also possible to remove ghosts contained in the. Details of the ghost determination process will be described later.

  Here, FIG. 11 shows that in this embodiment, the transmission / reception of the radar wave shown in FIG. 10 is transmitted from the antenna ch1 when the antennas ch1, ch2, and ch5 are sequentially switched as transmission antennas, and is transmitted from the antenna ch1. It is a figure which shows the relative phase of the received radio wave in each receiving antenna on the basis of the phase of the received radio wave. The relative phase of the radio wave transmitted from the antenna ch1 and received by the antenna ch2 is 3 / 2α. Similarly, the relative phase of the radio wave transmitted from the antenna ch2 and received by the antenna ch1 is 3 / 2α. The relative phase in the case of antenna ch2 transmission and antenna ch5 reception and the relative phase in the case of antenna ch5 transmission and antenna ch2 reception are 12 / 2α, and the relative phase in the case of antenna ch2 transmission and antenna ch6 reception The relative phase in the case of antenna ch5 transmission and antenna ch3 reception is 14 / 2α.

Here, the received wave by antenna ch1-ch6 when antenna ch1 is used as a transmitting antenna is the first corresponding received wave, and the received wave by antenna ch1-ch6 when antenna ch2 is used as the transmitting antenna is the second corresponding received wave. The received wave by the antennas ch1 to ch6 when the antenna ch5 is used as a transmitting antenna is defined as a third corresponding received wave. At this time, FIG. 12 shows a relative phase in each corresponding received wave. According to FIG. 12, the relative phase of the received radio wave received by antenna ch3-ch6 during antenna ch1 transmission and the relative phase of the received radio wave received by antenna ch2-ch5 during antenna ch2 transmission are When holographic synthesis is performed via one synthetic reference antenna pair (antenna ch2 in the first corresponding received wave and antenna ch1 in the second corresponding received wave), the relative phase of each received radio wave becomes an interval of 1 / 2α.
It can be seen that reception results obtained by eight virtual antennas arranged at intervals of / 2d (0.9λ) are obtained. That is, in this embodiment, an antenna provided with an even wider interval 3 / 2d is arranged in an array antenna provided physically with an interval d, and the transmission / reception results are changed by holographic synthesis by switching the transmission antenna. Actually, it is possible to obtain a reception result equivalent to the reception result by the antenna with the interval 1 / 2d, which is difficult to install due to problems such as inter-antenna interference. Since the eight virtual antennas with the interval 1 / 2d have a wider FOV (Arcsin (λ / (2 * 0.9λ)) ≈33.7 degrees) than the antenna with the interval d, the virtual antenna for the wide FOV Can be used.

  In the present embodiment, the relative phase of the received radio wave received by the antenna ch2-ch6 during the antenna ch2 transmission and the relative phase of the received radio wave received by the antenna ch2-ch6 during the antenna ch5 transmission are: The second combined reference antenna pair (antenna ch5 in the second corresponding received wave and antenna ch2 in the third corresponding received wave) and the third combined reference antenna pair (antenna ch6 in the second corresponding received wave and antenna ch3 in the third corresponding received wave) ) Can be used to obtain reception results with eight virtual antennas arranged at intervals d, that is, reception results with more virtual antennas than the actual number of antennas. . Further, the eight virtual antennas with the spacing d have a narrow FOV (about 16.12 degrees) with respect to the eight virtual antennas with the spacing ½d, and therefore can be used as a narrow FOV virtual antenna.

  Then, in the holographic synthesis of the second corresponding received wave and the third corresponding received wave, a plurality (two in the case of the present embodiment) of combination reference antenna pairs are determined as in the case of the first embodiment described above. Therefore, the first to fourth target detection controls described above are applied, so that more accurate target detection is possible.

  Here, the detail of the ghost determination process mentioned above is demonstrated below. FIG. 13 is a graph showing a range in which an angle can be detected by the wide FOV virtual antenna and the narrow FOV virtual antenna according to the present embodiment. The horizontal axis of the graph indicates the actual target angle, and the vertical axis of the graph indicates the angle at which the target is detected by the radar apparatus 1. A thick line indicates angle detection when a narrow FOV virtual antenna is used, and a thin line indicates angle detection when a wide FOV virtual antenna is used.

  For example, when the target is arranged at an angle indicated by x on the horizontal axis in the graph of FIG. 13, in a virtual antenna for a narrow FOV, that is, an antenna having an FOV equivalent to the actual antenna interval d, the vertical axis A target is detected at an angle indicated by a broken line x, and a ghost is generated. Therefore, in this embodiment, the occurrence of a ghost is determined by comparing the detection result by the narrow FOV virtual antenna and the detection result by the wide FOV virtual antenna. That is, in the example shown above, when the target is arranged at the angle indicated by x on the horizontal axis, the wide FOV virtual antenna detects the target at the correct angle indicated by the solid line x on the vertical axis, and narrows it. The target indicated by the broken line x detected by the FOV virtual antenna is not detected. Therefore, it can be determined that the target indicated by the broken line x detected by the narrow FOV virtual antenna is a ghost.

DESCRIPTION OF SYMBOLS 1 ... radar apparatus 11 ... transmission part 12 ... reception part 13 ... control part 14 ... synthesis part 15 ... detection part 16 ... output part 19 .... Distributor ch1-ch6 ... Antenna

Claims (5)

A radar device that detects a target based on reception signals obtained by sequentially switching at least two transmission antennas that transmit transmission waves and receiving reflected waves, which are reflected from the transmission waves by a plurality of reception antennas. And
Receiving means for receiving, as a corresponding received wave corresponding to each transmitted wave, the reflected wave reflected by the target from each of the at least two transmitting antennas via the plurality of receiving antennas;
Combining means for obtaining reception results from a plurality of virtual receiving antennas from the plurality of receiving antennas by combining the plurality of corresponding received waves received by the receiving means;
Detecting means for detecting the target based on the reception result obtained by the synthesizing means,
The combining means includes at least two of the plurality of receiving antennas that have received the first corresponding received wave among the plurality of corresponding received waves to be combined and received the first corresponding received wave. Among the plurality of reception antennas that have received the second corresponding reception wave and at least two predetermined number of reception antennas, the same number of reception antennas as the combination reference antennas for combining are determined, and the first The predetermined number of combined reference antennas formed between the predetermined number of combined reference antennas of the corresponding received wave and the predetermined number of combined reference antennas of the second corresponding received wave and capable of phase combining of the corresponding received waves The first corresponding received wave and the second corresponding received wave are combined based on the received wave phase via at least one combined reference antenna pair among the number of combined reference antenna pairs.
Radar device. The combining means, when the received wave intensity of each combined reference antenna included in each combined reference antenna pair exceeds the reference signal intensity in the predetermined number of combined reference antenna pairs, As the antenna pair, the first corresponding received wave and the second corresponding received wave are combined.
The radar apparatus according to claim 1. The combining unit is configured to perform the first correspondence based on the received wave phase via the combined reference antenna pair having the strongest received wave intensity of each combined reference antenna included in the predetermined number of combined reference antenna pairs. Combining the received wave and the second corresponding received wave;
The radar apparatus according to claim 1. The synthesis means includes
Based on the received signal strengths of the predetermined number of combined reference antennas of the first corresponding received wave and the received signal strengths of the predetermined number of combined reference antennas of the second corresponding received wave, A correction phase calculating means for calculating a correction phase for combining the one corresponding received wave and the second corresponding received wave;
The combining unit combines the first corresponding received wave and the second corresponding received wave based on the correction phase calculated by the correction phase calculating unit via the at least one combination reference antenna pair.
The radar apparatus according to claim 1. The synthesis means includes
Determining means for determining whether a signal strength of a combined reference antenna included in the at least one combined reference antenna pair is smaller than a reference signal strength;
When the determination unit determines that the signal strength of the combined reference antenna is smaller than the reference signal strength, one of the combined reference antennas corresponding to the first corresponding received wave among the combined reference antenna pair is received in the plurality of receptions. First estimation means for estimating a reception wave phase of the one combined reference antenna based on reception wave phases of the remaining reception antennas formed by removing from the antenna;
Similarly, when it is determined that the signal strength of the combined reference antenna is smaller than the reference signal strength, the other combined reference antenna corresponding to the second corresponding received wave in the combined reference antenna pair is removed from the plurality of receiving antennas. Second estimation means for estimating the received wave phase of the other combined reference antenna based on the received wave phase of the remaining receiving antenna,
The combining unit calculates a phase difference between the received wave phase estimated by the first estimating unit and the received wave phase estimated by the second estimating unit, and receives the reception signal via the one combined reference antenna pair. Combining the first corresponding received wave and the second corresponding received wave based on the wave phase and the phase difference;
The radar apparatus according to claim 1.

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