JP7346095B2 - radar system - Google Patents

Description

Embodiments of the present invention relate to radar systems.

In a multistatic radar system where the transmitting device and receiving device are located far apart, in order to identify the position of the target to be searched, it is necessary to determine the distance from the transmitting device to the receiving device via the target, and the distance between the transmitting device and the receiving device via the target. Reception angle is required. In order to measure the aforementioned distance, time synchronization between the transmitting device and the receiving device is required. For example, time synchronization between devices is performed by using signals transmitted from GPS (Global Positioning System) satellites. However, in places where signals cannot be received from GPS satellites, time synchronization cannot be performed, and the search for the target may not be possible, or even if it is possible, the accuracy may be significantly degraded.

Merrill I. Skolnik, "Introduction to radar systems," McGRAW-HILL Inc., 1980, pp.428-430 Yoshida, "Revised Radar Technology", Institute of Electronics, Information and Communication Engineers, 1996, pp. 134-135 Yoshida, "Revised Radar Technology", Institute of Electronics, Information and Communication Engineers, 1996, pp. 289-291 Jian Li, Petre Stoica, "MIMO Radar Signal Processing," John Wiley & Sons, Inc., 2009, pp.1-5

The problem to be solved by the present invention is to provide a radar system that can specify the position of a target without performing time synchronization between a transmitting device and a receiving device.

The radar system of the embodiment includes a first transmitter and a receiver. The first transmitting device has a transmitting antenna, a signal combining section, and a transmitting section. The signal combining unit generates a first transmission signal that is transmitted by each of a plurality of transmission beams formed by a transmission antenna and directed in different directions, and that uses a different code sequence for each transmission beam. do. The transmitter transmits a first transmit signal for each transmit beam from the transmit antenna. The receiving device includes an array antenna, a signal separating section, a receiving beam forming section, and a signal processing section. An array antenna has multiple antenna elements. The signal separation unit extracts the first transmission signal from the first reception signal received by each of the plurality of antenna elements using different code sequences. The reception beam forming section is formed by an array antenna , and uses a first reception weight according to a plurality of reception beams having different directivity directions to form each of the plurality of reception beams having different directivity directions for each transmission beam of a different code sequence. generate a receive beam signal. The signal processing unit specifies, for each received beam signal, the pointing direction of the receiving beam that detected the object by CFAR processing, specifies the pointing direction of the transmitting beam from the code sequence, and determines the position of the first transmitting device and the receiving device. , the position of the object that reflected the first transmission signal is specified based on the directional direction of the transmitted beam and the directional direction of the received beam .

FIG. 3 is a diagram illustrating an example arrangement of a transmitting side device and a receiving side device included in the radar system of the first embodiment. FIG. 2 is a diagram illustrating an overview of a process in which the radar system of the first embodiment detects a target. FIG. 2 is a diagram showing an overview of signals transmitted in the radar system of the first embodiment. The figure which shows the example of a structure of the transmitter in 1st Embodiment. The figure which shows the example of a structure of the transmitter-receiver apparatus in 1st Embodiment. FIG. 3 is a diagram showing an example of a coordinate system related to the array antenna in the first embodiment. FIG. 7 is a diagram showing an overview of signals transmitted in a radar system according to a second embodiment. The figure which shows the example of a structure of the transmitter in 2nd Embodiment. FIG. 7 is a diagram illustrating an example of a process in which a frequency division unit generates a modulated signal in the second embodiment. The figure which shows the example of a structure of the transmitting and receiving apparatus in 2nd Embodiment. FIG. 7 is a diagram showing an overview of signals transmitted in a radar system according to a third embodiment. FIG. 7 is a diagram illustrating a configuration example of a transmitting device in a third embodiment. FIG. 7 is a diagram illustrating a configuration example of a transmitting/receiving device in a third embodiment. FIG. 7 is a diagram illustrating an overview of time-division transmission in a radar system according to a second embodiment.

Hereinafter, a radar system according to an embodiment will be described with reference to the drawings. In the following embodiments, components with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate.

(First embodiment)
FIG. 1 is a diagram showing an example of the arrangement of a transmitting side device (TX) and a receiving side device (RX) included in the radar system of the first embodiment. The radar system of the first embodiment is a multistatic system in which transmitter and receiver devices are located separately. Although the example shown in FIG. 1 shows a case where there is one device on the receiving side, there may be two or more devices on the receiving side. A transmitting side device (TX) forms a transmitting multi-beam including a plurality of transmitting beams (T1, T2, . . . , TNt) and transmits a signal toward the observation space. The receiving side device (RX) forms a receiving multi-beam including a plurality of receiving beams (R1, R2,...RNr). A transmitting multi-beam and a receiving multi-beam are formed to cover the observation space. The example shown in FIG. 1 shows a case where transmitting multi-beams and receiving multi-beams are formed in a plane space. However, on each of the transmitting side and the receiving side, a plurality of beams having different pointing directions in the azimuth direction and the elevation direction may be formed so as to cover the three-dimensional observation space.

FIG. 2 is a diagram illustrating an overview of the process by which the radar system of the first embodiment detects a target. By forming the transmitting multi-beam and the receiving multi-beam so as to overlap and cover the observation space, a part of the observation space can be specified by the combination of the transmitting beam and the receiving beam. As shown in Figure 2, the observation space consists of (Nt×Nr) beams (T1, T2, ..., TNt) on the vertical axis and reception beams (R1, R2, ...RNr) on the horizontal axis. is divided into subspaces. The receiving device can identify the subspace where the target is located by identifying the combination of the receiving beam that detected the signal reflected by the target and the transmitting beam that transmitted the signal reflected by the target. In this way, the three-dimensional position of the target is determined based on the positions of the transmitter and receiver devices and the pair of transmit and receive beams.

When specifying the target position using a combination of a transmitting beam and a receiving beam, the target position can be specified without measuring the distance from the transmitting side device to the receiving side device via the target. That is, the target position can be specified without time synchronization between the transmitting and receiving devices. In the radar system of the first embodiment, a transmission signal is generated using a different code sequence for each transmission beam so that a receiving device can identify a plurality of transmission beams.

FIG. 3 is a diagram showing an overview of signals transmitted in the radar system of the first embodiment. In FIG. 3, a transmission signal is shown in a three-dimensional space in which the respective axes of the antenna element number of the array antenna used for transmission, the number of codes used for the transmission beam, and time are combined. The signals transmitted from each of antenna elements #1 to #N in a pulse at a certain time are synthesized (multiplexed) of modulated signals modulated using different code sequences (b1, b2, ..., bNt) for each transmission beam. This is the signal that was sent. That is, in a radar system, transmission signals of a plurality of transmission beams are simultaneously transmitted within the same pulse. In the radar system, such transmission signals are transmitted sequentially. Different code sequences are assigned to the transmission signals of the respective transmission beams, and isolation between the transmission beams is maintained. As such a code sequence, the Barker code described in Non-Patent Document 1 may be used, or other codes may be used.

FIG. 4 is a diagram showing a configuration example of the transmitting device 100 in the first embodiment. The transmitting device 100 is used as the aforementioned transmitting side device (first transmitting device). The transmitting device 100 includes a signal generation section 1, a code modulation section 2, a transmission beam control section 3, a weight control section 4, a signal synthesis section 5, a DAC (Digital-Analog Converter) 6 (6-1, 6-2,..., 6-N), frequency converter 7 (7-1, 7-2,..., 7-N), HPA (High Power Amplifier) 8 (8-1, 8-2) ,...,8-N), and an array antenna having N antenna elements 10 (10-1, 10-2,..., 10-N). N DACs 6, frequency converters 7, and HPAs 8 are provided corresponding to each antenna element 10.

The signal generation section 1 generates a transmission reference signal according to the input transmission beam control signal, and supplies the generated transmission reference signal to the code modulation section 2. The transmission reference signal is, for example, a signal having the frequency, bandwidth, and amplitude indicated by the transmission beam control signal. The code modulation unit 2 performs pulse modulation on the supplied transmission reference signal, and further performs modulation using a code sequence assigned to each of the Nt transmission beams to be formed, thereby generating Nt modulated signals. do. The code modulator 2 supplies the generated Nt modulated signals to the weight controller 4. In addition to pulse modulation and code modulation, the code modulation section 2 may perform frequency modulation on the transmission reference signal. When frequency modulation is performed, the modulation signal becomes a chirp signal.

The transmission beam control unit 3 supplies the complex weights of each antenna element 10 corresponding to the beam directivity directions of each of the Nt transmission beams indicated by the input transmission beam control signal to the weight control unit 4 as transmission weights. The transmission beam control unit 3 may read the complex weight of each antenna element 10 corresponding to the beam directivity direction from a table that stores the complex weight of each antenna element 10 for each beam directivity direction. The complex weight of each antenna element 10 is determined by the combination of the amplitude weight for sidelobe reduction and the phase weight for beam scanning. The direction of each of the transmission beams forming the transmission multi-beam is determined so that the plurality of transmission beams covers the observation space.

The weight control unit 4 multiplies each of the Nt modulated signals supplied from the code modulation unit 2 by the complex weight of the transmission beam corresponding to the code sequence used when generating the modulated signal, and adjusts each of the antenna elements 10 accordingly. Calculate the signal transmitted by That is, the weight control unit 4 calculates signals corresponding to the N antenna elements 10 for each of the Nt transmission beams. The weight control unit 4 supplies the calculated (N×Nt) signals to the signal synthesis unit 5. The signal combining unit 5 combines the (N×Nt) signals supplied from the weight control unit 4 with signals corresponding to each of the N antenna elements 10, and generates N combined signals. The signal combining unit 5 supplies combined signals corresponding to each of the N antenna elements to the DAC 6 corresponding to each antenna element.

Each of the DACs 6 converts the synthesized signal supplied from the signal synthesizer 5 from a digital signal to an analog signal, and supplies the intermediate frequency signal obtained by the conversion to the frequency converter 7. Each of the frequency converters 7 converts the supplied intermediate frequency signal into a high frequency signal, and supplies the high frequency signal to the HPA 8. Each HPA 8 amplifies the supplied high frequency signal with high output. Each high frequency signal amplified by the HPA 8 is supplied to the antenna element 10 corresponding to the HPA 8, and is sent out from the antenna element 10 as a transmission signal. In this way, the DAC 6, the frequency converter 7, and the HPA 8 operate as a transmitter that transmits high-frequency signals. Through the above operations, the transmitting device 100 simultaneously transmits high frequency signals generated for each transmission beam from an array antenna serving as a transmitting antenna.

FIG. 5 is a diagram showing a configuration example of the transmitting/receiving device 200 in the first embodiment. The transmitting/receiving device 200 is used as the aforementioned receiving device. The transmitter/receiver 200 includes a signal generator 1, a code modulator 2, a transmit beam controller 3, a weight controller 4, a signal synthesizer 5, a DAC 6 (6-1, 6-2,..., 6-N), and a frequency converter. Container 7 (7-1, 7-2,..., 7-N), HPA 8 (8-1, 8-2,..., 8-N), Circulator 9 (9-1, 9-2,..., 9- N), an array antenna having N antenna elements 10 (10-1, 10-2,..., 10-N), and an LNA (Low Noise Amplifier) 11 (11-1, 11-2,... , 11-N), frequency converter 12 (12-1, 12-2,..., 12-N), ADC (Analog-Digital Converter) 13 (13-1, 13-2,... , 13-N), a signal separation section 14, a reception beam control section 15, a reception beam formation section 16, and a signal processing section 17.

N DACs 6, frequency converters 7, HPAs 8, circulators 9, LNAs 11, frequency converters 12, and ADCs 13 are provided corresponding to each antenna element 10. The signal generation section 1, code modulation section 2, transmission beam control section 3, weight control section 4, signal synthesis section 5, DAC 6, frequency converter 7, and HPA 8 are the same as those included in the above-mentioned transmitting device 100. . Each of the high frequency signals amplified by the HPA 8 is supplied to the antenna element 10 via the circulator 9 corresponding to the HPA 8, and is sent out from the antenna element 10 as a second transmission signal. Also in the transmitter/receiver 200, high frequency signals generated for each transmission beam are simultaneously transmitted from the array antenna.

Each of the antenna elements 10 supplies the received signal (first received signal) to the corresponding LNA 11 via the circulator 9 . When an object as a target to be searched is located in the observation space, the received signal includes a reflected signal in which a high frequency signal is reflected at the target. Each of the LNAs 11 performs low-noise amplification on the supplied received signal and supplies the amplified received signal to the frequency converter 12 . Each of the frequency converters 12 converts the frequency of the supplied received signal to an intermediate frequency, and supplies the intermediate frequency signal obtained by the conversion to the ADC 13 . Each ADC 13 converts the intermediate frequency signal from an analog signal to a digital signal, and supplies the obtained digital signal to the signal separation unit 14 .

The signal separation unit 14 performs correlation processing on each of the N digital signals supplied from the ADC 13 corresponding to each antenna element 10 for each code sequence corresponding to each of the Nt transmission beams. When a digital signal includes a high-frequency signal component, the high-frequency signal component included in the digital signal is extracted by correlation processing with a code sequence assigned to a transmission beam when transmitting the high-frequency signal. That is, the high frequency signal components included in the digital signal are separated by correlation processing with the code sequence. Even when the digital signal includes high frequency signal components corresponding to a plurality of transmission beams, the respective high frequency components are separated by correlation processing. The signal separation section 14 supplies (N×Nt) separated signals obtained by correlation processing for each of the Nt code sequences to the digital signals corresponding to each of the N antenna elements 10 to the reception beam forming section 16. The signal separation unit 14 may store in advance Nt code sequences used for correlation processing.

The reception beam control unit 15 supplies the complex weight of each of the Nr reception beams that form the reception multi-beam indicated by the reception beam control signal to the reception beam formation unit 16 as a first reception weight. . The complex weight of each antenna element 10 is determined by the combination of the amplitude weight for sidelobe reduction and the phase weight for beam scanning. The direction of each of the receiving beams forming the receiving multi-beam is determined so that the plurality of receiving beams covers the observation space. The reception beam forming unit 16 forms a reception beam signal for each of the N separated signals extracted with the same code sequence, using the complex weight of each supplied reception beam. That is, the reception beam forming section 16 forms Nr reception beam signals for each high frequency signal transmitted using each of the Nt transmission beams. The reception beam forming section 16 supplies the formed (Nt×Nr) reception beam signals to the signal processing section 17 .

The signal processing unit 17 performs suppression of unnecessary waves included in the beam signal and target extraction processing for each of the (Nt×Nr) received beam signals supplied. For example, the signal processing unit 17 uses CFAR processing to determine the presence or absence of a target for each received beam signal. Based on the combination of the code sequence used to extract the separated signal used to form the target-detected receive beam signal and the receive beam corresponding to the target-detected receive beam signal, the signal processing unit 17 performs the following: Locate the target. The signal processing unit 17 identifies the directional direction of the transmitting beam from the code sequence, and determines the area where the target is located based on the positions of the transmitting device 100 and its own device, the directional direction of the transmitting beam, and the directional direction of the receiving beam. Identify. The signal processing unit 17 outputs target information indicating the number of detected targets and the position of each target.

Note that the signal processing unit 17 may store in advance the position of the transmitter 100 and the directivity direction of the transmit beam for each code sequence. Alternatively, the transmitting device 100 may transmit the position of the transmitting device 100 and the directivity direction of the transmission beam corresponding to each code sequence in a high-frequency signal, and notify the transmitting/receiving device 200. When the position and pointing direction are notified from the transmitting device 100, the signal processing unit 17 may acquire the position of the transmitting device 100 and the pointing direction of the transmission beam corresponding to each code sequence from the received signal.

In the transmitting/receiving device 200, when the target position is specified by the combination of the transmitting beam and the receiving beam, the transmitting beam control unit 3 controls each antenna element 10 corresponding to the transmitting beam directed toward the target position based on the target information. The complex weight of is supplied to the weight control unit 4 as a second transmission weight. In addition to the complex weights corresponding to the transmission beams directed to the target position, the transmission beam control unit 3 may supply the weight control unit 4 with complex weights corresponding to the transmission beams directed to the vicinity of the target position. . The transmission beam directed to the vicinity of the target position is, for example, a transmission beam directed to a subspace adjacent to the subspace in which the target is detected. By supplying the complex weight corresponding to the transmission beam directed to the target position and its vicinity from the transmission beam control unit 3 to the weight control unit 4, transmission from the transmitting/receiving device 200 with the pointing direction directed toward the target and its vicinity. A high frequency signal (second transmission signal) is transmitted in the beam.

When a high-frequency signal is transmitted from the transmitting/receiving device 200 using a transmission beam directed toward the target and its vicinity, the reception beam control unit 15 adjusts the complex weight corresponding to the reception beam directed toward the target position and its vicinity. is supplied to the reception beam forming section 16 as a second reception weight. The reception beam forming unit 16 generates a reception beam signal (second reception beam signal) from the reception signal (second reception signal) received by each antenna element 10 using the supplied complex weight. The received beam signal is supplied to the signal processing section 17. The signal processing unit 17 identifies the target position with higher accuracy through monostatic observation using reception beam signals corresponding to reception beams directed toward the target position and its vicinity.

When observing a target using a transmitting beam directed toward the target and its vicinity, the area where the target is located has already been identified, so the target sensitivity can be increased by lowering the CFAR processing threshold in that area. Can be made high. For example, as the threshold value of the CFAR processing used at this time, a value smaller than the threshold value used when the reflected signal of the high frequency signal (first transmission signal) transmitted from the transmitting device 100 is received can be used. Further, the code modulation unit 2 may determine the pulse repetition interval of the high frequency signal (second transmission signal) to be transmitted according to the distance to the already specified target position. When multiple targets are detected, the time required for transmission to each target can be allocated more efficiently, and the accuracy of observation, search, tracking, etc. of each target can be improved.

In addition, if the accuracy of the target position to be detected is sufficient for the target position specified by the combination of the transmitting beam and the receiving beam, the transmitting beam and the receiving beam directed toward the target and its vicinity are used. Processing may be omitted. In this case, the receiving side device in the radar system of the first embodiment does not need to have the transmission-related functions of the transmitting/receiving device 200 shown in FIG. 5 . That is, as a receiving side device, an array antenna having N antenna elements 10 (10-1, 10-2, ..., 10-N), and an LNA 11 (11-1, 11-2, ..., 11-N) are used. , frequency converter 12 (12-1, 12-2,..., 12-N), ADC 13 (13-1, 13-2,..., 13-N), signal separation section 14, reception beam control section 15, reception A receiving device including a beam forming section 16 and a signal processing section 17 may be used.

Further, instead of the transmitting/receiving device 200, the above-described receiving device and the transmitting device 100 shown in FIG. 4 may be used. When two devices are used in place of the transmitting/receiving device 200, the receiving device and the transmitting device 100 as the second transmitting device are placed close to each other, and based on the target position specified by the combination of the transmitting beam and the receiving beam, , the target position may be identified with higher accuracy.

The processing related to transmission performed in the transmitting device 100 and the transmitting/receiving device 200 will be formulated below. FIG. 6 is a diagram showing an example of a coordinate system related to the array antenna in the first embodiment. A three-dimensional coordinate system of XYZ axes is set with the phase center of the array antenna as the origin. In the coordinate system shown in FIG. 6, a signal Xen (antenna element number: n=1, 2, . . . , N) transmitted from each antenna element 10 included in the array antenna is given by equation (1).

式（１）において、各アンテナ素子１０の信号Ｘｅｎに含まれ、Ｎｔ個の送信ビームそれぞれに対応する成分Ｘｎｍ、すなわちウェイト制御部４が出力する信号は、式（２）で与えられる。

In equation (1), the component Xnm included in the signal Xen of each antenna element 10 and corresponding to each of the Nt transmission beams, that is, the signal output by the weight control unit 4 is given by equation (2).

式（２）において、ｍ（＝１，２，…，Ｎｔ）は送信ビームの番号を示し、ｆは高周波信号のキャリア周波数を示し、ｔはパルス幅内における時間を示す。ｃｏｄｅｍは、ｍ番目の送信ビームに割り当てられた符号系列を示す。符号系列ｃｏｄｅｍの符号長は、符号系列ｃｏｄｅｍで変調された信号のパルス幅と一致する。［ｘｎ，ｙｎ，ｚｎ］は、ｎ番目のアンテナ素子１０の位置座標を示す。位置座標の基準位置は、アレイアンテナの位相中心である。式（２）における［ｋｘ，ｋｙ，ｋｚ］は、式（３）で与えられる。

In equation (2), m (=1, 2, . . . , Nt) indicates the number of the transmission beam, f indicates the carrier frequency of the high frequency signal, and t indicates the time within the pulse width. codem indicates a code sequence assigned to the m-th transmission beam. The code length of the code sequence codem matches the pulse width of the signal modulated by the code sequence codem. [xn, yn, zn] indicates the position coordinates of the n-th antenna element 10. The reference position of the position coordinates is the phase center of the array antenna. [kx, ky, kz] in equation (2) is given by equation (3).

式（３）において、λは高周波信号の波長を示し、ＡＺ、ＥＬはアレイアンテナから見た方位角（Azimuth）方向、仰角（Elevation）方向ぞれぞれの角度を示す。

In Equation (3), λ represents the wavelength of the high-frequency signal, and AZ and EL represent the angles in the azimuth direction and the elevation direction as seen from the array antenna.

In Equation (2), Wanm represents the sidelobe reduction weight for the n-th antenna element in the m-th transmission beam. Wpnm indicates a complex weight that controls the beam pointing direction for the n-th antenna element in the m-th transmission beam. Weights for sidelobe reduction include the Taylor distribution described in Non-Patent Document 2. The complex weight Wpnm that controls the beam pointing direction can be expressed by equation (4).

式（４）における［ｋｐｘｍ，ｋｐｙｍ，ｋｐｚｍ］は、式（５）で与えられる。

[kpxm, kpym, kpzm] in equation (4) is given by equation (5).

式（５）において、ＡＺｍ、ＥＬｍは、アレイアンテナの位相中心から見たｍ番目の送信ビームの方位角（Azimuth）方向、仰角（Elevation）方向それぞれのビーム指向角を示す。

In Equation (5), AZm and ELm indicate beam directivity angles in the azimuth direction and the elevation direction of the m-th transmission beam as viewed from the phase center of the array antenna.

As shown in equation (1), each antenna element 10 produces a signal in which the signals of the respective transmission beams are superimposed (combined). Isolation between superimposed signals is maintained by a code sequence (modulation code).

A transmission beam signal (high frequency signal) Ym sent out as a transmission multi-beam is expressed by equation (6), which is obtained by adding and combining the signals Xen of each antenna element 10 given by equation (1).

Next, processing related to reception performed in the transmitting/receiving device 200 will be formulated. The signal Xrnm received by each antenna element 10 is expressed by equation (7).

式（７）において、ｎ（＝１，２，…，Ｎ）とｍ（＝１，２，…，Ｎｒ）とは、アンテナ素子１０の番号と受信ビームの番号とをそれぞれ示す。なお、送信と受信とに用いるアンテナ素子１０の数を同じＮとしているが、送信に用いるアンテナ素子１０の数と受信に用いるアンテナ素子１０の数とが異なっていてもよい。Ａｔｇｔは目標で反射した反射信号の振幅を示し、ｆは高周波信号のキャリア周波数を示し、ｆｔｇｔは反射信号のドップラ周波数を示す。ｃｏｄｅｍは、ｍ番目の送信ビームに割り当てられた符号系列を示す。［ｘｎ，ｙｎ，ｚｎ］は、ｎ番目のアンテナ素子１０の位置座標を示す。式（７）における［ｋｘ，ｋｙ，ｋｚ］は、式（８）で与えられる。

In equation (7), n (=1, 2, . . . , N) and m (= 1, 2, . . . , Nr) indicate the number of the antenna element 10 and the number of the receiving beam, respectively. Note that although the number of antenna elements 10 used for transmission and reception is the same N, the number of antenna elements 10 used for transmission and the number of antenna elements 10 used for reception may be different. Atgt indicates the amplitude of the reflected signal reflected at the target, f indicates the carrier frequency of the high frequency signal, and ftgt indicates the Doppler frequency of the reflected signal. codem indicates a code sequence assigned to the m-th transmission beam. [xn, yn, zn] indicates the position coordinates of the n-th antenna element 10. [kx, ky, kz] in equation (7) is given by equation (8).

式（８）において、λは、反射信号の波長を示し、ＡＺ、ＥＬは、アレイアンテナの位相中心から見た方位角（Azimuth）方向、仰角（Elevation）方向それぞれの観測角を示す。

In Equation (8), λ indicates the wavelength of the reflected signal, and AZ and EL indicate the observation angles in the azimuth direction and the elevation direction, respectively, as viewed from the phase center of the array antenna.

In order to simplify the explanation, the case where there is one target is shown, but if there are multiple targets, the signal Xrnm shown by equation (7) is added for the number of targets. The signal separation unit 14 separates the reflected signal from the received signal Xrnm given by Equation (7) using the carrier frequency and code sequence, and obtains the separated signal Xrnm_div given by Equation (9).

The reception beam forming unit 16 forms a reception beam signal Yrm corresponding to each reception beam by calculation using the DBF of equation (10) (Non-Patent Document 3).

式（１０）における、Ｗａｎｍはサイドローブ低減用のウェイトを示し、Ｗｐｎｍは受信ビームのビーム指向方向制御用の複素ウェイトを示す。Ｗｐｎｍは、式（１１）で表現できる。

In Equation (10), Wanm indicates a weight for sidelobe reduction, and Wpnm indicates a complex weight for controlling the beam pointing direction of the received beam. Wpnm can be expressed by equation (11).

式（１１）における［ｋｐｘｍ，ｋｐｙｍ，ｋｐｚｍ］は、式（１２）で与えられる。

[kpxm, kpym, kpzm] in equation (11) is given by equation (12).

式（１２）において、ＡＺｍ、ＥＬｍは、アレイアンテナの位相中心から見たｍ番目の受信ビームの方位角（Azimuth）方向、仰角（Elevation）方向それぞれのビーム指向角を示す。

In Equation (12), AZm and ELm indicate beam directivity angles in the azimuth direction and the elevation direction of the m-th reception beam as seen from the phase center of the array antenna.

The signal processing unit 17 detects the target by signal processing using the received beam signal obtained by equation (10). The target is detected by signal processing of the received beam signal, and a code sequence used to extract the separated signal used to form the received beam signal in which the target was detected is obtained. The signal processing unit 17 targets a part of the observation area using a pair of a transmission beam (T1 to TNt) corresponding to the obtained code sequence and a reception beam (R1 to RNr) corresponding to the reception beam signal. It can be identified as the area where is located. If the purpose is to obtain the approximate position of a target, target information indicating the identified area is output. Further, when acquiring a highly accurate target position, the transmitting/receiving device 200 acquires the target position by performing the above-mentioned monostatic observation, and outputs target information indicating the acquired target position.

According to the radar system of the first embodiment, the directivity of the transmitting beam specified by the code sequence used when the high-frequency signal component (first transmitting signal) was extracted from the received signal, and the receiving beam. The area where the target is located can be specified by a combination of pointing directions, and the position of the target can be specified without time synchronization between the transmitting device and the receiving device. By the way, in a multistatic radar system that combines a transmitting fan beam and a receiving multibeam, the direction of the target as seen from the receiving side can only be specified. On the other hand, the radar system of the first embodiment can specify the target position and can also obtain the target position with higher accuracy.

The radar system of the first embodiment forms a transmission multi-beam and a reception multi-beam to detect a target in an observation space. Processing that combines transmitting multi-beams and receiving multi-beams can be said to be a form of MIMO (Multiple Input Multiple Output) (Non-Patent Document 4). Generally, MIMO transmission and reception processing is performed at the antenna element level (Element-Space (ES)). On the other hand, it can be said that the radar system in the first embodiment performs transmission and reception processing at the beam level (Beam-Space (BS)).

In beam space (BS) type MIMO, the number of transmission beams to be formed matches the number of code sequences used to generate transmission signals. On the other hand, in element space (ES) type MIMO, even if the observation space is limited by reducing the number of transmission beams to be formed, the number of code sequences used cannot be reduced. BS-type MIMO has the advantage that by limiting the observation space and reducing the number of transmission beams, the number of code sequences required to generate transmission signals can be reduced, and the calculation load in transmission processing can be reduced.

(Second embodiment)
In the first embodiment, isolation between transmission beams is ensured by using different code sequences, but code modulation using code sequences may not provide sufficient isolation. Therefore, in the second embodiment, a radar system will be described in which isolation between transmission beams is ensured by assigning different frequencies to the transmission beams.

FIG. 7 is a diagram showing an overview of signals transmitted in the radar system of the second embodiment. In FIG. 7, the transmitted signal is shown in three dimensions, which is a combination of the antenna element number of the array antenna, frequency, and time axes. The signals transmitted from each of the antenna elements #1 to #N in a pulse at a certain time are signals in which signals of different frequency bands (f1, f2, . . . , fNt) assigned to each transmission beam are combined. That is, in the radar system of the second embodiment, a plurality of transmission beams having different frequency bands are simultaneously transmitted within the same pulse. In the radar system of the second embodiment, such transmission signals are transmitted sequentially.

FIG. 8 is a diagram illustrating a configuration example of a transmitting device 100A in the second embodiment. The transmitting device 100A is used as a transmitting device in a radar system. The transmitter 100A includes a signal generator 1, a frequency divider 2a, a transmit beam controller 3, a weight controller 4, a signal combiner 5, a DAC 6 (6-1, 6-2,..., 6-N), and a frequency converter. HPA 8 (8-1, 8-2, ..., 8-N), and N antenna elements 10 (10-1, 10-2) , ..., 10-N). A transmitting device 100A in the second embodiment differs from the transmitting device 100 in the first embodiment in that it includes a frequency division section 2a instead of the code modulating section 2.

In order to ensure isolation between transmission beams, the frequency division section 2a divides the transmission reference signal into different frequency bands assigned to each transmission beam, and generates Nt divided signals. FIG. 9 is a diagram illustrating an example of a process in which the frequency division section 2a generates a modulated signal in the second embodiment. The frequency division section 2a performs FFT on the transmission reference signal supplied from the signal generation section 1, and converts the transmission reference signal into a signal on the frequency axis. The frequency dividing unit 2a generates Nt divided band signals by dividing the signal on the frequency axis into divided bands assigned to each of the Nt transmission beams. The frequency dividing unit 2a performs inverse FFT after zero-filling the components of bands other than the divided bands in each divided band signal to generate a time-axis signal. The frequency division unit 2a generates a modulated signal by performing pulse modulation on Nt time-axis signals. The frequency division section 2 a supplies the generated Nt modulation signals to the weight control section 4 . The frequency division section 2a may further perform frequency modulation and generate a chirp signal as a modulation signal.

FIG. 10 is a diagram showing a configuration example of a transmitting/receiving device 200A in the second embodiment. The transmitting/receiving device 200A is used as a receiving device in a radar system. The transmitter/receiver 200A includes a signal generator 1, a frequency divider 2a, a transmit beam controller 3, a weight controller 4, a signal combiner 5, a DAC 6 (6-1, 6-2,..., 6-N), and a frequency converter. Container 7 (7-1, 7-2,..., 7-N), HPA 8 (8-1, 8-2,..., 8-N), Circulator 9 (9-1, 9-2,..., 9- N), array antenna having N antenna elements 10 (10-1, 10-2,..., 10-N), LNA 11 (11-1, 11-2,..., 11-N), frequency converter 12 (12-1, 12-2,..., 12-N), ADC 13 (13-1, 13-2,..., 13-N), frequency division section 14a, reception beam control section 15, reception beam forming section 16, and a signal processing section 17. A transmitting/receiving device 200A in the second embodiment differs from the transmitting/receiving device 200 in the first embodiment in that it includes a frequency dividing section 2a and a frequency dividing section 14a instead of the code modulating section 2 and signal separating section 14.

The frequency dividing unit 14a frequency-separates each of the N digital signals supplied from the ADC 13 corresponding to each antenna element 10 into frequency bands assigned to each transmission beam, and generates (N×Nt) divided signals. generate. The frequency division section 14a supplies the generated (N×Nt) divided signals to the reception beam forming section 16. The reception beam forming section 16 uses the complex weights of each reception beam supplied from the reception beam control section 15 to form reception beam signals for each frequency band assigned to the transmission beam. That is, the reception beam forming section 16 forms Nr reception beam signals for each frequency band assigned to the transmission beam. The reception beam forming section 16 supplies the formed (Nt×Nr) reception beam signals to the signal processing section 17 .

Next, the processing related to transmission performed in the transmitting device 100A and the transmitting/receiving device 200A will be formulated below. A signal Xen (antenna element number: n=1, 2, . . . , N) transmitted from each antenna element 10 of the array antenna is given by equation (13).

式（１３）において、各アンテナ素子１０の信号Ｘｅｎに含まれ、Ｎｔ個の送信ビームそれぞれに対応する成分Ｘｎｍ、すなわちウェイト制御部４が出力する信号は、式（１４）で与えられる。

In equation (13), the component Xnm included in the signal Xen of each antenna element 10 and corresponding to each of the Nt transmission beams, that is, the signal output by the weight control section 4 is given by equation (14).

式（１４）において、ｍ（＝１，２，…，Ｎｔ）は送信ビームの番号を示し、ｆは高周波信号のキャリア周波数を示し、ｔはパルス幅内における時間を示す。Δｔは分割帯域の周波数を示し、［ｘｎ，ｙｎ，ｚｎ］はｎ番目のアンテナ素子１０の位置座標を示す。位置座標の基準位置は、アレイアンテナの位相中心である。

In equation (14), m (=1, 2, . . . , Nt) indicates the number of the transmission beam, f indicates the carrier frequency of the high frequency signal, and t indicates the time within the pulse width. Δt indicates the frequency of the divided band, and [xn, yn, zn] indicates the position coordinates of the n-th antenna element 10. The reference position of the position coordinates is the phase center of the array antenna.

[kx, ky, kz] in equation (14) is given by equation (3) above. Furthermore, in Equation (14), Wanm represents a sidelobe reduction weight for the n-th antenna element in the m-th transmission beam. Wpnm indicates a complex weight that controls the beam pointing direction for the n-th antenna element in the m-th transmission beam, and can be expressed by the above equation (4).

Δfm (m=1, 2, . . . , Nt) in Equation (14) corresponds to the frequency of the divided band assigned to each transmission beam. As shown in equation (13), each antenna element 10 transmits a signal in which signals corresponding to each transmission beam are superimposed (combined). In the radar system of the second embodiment, isolation between transmission beams is ensured by frequency division.

Next, processing related to reception performed in the transmitting/receiving device 200 will be formulated. The signal Xrnm received by each antenna element 10 is expressed by equation (15).

式（１５）において、ｎ（＝１，２，…，Ｎ）とｍ（＝１，２，…，Ｎｒ）とは、アンテナ素子１０の番号と受信ビームの番号とをそれぞれ示す。Ａｔｇｔは、目標で反射した反射信号の振幅を示し、ｆは高周波信号のキャリア周波数を示し、ｆｔｇｔは反射信号のドップラ周波数を示す。Δｔは分割帯域の周波数を示し、［ｘｎ，ｙｎ，ｚｎ］はｎ番目のアンテナ素子１０の位置座標を示す。式（１５）における［ｋｘ，ｋｙ，ｋｚ］は、前述の式（８）で与えられる。

In equation (15), n (=1, 2, . . . , N) and m (= 1, 2, . . . , Nr) indicate the number of the antenna element 10 and the number of the receiving beam, respectively. Atgt indicates the amplitude of the reflected signal reflected at the target, f indicates the carrier frequency of the high frequency signal, and ftgt indicates the Doppler frequency of the reflected signal. Δt indicates the frequency of the divided band, and [xn, yn, zn] indicates the position coordinates of the n-th antenna element 10. [kx, ky, kz] in equation (15) is given by equation (8) above.

To simplify the explanation, the case where there is one target is shown, but if there are multiple targets, the signal Xrnm shown by equation (15) is added for the number of targets. The frequency division unit 14a performs frequency separation of the reflected signal using the carrier frequency and each division band Δfm for the received signal Xrnm given by Equation (15), and obtains the divided signal Xrnm_div given by Equation (16). .

The reception beam forming unit 16 forms a reception beam signal Yrm corresponding to each reception beam by calculation using the DBF of equation (17).

式（１７）における［ｋｐｘｍ，ｋｐｙｍ，ｋｐｚｍ］は、前述の式（１２）で与えられる。

[kpxm, kpym, kpzm] in equation (17) is given by equation (12) above.

The signal processing unit 17 detects the target by signal processing using the received beam signal obtained by equation (17). A target is detected by signal processing of the received beam signal, and the frequency of the received beam signal at which the target is detected is obtained. The signal processing unit 17 targets a part of the observation area using a pair of a transmission beam (T1 to TNt) corresponding to the obtained frequency and a reception beam (R1 to RNr) corresponding to a reception beam signal. It can be identified as the area where it is located. If the purpose is to obtain the approximate position of a target, target information indicating the identified area is output. Further, when acquiring a highly accurate target position, the transmitting/receiving device 200A acquires the target position by performing the monostatic observation described in the first embodiment, and target information indicating the acquired target position. Output.

According to the radar system of the second embodiment, the directivity of the transmission beam specified by the frequency of the high-frequency signal component (first transmission signal) included in the reception beam signal, and the reception beam containing the high-frequency signal component The area where the target is located can be specified by a combination of the pointing direction and the pointing direction, and the target position can be specified without time synchronization between the transmitting device and the receiving device.

(Third embodiment)
In the first and second embodiments, the transmitting devices 100, 100A and the transmitting/receiving devices 200, 200A, which simultaneously form and transmit multiple transmission beams, have been described. In the third embodiment, a different method from the first and second embodiments will be described as a method for forming a transmission beam. In the third embodiment, a plurality of transmission beams covering the observation space are formed in a time-division manner. That is, isolation between transmission beams is ensured by a combination of code sequence or frequency division and time division.

FIG. 11 is a diagram showing an overview of signals transmitted in the radar system of the third embodiment. In FIG. 11, a transmission signal is shown in a three-dimensional space that combines the antenna element number of the array antenna, amplitude, and time axes. The signals transmitted from each of antenna elements #1 to #N in a pulse at a certain time are generated by time-division of the pulse and subpulses corresponding to each transmission beam (T1, T2, ..., TNt) are converted into code sequences (b1, b2,..., TNt). . In the radar system of the third embodiment, such transmission signals are sequentially transmitted.

FIG. 12 is a diagram illustrating a configuration example of a transmitting device 100B in the third embodiment. The transmitting device 100B is used as a transmitting device in a radar system. The transmitter 100B includes a signal generator 1, a code modulator 2b, a transmit beam controller 3, a weight controller 4, a signal combiner 5, a DAC 6 (6-1, 6-2,..., 6-N), and a frequency converter. HPA 8 (8-1, 8-2, ..., 8-N), and N antenna elements 10 (10-1, 10-2) , ..., 10-N). A transmitter 100B in the third embodiment differs from the transmitter 100 in the first embodiment in that it includes a code modulator 2b instead of the code modulator 2.

The code modulation section 2b divides the transmission reference signal supplied from the signal generation section 1 into subpulses corresponding to each transmission beam, and performs pulse modulation on each subpulse. The code modulation unit 2b modulates the pulse-modulated subpulses using code sequences assigned to each of the Nt transmission beams to be formed, thereby generating Nt modulated signals. The code modulator 2 sequentially supplies the generated Nt modulated signals to the weight controller 4. In addition to pulse modulation and code modulation, the code modulation section 2b may perform frequency modulation on each sub-pulse. When frequency modulation is performed, the modulation signal becomes a chirp signal. The code modulation section 2b sequentially supplies Nt modulated signals to the weight control section 4, so that transmission of high-frequency signals by each transmission beam is performed sequentially in a time-division manner.

FIG. 13 is a diagram showing a configuration example of a transmitting/receiving device 200B in the third embodiment. The transmitter/receiver 200B includes a signal generator 1, a code modulator 2b, a transmit beam controller 3, a weight controller 4, a signal synthesizer 5, a DAC 6 (6-1, 6-2,..., 6-N), and a frequency converter. Container 7 (7-1, 7-2,..., 7-N), HPA 8 (8-1, 8-2,..., 8-N), Circulator 9 (9-1, 9-2,..., 9- N), array antenna having N antenna elements 10 (10-1, 10-2,..., 10-N), LNA 11 (11-1, 11-2,..., 11-N), frequency converter 12 (12-1, 12-2,..., 12-N), ADC 13 (13-1, 13-2,..., 13-N), signal separation section 14, reception beam control section 15, reception beam forming section 16, and a signal processing section 17. A transmitting/receiving device 200B in the third embodiment differs from the transmitting/receiving device 200 in the first embodiment in that it includes a code modulating section 2b instead of the code modulating section 2.

The operation of detecting a target and identifying the three-dimensional position in the third embodiment is the same as the operation in the first embodiment, so a description thereof will be omitted. According to the radar system of the third embodiment, if the width of one pulse can be made longer, a large number of transmission beams can be formed in a time-division manner, and isolation between transmission pulses can be kept high. In addition, since the radar system of the third embodiment does not require a circuit required for forming a transmission multi-beam, it is possible to suppress an increase in the circuit scale of the circuit related to transmission, and to maintain communication between the devices on the transmitting side and the receiving side. Target position can be determined without time synchronization.

12 and 13 show configuration examples of a transmitting device 100B and a transmitting/receiving device 200B that time-divisionally transmit high-frequency signals generated using different code sequences for each transmission beam. Also in the radar system in the second embodiment, the transmitting device 100A and the transmitting/receiving device 200A may be changed so that high frequency signals generated using different frequencies for each transmission beam are transmitted in a time-division manner. When time-division transmission is performed for each transmission beam, the frequency division section 2a sequentially supplies Nt modulated signals generated from the transmission reference signal to the weight control section 4, thereby allowing the transmission of high-frequency signals by each transmission beam. It is done sequentially in time division.

FIG. 14 is a diagram illustrating an overview of time-division transmission in the radar system of the second embodiment. In FIG. 14, the transmitted signal is shown in a three-dimensional space that combines the antenna element number of the array antenna, amplitude, and time axes. Signals transmitted from each of antenna elements #1 to #N in a pulse at a certain time have different frequency bands (f1, f2, ..., fNt) assigned to each transmission beam (T1, T2, ..., TNt). This can be obtained by dividing the frequency into sub-pulses, performing pulse modulation on each sub-pulse, and forming a transmit beam for each sub-pulse using the complex weight for transmit beam forming used in equation (2) or equation (14). It will be done.

(Modified example)
Although the configuration of the radar system in each embodiment has been described, the following changes may be made. In the transmitting/receiving devices 200 and 200B of the first and third embodiments, after the signal separation unit 14 extracts components of high frequency signals (transmission signals) from N digital signals supplied from the ADC 13, the reception beam The configuration in which the forming section 16 forms a reception beam signal has been described. However, the order of operation of the signal separation section 14 and the reception beam forming section 16 may be changed. Specifically, the reception beam forming unit 16 generates a reception beam signal corresponding to each reception beam from the N digital signals supplied from the ADC 13, and the signal separation unit 14 generates a code for each reception beam signal. Correlation processing with the sequence may be performed to extract the component of the high frequency signal (first transmission signal) included in each received beam signal.

Further, in the transmitting/receiving device 200A of the second embodiment as well, the order of operation of the frequency dividing section 14a and the receiving beam forming section 16 may be changed. Specifically, the reception beam forming section 16 generates a reception beam signal corresponding to each reception beam from the N digital signals supplied from the ADC 13, and the frequency division section 14a divides each reception beam signal. By dividing into divided signals for each band, the components of the high frequency signal (first transmission signal) included in each received beam signal may be extracted.

Furthermore, in the radar systems of the first to third embodiments, the configuration example in which the transmitting devices 100, 100A, and 100B are used as the transmitting side devices has been described, but the transmitting and receiving devices 200, 200A, and 200B are used as the transmitting side devices. It's okay.

Further, although the configuration has been described in which the transmitting devices 100, 100A, and 100B in the radar systems of the first to third embodiments are equipped with an array antenna as a transmitting antenna, the transmitting devices 100, 100A, and 100B are capable of forming a transmitting beam, and are also capable of forming a transmitting beam. The antenna may be provided as a transmitting antenna instead of the array antenna. For example, a lens antenna using a dielectric lens, a horn antenna, or a parabolic antenna for each transmission beam may be provided, or a mechanical beam scanning antenna such as a Luneberg lens, Foster scanner, or Eagle scanner antenna may be provided. .

The transmitting device and the transmitting/receiving device in the above embodiments include a CPU (Central Processing Unit), a memory, an auxiliary storage device, etc. connected via a bus, and the CPU executes a program to generate a transmission reference signal and to generate a transmission reference signal. Processing to generate a composite signal from the signals and processing to generate a reception beam signal from the digital signal supplied from the ADC 13 may be performed. The CPU may perform some or all of the operations in the transmitting device and some or all of the operations in the transmitting/receiving device by executing a program stored in the auxiliary storage device. Further, all or part of the operations in the transmitting device and the transmitting/receiving device may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). . The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is a non-temporary storage medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or other portable medium, or a hard disk or other storage device built into a computer system. The program may be transmitted via a telecommunications line.

According to at least one embodiment described above, the code sequence used when the high-frequency signal component (first transmission signal) is extracted and the received beam signal corresponding to the received beam signal from which the high-frequency signal component is extracted. By having a signal processing unit that identifies the position of the object that reflected the high-frequency signal based on the combination with the beam, the target can be determined based on the combination of the transmitting beam direction specified by the code sequence and the receiving beam and the pointing direction. It is possible to specify the area where the target is located, and the position of the target can be specified without time synchronization between the transmitting device and the receiving device.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 1... Signal generation part, 2, 2b... Code modulation part, 2a... Frequency division part, 3... Transmission beam control part, 4... Weight control part, 5... Signal synthesis part, 6... DAC, 7... Frequency converter, 8 ... HAP, 9... Circulator, 10... Antenna element, 11... LNA, 12... Frequency converter, 13... ADC, 14... Signal separation section, 14a... Frequency division section, 15... Reception beam control section, 16... Reception beam formation Unit, 17... Signal processing unit, 100, 100A, 100B... Transmitting device, 200, 200A, 200B... Transmitting/receiving device

Claims (9)

A radar system comprising a first transmitting device and a receiving device,
The first transmitting device includes:
a transmitting antenna;
signal synthesis for generating a first transmission signal that is transmitted by each of a plurality of transmission beams formed by the transmission antenna and directed in different directions, the first transmission signal using a different code sequence for each transmission beam; Department and
a transmitter that transmits a first transmission signal for each of the transmission beams from the transmission antenna,
The receiving device includes:
an array antenna having a plurality of antenna elements;
a signal separation unit that extracts the first transmission signal from the first reception signal received by each of the plurality of antenna elements using the different code sequence;
Using a first reception weight corresponding to a plurality of reception beams formed by the array antenna and having different pointing directions , receive beam signals of the plurality of reception beams having different pointing directions are generated for each transmission beam of a different code sequence. a receive beamformer that generates
For each of the reception beam signals including the first transmission signal, specify the pointing direction of the reception beam in which an object has been detected by CFAR processing, specify the pointing direction of the transmission beam from the code sequence, a signal processing unit that identifies the position of the object that reflected the first transmission signal based on the positions of the transmitting device and the receiving device, the pointing direction of the transmitting beam, and the pointing direction of the receiving beam; prepare,
radar system. A radar system comprising a first transmitting device and a receiving device,
The first transmitting device includes:
a transmitting antenna;
signal synthesis for generating a first transmission signal that is transmitted by each of a plurality of transmission beams formed by the transmission antenna and directed in different directions, the first transmission signal using a different code sequence for each transmission beam; Department and
a transmitter that transmits a first transmission signal for each of the transmission beams from the transmission antenna,
The receiving device includes:
an array antenna having a plurality of antenna elements;
Using a first reception weight corresponding to a plurality of reception beams formed by the array antenna and having different pointing directions, receive beam signals of the plurality of reception beams having different pointing directions are generated for each transmission beam of a different code sequence. a receive beamformer that generates
a signal separation unit that extracts the first transmission signal from each of the received beam signals using the different code sequences;
For each of the reception beam signals including the first transmission signal, specify the pointing direction of the reception beam in which an object has been detected by CFAR processing, specify the pointing direction of the transmission beam from the code sequence, a signal processing unit that identifies the position of the object that reflected the first transmission signal based on the positions of the transmitting device and the receiving device, the pointing direction of the transmitting beam, and the pointing direction of the receiving beam; prepare,
radar system. A radar system comprising a first transmitting device and a receiving device,
The first transmitting device includes:
a transmitting antenna;
a signal combining unit that generates a first transmission signal that is transmitted by each of a plurality of transmission beams formed by the transmission antenna and directed in different directions, the first transmission signal using a different frequency for each transmission beam; and,
a transmitter that transmits a first transmission signal for each of the transmission beams from the transmission antenna,
The receiving device includes:
an array antenna having a plurality of antenna elements;
a frequency division unit that divides the first received signal received by each of the plurality of antenna elements into divided signals for each of the different frequencies;
Using a first reception weight corresponding to a plurality of reception beams formed by the array antenna and having different directivity directions , receive beam signals of the plurality of reception beams having different directivity directions are determined for each transmission beam of a different frequency. a receiving beam forming unit that generates a beam;
For each of the reception beam signals including the first transmission signal, specify the pointing direction of the reception beam in which an object has been detected by CFAR processing, specify the pointing direction of the transmission beam from the frequency, and perform the first transmission. a signal processing unit that identifies the position of the object that reflected the first transmission signal based on the positions of the device and the receiving device, the pointing direction of the transmitting beam, and the pointing direction of the receiving beam. ,
radar system. A radar system comprising a first transmitting device and a receiving device,
The first transmitting device includes:
a transmitting antenna;
a signal combining unit that generates a first transmission signal that is transmitted by each of a plurality of transmission beams formed by the transmission antenna and directed in different directions, the first transmission signal using a different frequency for each transmission beam; and,
a transmitter that transmits a first transmission signal for each of the transmission beams from the transmission antenna,
The receiving device includes:
an array antenna having a plurality of antenna elements;
Using a first reception weight corresponding to a plurality of reception beams formed by the array antenna and having different directivity directions , receive beam signals of the plurality of reception beams having different directivity directions are determined for each transmission beam of a different frequency. a receiving beam forming unit that generates a beam;
a frequency dividing unit that divides each of the received beam signals into divided signals for each of the different frequencies;
For each of the receiving beam signals corresponding to the divided signals including the first transmitting signal, specifying the pointing direction of the receiving beam in which an object has been detected by CFAR processing, specifying the pointing direction of the transmitting beam from the frequency, signal processing for identifying the position of an object that reflected the first transmission signal based on the positions of the first transmitting device and the receiving device, the pointing direction of the transmitting beam, and the pointing direction of the receiving beam; comprising a section and a
radar system. comprising a second transmitting device that transmits a second transmission signal with a second transmission beam directed toward the position of the object specified by the signal processing unit,
The reception beam forming unit is configured to generate a second reception beam of a different code sequence using a second reception weight according to a plurality of second reception beams having different pointing directions and directed toward the position of the object specified by the signal processing unit. generating second reception beam signals for each of the plurality of second reception beams having different pointing directions for each of the two transmission beams;
The signal processing unit detects the object by the CFAR processing for each of the second receiving beam signals using a threshold smaller than the threshold used for the CFAR processing for the receiving beam signal, specifying the pointing direction of the second receiving beam that has detected the object; specifying the pointing direction of the second transmitting beam from the code sequence; and determining the positions of the second transmitting device and the receiving device; identifying the position of the object that reflected the second transmission signal based on the directional direction of the second transmission beam and the directional direction of the second reception beam;
The radar system according to claim 1 or claim 2 . comprising a second transmitting device that transmits a second transmission signal with a second transmission beam directed toward the position of the object specified by the signal processing unit,
The reception beam forming unit generates second reception beams of different frequencies using a second reception weight according to a plurality of second reception beams having different pointing directions and directed to the position of the object specified by the signal processing unit. generating a second receiving beam signal for each of the plurality of second receiving beams having different pointing directions for each transmitting beam;
The signal processing unit detects the object by the CFAR processing for each of the second receiving beam signals using a threshold smaller than the threshold used for the CFAR processing for the receiving beam signal, The pointing direction of the second receiving beam that detected the object is specified, the pointing direction of the second transmitting beam is specified from the frequency, and the positions of the second transmitting device and the receiving device are determined. identifying the position of the object that reflected the second transmission signal based on the directional direction of the second transmission beam and the directional direction of the second reception beam;
The radar system according to claim 3 or claim 4 . The second transmitting device determines an interval for transmitting the second transmission signal according to a distance to a position of the object specified by the signal processing unit.
The radar system according to claim 5 or claim 6 . The second transmitting device and the receiving device are formed as one device,
The radar system according to any one of claims 5 to 7 . The transmitter transmits a first transmit signal for each transmit beam from the transmit antenna in a time-division manner.
The radar system according to any one of claims 1 to 8 .

Images