radar equipment

Abstract

In MIMO radar systems using the FM-ICW system, interference occurs in the beat signal due to cross-correlation components when the target is at close range. [Solution] The radar transmitter 200 is a transmitting signal that repeats a transmitting chirp signal consisting of multiple pulses having a transmission interval and whose frequency changes over time, and applies one of several classified phase change amounts with respect to the distance to the target to each of the multiple pulses in the transmitting chirp signal, and outputs with a time shift amount; and the radar receiver 300 receives a receiving signal that repeats a receiving chirp signal consisting of multiple pulses of the transmitting chirp signal of the transmitting signal received from multiple receiving antennas 12 that receive the received wave that has been reflected off the target from the transmitted wave from multiple transmitting antennas 11, and generates a beat signal having a frequency that is the difference between the frequencies of the corresponding pulses of the transmitting chirp signal and the pulses of the receiving chirp signal, thereby obtaining distance information to the target.

Description

[Technical Field]

[0001] This disclosure relates to radar equipment. [Background technology]

[0002] As a radar system that detects the distance to a target, such as an object being observed, and its relative velocity to the target, the FMCW (Frequency Modulated Continuous Wave) radar system is well known. Furthermore, as a radar device for detecting targets beyond the line of sight, there is the HF radar (HF-SWR (Surface Wave Radar)) device, which uses radio waves in the HF (High Frequency) band, which are decameter waves with wavelengths of 10 to 100 m, known as surface waves.

[0003] HF radar systems have long wavelengths and require a large installation area when installing antennas, which imposes constraints. Therefore, the MIMO (Multiple Input Multiple Output) radar system, which improves angular resolution with the same installation area, is used, and Non-Patent Document 1 shows a MIMO surface wave radar system in the FMCW system. The surface wave radar system described in Non-Patent Document 1 is a radar system that uses a multiplexing method based on the TS-MIMO (Time Staggered MIMO) method, which is based on the FMCW method and uses a time-delayed chirp signal as the transmitted waveform. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] T. Fickenscher, el. al., “MIMO surface wave radar using time staggered FMCW chirp signals”, European Radar Conference, 2011. [Overview of the project] [Problems that the invention aims to solve]

[0005] In contrast to the installation of the radar system described in Non-Patent Document 1, there are further constraints on the installation area. If the transmitting antenna and receiving antenna are placed close together, the transmitted signal output from the transmitting antenna will be directly received by the receiving antenna, and the received signal reflected from the target will not be received. To avoid this problem, it is possible to adopt the FM-ICW (Frequency Modulated-Interrupted Continuous Wave) method, which allows for reception of the signal even when the transmitting and receiving antennas are placed in close proximity.

[0006] The inventors investigated various MIMO radar systems in the FM-ICW system and found that when there is no overlap between the pulses of the transmitted chirp signal and the pulses of the received chirp signal that correspond to the transmitted chirp signal pulses reflected from the target and received, the beat signals of the transmitted chirp signal pulses and the corresponding received chirp signal pulses have their peaks (cross-correlation components) at each pulse repetition frequency (PRF) on the beat spectrum suppressed due to pulsation, and are not interfered with by cross-correlation components.

[0007] However, depending on the distance between the radar device and the target, overlaps can occur between the pulses of the transmitted chirp signal and the corresponding pulses of the received chirp signal. This can result in pulse loss in the received chirp signal, and the beat signal may not have its PRF-specific peaks (cross-correlation components) suppressed by pulsation, leading to interference in the beat signal due to these cross-correlation components. It was found that interference resulted in problems such as a degradation of the signal-to-noise ratio (SNR) and an increase in the error of the angle measurement values ​​during MIMO beamforming.

[0008] This disclosure is made in view of the above-mentioned points, and aims to provide a MIMO radar system in the FM-ICW system that can suppress SNR degradation and reduce the increase in angle measurement errors even at distances to the target where there is overlap between the pulses of the transmitted chirp signal and the corresponding pulses of the received chirp signal, and pulse loss occurs in the pulses of the received chirp signal. [Means for solving the problem]

[0009] The radar device according to this disclosure includes a radar transmitting unit that outputs a transmission chirp signal consisting of multiple pulses having a pulse transmission interval and whose frequency changes over time, and which provides each of the multiple pulses in the transmission chirp signal with a phase change amount for one of the multiple classifications of distance to the target, and outputs with a time shift amount; and a radar receiving unit that receives a receiving signal consisting of multiple pulses corresponding to the multiple pulses of the transmission chirp signal of the transmission signal from multiple receiving antennas that receive a received wave from which the transmitted wave from the radar transmitting unit's transmission signal from multiple transmitting antennas has been reflected by the target, and generates a beat signal having a frequency that is the difference between the frequencies of the pulses of the transmission chirp signal of the corresponding transmission signal and the pulses of the receiving chirp signal of the receiving signal, and obtains distance information corresponding to the distance to the target. [Effects of the Invention]

[0010] According to this disclosure, in a MIMO radar system using the FM-ICW system, distance information can be obtained that suppresses the degradation of SNR and reduces the increase in angle measurement errors over a wide range of distances to the target. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the configuration of the radar device according to Embodiment 1. [Figure 2] This figure shows the time-frequency characteristics of the transmission signals #1 and #2 output from the radar transmission unit in the radar device according to Embodiment 1. [Figure 3] This figure shows the time amplitude characteristics of the transmitted signal #1 output from the radar transmitter in the radar device according to Embodiment 1. [Figure 4] This figure shows the relationship between the pulses of the transmitted chirp signal and the pulses of the received chirp signal in the time axis when the distance between the radar device and the target is greater than 0 and less than 2TPLS / C, in the radar device according to Embodiment 1. [Figure 5] This figure shows the relationship between the pulses of the transmitted chirp signal and the pulses of the received chirp signal in the time axis when the distance between the radar device and the target is a medium distance of 2 TPLS / C or more and less than 4 TPLS / C, according to the radar device of Embodiment 1. [Figure 6] This figure shows the relationship between the pulses of the transmitted chirp signal and the pulses of the received chirp signal in the time axis when the distance between the radar device and the target is a long distance of 4 TPLS / C or more and less than 6 TPLS / C, according to the radar device of Embodiment 1. [Figure 7] This figure shows the time amplitude characteristics and spectral characteristics of the radar device according to Embodiment 1 when the distance between the radar device and the target is medium distance. [Figure 8] This figure shows the beat frequency characteristics of the radar device according to Embodiment 1 when the distance between the radar device and the target is medium distance. [Figure 9] This figure shows the time amplitude characteristics and spectral characteristics of the radar device according to Embodiment 1 when the distance between the radar device and the target is short. [Figure 10] This figure shows the beat frequency characteristics when the radar device and the target are at a short distance, according to Embodiment 1 of the radar device. [Figure 11] This figure shows the beat frequency characteristics when a phase change corresponding to classification III of the distance between the radar device and the target is applied to the transmitted signal #2 in the radar device according to Embodiment 1, when the distance between the radar device and the target is short. [Figure 12]This figure shows an example of the hardware configuration of the signal processing unit in the radar device according to Embodiment 1. [Figure 13] This is a flowchart showing the operation of the radar device according to Embodiment 1. [Figure 14] This is a block diagram showing the configuration of the radar device according to Embodiment 2. [Figure 15] This is a flowchart showing the operation of the radar device according to Embodiment 2. [Figure 16] This is a block diagram showing the configuration of the radar device according to Embodiment 3. [Figure 17] This figure shows the relationship between the shift coefficient and the cross-correlation value in the radar device according to Embodiment 3. [Figure 18] This is a flowchart showing the operation of the radar device according to Embodiment 3. [Modes for carrying out the invention]

[0012] Embodiment 1. A radar device according to Embodiment 1 will be described using Figures 1 to 13. The radar system according to Embodiment 1 is a radar system that uses the TS-MIMO method in the FM-ICW system. The radar system according to Embodiment 1 is a radar system that uses radio waves in the HF band, which are decameter waves.

[0013] When the radar system according to Embodiment 1 is used as a high-frequency surface wave radar for long-range ocean surveillance, the target may be a high-speed boat or helicopter, etc. When the radar device according to Embodiment 1 is mounted on a vehicle such as an automobile and used as an automotive radar, the targets include other automobiles, pedestrians, or guardrails, etc.

[0014] As shown in Figure 1, the radar device according to Embodiment 1 comprises an antenna unit 100, a radar transmission unit 200, and a radar reception unit 300. The antenna section 100 has multiple transmitting antennas 111-11 Nand a plurality of receiving antennas 121 to 12 M It is composed of. N and M are natural numbers of 2 or more. N and M may be the same number or different numbers.

[0015] A plurality of transmitting antennas 111 to 11 N Among the N transmitting antennas, they are arranged in one dimension or two dimensions, and the intervals between adjacent transmitting antennas are equal. Each of the transmitting antennas 111 to 11 N converts the corresponding transmission signal input from the radar transmission unit 200 into a transmission wave and radiates (emits) the transmission wave into space.

[0016] A plurality of receiving antennas 121 to 12 M is arranged close to the group of transmitting antennas composed of a plurality of transmitting antennas 111 to 11 N Among the M receiving antennas, they are arranged in one dimension or two dimensions, and the intervals between adjacent receiving antennas are equal. Each of the receiving antennas 121 to 12 M is the transmitting antennas 111 to 11 N reflects the transmission wave radiated into space by the target, receives the reflected wave reflected by the target as a received wave, converts the received received wave into a received signal (reflected signal), and outputs it to the radar receiving unit 300.

[0017] The radar transmission unit 200 is a transmission signal that repeats a transmission chirp signal composed of a plurality of pulses whose frequencies change with the passage of time and have a pulse transmission interval. For each of the plurality of pulses of the transmission chirp signal in the transmission signal for the plurality of transmitting antennas 111 to 11 N gives a phase change amount φ h for any one of the classifications d classified into a plurality with respect to the distance to the target, and has a time shift amount T SFT and outputs it.

[0018] The radar transmission unit 200 has a MIMO modulation signal generation unit 21 and a modulation control unit 22. The radar transmission unit 200 may be used as a transmitter of the radar device. The MIMO modulation signal generation unit 21 has a time shift amount T set by the modulation control unit 22. SFT and the amount of phase change between pulses φ h Each transmitting antenna 111~11 N The system modulates each channel to generate transmission signals #1 to #N, and transmits each of the transmission signals #1 to #N to the corresponding transmitting antennas 111 to 111. N Output to [this location]. Transmitting antenna 111~11 N The channel corresponding to this will be referred to as the transmission channel below, and the transmission channel is transmitted via antennas 111-11 N There are N corresponding to this.

[0019] The MIMO modulation signal generation unit 21 has a sweep repetition period T WRI From a continuous reference signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, the pulse transmission interval T PRI Multiple (N) HIT It generates a pulsed reference signal composed of (1) pulses. HIT is a natural number greater than or equal to 2. The pulsed reference signal is the transmitted chirp reference signal.

[0020] The MIMO modulation signal generation unit 21 modulates the pulsed reference signal with respect to the time shift amount T set by the modulation control unit 22. SFT Based on this, transmitting antenna 111~11 N For the corresponding transmission channel, sequential time shift amount T SFT Shift it. The MIMO modulation signal generation unit 21 generates a sequential time shift amount T. SFT For each pulsed reference signal that shifts the pulse, the modulation control unit 22 sets the inter-pulse phase change amount φ for classification d. h Based on this, transmitting antenna 111~11 N Each of the multiple pulses of the corresponding pulsed reference signal has a phase change amount φ h Generates a transmitted chirp signal based on the given input. The MIMO modulation signal generation unit 21 is connected to the transmitting antennas 111-11 NThe transmitted chirp signal generated in response is swept with a repetition period T. WRI Each of the repeated transmission signals #1 to #N is transmitted using the corresponding transmitting antennas 111 to 11 N Output to [this location].

[0021] Each of the transmitted signals #1 to #N has its frequency changed over time by the modulation signal generation unit 21, and the pulse transmission interval T PRI A pulsed reference signal, which is composed of multiple pulses having the following characteristics, is subject to a time shift amount T set by the modulation control unit 22. SFT Based on this, multiple transmitting antennas 111-11 N Corresponding to the time shift amount T SFT The pulse phase change amount φ is shifted and set by the modulation control unit 22 for classification d. h Based on this, multiple transmitting antennas 111-11 N Each of the multiple pulses of the corresponding pulsed reference signal has a phase change amount φ h The given transmitted chirp signal is swept with a repetition period T. WRI This is a repeated signal.

[0022] Figures 2 and 3 show the time-frequency characteristics and time-amplitude characteristics of the transmitted signal output from the modulation signal generation unit 21. To avoid complexity in the explanation, we will explain the relationship for two transmission channels, and since this relationship extends to N transmission channels, Figure 2 shows the time-frequency characteristics of the two transmission channels of transmission signal #1 and transmission signal #2 output to transmission antenna 111 and transmission antenna 112, respectively, and Figure 3 shows the time-amplitude characteristics of transmission signal #1. Furthermore, the number of pulses in the transmitted chirp signal in the transmitted signal is N. HIT Five examples are given. Number of pulses N HIT The number is not limited to five; it is simply the number exemplified in Figures 2 and 3 to simplify the explanation.

[0023] The transmitted signal #1 has a sweep repetition period T. WRIIt has repeated transmitted chirp signals #11, #12, ... The transmitted chirp signal #11 has a sweep repetition period T, as shown in Figure 2. WRI The frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, and the signal is pulsed, consisting of multiple pulses, specifically five pulses #111 to #115 in Figure 2. In the transmitted chirp signal #11, as shown in Figure 3, each of the multiple pulses #111 to #115 has a pulse width T PLS It has a duty cycle of 1 / 3 and a pulse transmission interval T PRI It holds.

[0024] In the transmitted chirp signal #11, pulses #111 to #115 each represent the inter-pulse phase change φ for one of several classifications, classification d. h Based on the phase change amount φ h This will be decided. Pulses #111 to #115 are set by the modulation control unit 22 to one of the following three classifications, I to III, and the inter-pulse phase change amount φ is set by the modulation control unit 22. h This results in a pulse in which each pulse in the pulsed reference signal has been given a phase change.

[0025] Classification of distance to target I: The distance between the radar device and the target is greater than 0 C×T PLS In the case of a short distance of less than / 2, where the pulses of the received chirp signal overlap with the pulses of the corresponding transmitted chirp signal, and there are pulse gaps in the pulses of the received chirp signal. Note that C represents the speed of light. Classification of distance to target II: The distance between the radar device and the target is C × T PLS / 2 or more × 2 × C × T PLS For medium distances less than 2 / 2, where there is no overlap between the pulses of the transmitted chirp signal and the pulses of the received chirp signal, and there are no pulse drops in the pulses of the received chirp signal. Classification of distance to target III: The distance between the radar device and the target is 2 × C × T PLS / 2 or more 3×C×T PLSAt long distances of less than 2, when the pulse of the transmitted chirp signal does not overlap with the immediately preceding pulse in the corresponding received chirp signal, and there is a pulse gap in the received chirp signal.

[0026] For each of the classifications I through III, the phase change amount φ for each pulse of the transmitted chirp signal. h This is given by equation (1). φ h =exp{-j2π(d-1)D(h-1)} (1) In equation (1) above, h is the pulse number for the pulse of the transmitted chirp signal, and h ranges from 1 to H, with h being 1 to 5 in the examples shown in Figures 2 and 3. The pulse number H corresponds to the sweep repetition period T. WRI Number of pulses within N HIT It is the same as this. d is 1 for classification I, 2 for classification II, and 3 for classification III. D is the duty cycle, which in this example is 1 / 3.

[0027] One of the classifications from Classification I to Classification III, classification d, is set (selected), and the modulation control unit 22 calculates the phase change amount φ for one of the classifications from Classification I to Classification III, classification d, using the above equation (1). h This signal is supplied to the MIMO modulation signal generation unit 21. The phase of pulses #111 to #115 in the transmitted chirp signal #11 is the phase change amount φ based on the above equation (1) for the set classification d. h A phase change is given by this. The phase of pulses #211 to #215 in the transmitted chirp signal #21 is the phase change amount φ based on the above equation (1) for the set classification d. h A phase change is given by this.

[0028] Although not shown in the diagram, the phase of pulses #311 to #315 in transmit chirp signal #31 of transmit chirp signal #31 of transmit chirp signal #31 is the phase change amount φ based on the above equation (1) for the set classification d, similar to transmit chirp signals #11 and #21. hA phase change is given by..., and the phase of pulses #N11 to #N15 in the transmitted chirp signal #N1 of the transmitted signal #N is the phase change amount φ based on the above equation (1) for the set classification d. h A phase change is given by this.

[0029] The classification d assigned to transmission signals #1 through #N is determined by the modulation control unit 22 determining which of classifications I through III the distance information detected by the radar receiver 300 belongs to. After the modulation control unit 22 determines classification d, the modulation signal generation unit 21 sets a phase change amount φ for classification d for transmission signals #1 to #N. h The following is given: Phase change φ h This value is calculated based on equation (1) above, according to the pulse number.

[0030] The transmitted chirp signal #12 sweeps with respect to the transmitted chirp signal #11 with a repetition period T. WRI It will be output later. Transmit chirp signal #12, like transmit chirp signal #11, each has a pulse width T PLS It has a duty cycle of 1 / 3 and a pulse transmission interval T PRI It has a phase change amount φ for each of the classifications d set for it. h This is a pulsed signal composed of multiple pulses #121 to #125. The transmitted chirp signal is repeated the number of times set as the transmitted signal.

[0031] Transmitted signal #2 has a time shift amount T relative to transmitted signal #1. SFT Shifted and sweep repeat period T WRI It has repeated transmitted chirp signals #21, #22, ... As shown in Figure 2, the transmitted chirp signal #21 has a time shift amount T relative to the transmitted chirp signal #11. SFT Shifted, sweep repetition period T relative to transmitted signal #2 WRIThis is a pulsed signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, and which is composed of multiple pulses #211 to #215.

[0032] Similar to the transmit chirp signal #11, in the transmit chirp signal #21, pulses #211 to #215 each have a pulse width T PLS It has a duty cycle of 1 / 3 and a pulse transmission interval T PRI It holds. The transmitted chirp signal #21 is the phase change amount φ obtained by equation (1) above for classification d set to the same classification d as given to transmitted chirp signal #11. h This is applied to pulses #211 through #215, respectively.

[0033] As shown in Figure 2, the output start times of pulses #211 to #214 of the transmitted chirp signal #21 are set to be the same as the output start times of pulses #112 to #115 of the transmitted chirp signal #11, by a time shift amount T. SFT This is set by the modulation control unit 22. Therefore, the frequency difference f between the transmitted chirp signal #21 and the transmitted chirp signal #11 SFT The relationship is as shown in Figure 2.

[0034] Time shift amount T SFT The setting is the pulse width T on the beat spectrum. PLS The reciprocal of 1 / T PLS The frequency difference f between transmitted signal #1 and transmitted signal #2 SFT It will be made to be so. frequency difference f SFT This can be expressed by the following equation (2). f SFT =T SFT ×(B / T WRI ) (2) Sweep repetition period T WRI This can be expressed by the following equation (3). T WRI =N HIT ×T PRI (3)

[0035] Time shift amount TSFT can be expressed by the following formula (4)< / font> by substituting formula (3) into formula (2) above.< / font> T SFT =f SFT ×T WRI / B=f SFT ×T PRI ×N HIT / B (4) When f SFT =1 / T PLS is substituted into the above formula (4), it can be expressed by the following formula (5). T SFT =T PRI ×N HIT / (B×T PLS ) (5)

[0036] [N HIT / (B×T PLS )] is set as the shift coefficient N SFT of the parameter so that it becomes an integer. The above formula (5) can be expressed by the following formula (6). T SFT =T PRI ×N SFT [[ID=5 1]](6) As understood from the above formula (6), the time shift amount T SFT can be set as a value obtained by multiplying the shift coefficient N PRI made an integer by the pulse transmission interval T SFT .

[0037] The transmission chirp signal #22 is output after the sweep repetition period T WRI from the transmission chirp signal #21. The transmission chirp signal #​​​​​​​​

[0038] Although not shown in the diagram, the transmission chirp signals #31 to #N1 are sequentially shifted by a time amount T from transmission chirp signal #21. SFT Shifted and sweep repeat period T WRI Output starts within the system. The transmitted chirp signals in each of the transmitted signals #3 through #N are the same as the transmitted chirp signal in transmitted signal #1, with a pulse transmission interval T PRI It consists of multiple pulses having the same phase change amount φ as one of the classifications d set by the modulation control unit 22 from classification I to classification III, that is, the same classification d set as the classification d given in the transmitted chirp signal #11. h These are the signals given to each pulse.

[0039] The radar receiver 300 has multiple transmitting antennas 111-11 N Multiple receiving antennas 121-12 receive the received waves, which are the transmitted waves from the radar transmitter 200, transmitted signals #1-#N, reflected off the target. M The system receives a received signal that repeats a received chirp signal composed of multiple pulses corresponding to the transmitted chirp signals #1 to #N. It generates a beat signal with a frequency that is the difference between the frequencies of the pulses of the transmitted chirp signals #1 to #N and the pulses of the received chirp signal of the received signal, thereby obtaining distance information. Multiple transmitting antennas 111-11 N and multiple receiving antennas 121-12 M Therefore, each receiving antenna 121~12 M Since it has N receiving channels, the output from the radar receiver 300 has (N × M) receiving channels.

[0040] The radar receiving unit 300 includes a signal receiving unit 31, a demodulation unit 32, a range calculation unit 33, a Doppler calculation unit 34, a MIMO beamforming unit 35, and a detection unit 36. The signal receiving unit 31 has multiple receiving antennas 121-12 MThe received signals #1 to #M from each device are converted from analog to digital (AD), their frequencies are converted, they are converted into beat signals, and these beat signals are output.

[0041] Each of the received signals #1 to #M has a received signal corresponding to the transmitted signals #1 to #N. In other words, each of the received signals #1 to #M has received signals #11 to #M1, which are the received waves from the transmitted wave of transmission signal #1 that are reflected by the target; received signals #12 to #M2, ..., which are the received waves from the transmitted wave of transmission signal #2 that are reflected by the target; and received signals #1N to #MN, which are the received waves from the transmitted wave of transmission signal #N that are reflected by the target.

[0042] In short, each of the received signals #1 to #M has N received signals corresponding to each of the transmitted signals #1 to #N, and the signal receiving unit 31 forms (M × N) receiving channels as its output. For example, received signal #1 has N received signals corresponding to each of the transmitted signals #1 to #N, and received signal #1 has N received signals corresponding to each of the transmitted signals #1 to #N.

[0043] Since the signal processing for each of the received signals #1 to #M is essentially the same, we will primarily explain received signal #1 to avoid unnecessary complexity. When the signal receiving unit 31 converts the received signal #1 into a beat signal, the time shift amount T is assigned to the transmitted signals #1 to #N relative to the received signals #11 to #1N in the received signal #1. SFT At the appropriate timing, a reference signal is generated, which is a mix of the corresponding transmitted signals #1 to #N and received signals #11 to #1N, and converted into a beat signal.

[0044] Each of the received signals #11 to #1N, like the transmitted signals #1 to #N, is a received signal that repeats a received chirp signal consisting of multiple pulses whose frequency changes over time and which have the same pulse reception interval as the pulse transmission interval. Each of the multiple pulses of the received chirp signal in received signal #11 corresponds to a phase shift amount φ relative to the set classification d given to each of the multiple pulses of the transmitted chirp signal in the corresponding transmitted signal #1. h It exhibits the same phase change. Similarly, each of the multiple pulses of the received chirp signal in each of the received signals #12 to #1N corresponds to the phase change amount φ of the multiple pulses of the transmitted chirp signal in each of the corresponding transmitted signals #2 to #N, with respect to the set classification d. h It exhibits the same phase change.

[0045] Mixing the corresponding transmit signals #1 to #N and receive signals #11 to #1N means mixing the pulses of the transmit chirp signals #1 to #N and the pulses of the receive chirp signals #11 to #1N, which are in a corresponding relationship. The beat signal has a frequency that is the difference between the pulse frequencies of the transmitted chirp signal of the corresponding transmitted signal and the pulse frequencies of the received chirp signal of the received signal.

[0046] Since the signal processing for each of the received signals #11 to #1N in the received signal #1 is essentially the same, we will focus on explaining received signal #11 to avoid unnecessary complexity. The signal receiving unit 31 generates a beat signal for each corresponding transmitted chirp signal #11, #12, ... of transmitted signal #11 and each received chirp signal #111, #112, ... of received signal #11, and for each pulse #111 to #115, #1121 to #1125, ... of the corresponding transmitted chirp signals #11, #12, ... of transmitted signal #11 and #12, ... of transmitted signal #11 and #12, ... of received signal #11 and #112, ... of received signal #11.

[0047] When the distance between the radar device and the target is medium and there are no pulse drops in the received chirp signal pulses, the spectrum of the received chirp signal pulses will have a bandwidth of 1 / T, the reciprocal of the pulse width, as shown in Figure 7. PLS Therefore, classification d for the distance between the radar device and the target is classification II.

[0048] The bandwidth is the reciprocal of the pulse width, 1 / T. PLS Therefore, the frequency difference f between transmitted signal #1 and transmitted signal #2 at the same time is SFT pulse width T PLS The reciprocal of 1 / T PLS As this setting is configured, as shown in Figure 8, the beat signal of the pulse of the transmitted chirp signal and the corresponding pulse of the received chirp signal, the beat signal shown as "Transmit 1, Demodulate 1" in Figure 8, has its peaks (cross-correlation components) for each PRF on the beat spectrum suppressed due to pulsation, and is not interfered with by the cross-correlation components.

[0049] In Figure 8, the horizontal axis represents beat frequency, and the vertical axis represents power. "Transmit 1, Demodulate 1" is, for example, a beat signal that indicates the frequency difference between the pulse #111 of the transmit chirp signal #11 of the corresponding transmit signal #1 and the pulse #1111 of the receive chirp signal #111 of the received signal #11. This beat frequency is dependent on the distance to the target. "Transmit 2, Demodulate 1" indicates a beat signal that shows the frequency difference between pulse #111 of the transmit chirp signal #11 of transmit signal #1 and pulse #2111 of the receive chirp signal #21 of receive signal #21, which corresponds to transmit signal #2.

[0050] Furthermore, Figure 8 shows the peaks (cross-correlation components) for each PRF on the beat spectrum due to the pulse of the received chirp signal #21 corresponding to the transmitted signal #2, with respect to pulse #111 of the transmitted chirp signal #11 of the transmitted chirp signal #1 of the transmitted signal #1. Pulsation of the transmitted chirp signal generates an envelope, and the cross-correlation value, which indicates the strength of the cross-correlation component, depends on the size of the envelope. The envelope shown in Figure 8 only shows the main lobe. As can be seen from Figure 8, the beat signal in "Transmit 1, Demodulate 1" is not interfered with because the peaks (cross-correlation components) for each PRF caused by pulsation are suppressed by the envelope.

[0051] In other words, in Figure 8, the beat frequency of the beat signal indicated by "Transmit 1, Demodulate 1" depends on the distance to the target, and by obtaining this beat frequency, the distance to the target can be determined. Furthermore, as is clear from Figure 8, for the beat signal shown as "Transmit 1, Demodulate 1," there are no cross-correlation components that match the beat frequency of the beat signal, and the beat signal is not interfered with by cross-correlation components. Therefore, when the distance between the radar device and the target is medium, the phase change amount φ shown by equation (1) above in Class II h Based on this, a phase change amount should be applied to the pulse of the transmitted chirp signal in the transmitted signal.

[0052] If the radar device is at a short distance from the target and there are pulse gaps in the received chirp signal, the pulse width of the missing pulse is called pulse width T. PLS The value obtained by multiplying by the missing coefficient α is αT. PLS Therefore, the spectrum of a pulse with a missing received chirp signal has a bandwidth of pulse width αT, as shown in Figure 9. PLS The reciprocal of 1 / αT PLS Therefore, the missing coefficient α is greater than 0 and less than 1. Bandwidth 1 / αT PLS The bandwidth is 1 / T when there are no pulse drops in the pulse. PLS This indicates broadbanding. Classification d for the distance between the radar device and the target is classification I.

[0053] Bandwidth 1 / αT PLS By broadening the bandwidth, the phase change amount φ shown by equation (1) above in classification II described above becomes h Based on this, when a phase change is applied to the pulse of the transmitted chirp signal of the transmitted signal, as shown in Figure 10, the envelope due to pulsation in the transmitted chirp signal of the transmitted signal expands in the beat frequency direction. As a result, the beat signals of the pulse of the transmitted chirp signal and the corresponding pulse of the received chirp signal do not have their peaks (cross-correlation components) for each PRF on the beat spectrum due to pulsation suppressed, and interference occurs.

[0054] In Figure 10, the horizontal axis represents beat frequency, and the vertical axis represents power. "Transmit 1, Demodulate 1" is, for example, a beat signal that indicates the frequency difference between the pulse #111 of the transmit chirp signal #11 of the corresponding transmit signal #1 and the pulse #1111 of the receive chirp signal #111 of the receive signal #11. "Transmit 2, Demodulate 1" indicates a beat signal showing the frequency difference between pulse #111 of the transmit chirp signal #11 of transmit signal #1 and pulse #2111 of the receive chirp signal #211 of receive signal #21, which corresponds to transmit signal #2.

[0055] Furthermore, Figure 10 shows the peaks (cross-correlation components) for each PRF on the beat spectrum due to the pulse of the received chirp signal #21 corresponding to the transmitted signal #2, with respect to pulse #111 of the transmitted chirp signal #11 of the transmitted chirp signal #11 of the transmitted signal #1. The envelope shown in Figure 10 only shows the main lobe.

[0056] As can be seen from Figure 10, for the beat signal in "Transmit 1, Demodulate 1", the spread of the envelope in the beat frequency direction due to pulsing of the transmitted chirp signal in the transmitted signal causes a cross-correlation component that matches the beat frequency of the beat signal to appear, and the beat signal is interfered with by this cross-correlation component.

[0057] Therefore, in Embodiment 1, the phase change amount φ for classification III obtained by equation (1) above is applied to each of the multiple pulses of the transmitted chirp signal in each of the transmitted signals #1 to #N. h Give. Each of the multiple pulses of the received chirp signal in each of the received signals #11 to #1N corresponds to the phase change amount φ applied to each of the multiple pulses of the transmitted chirp signal in each of the corresponding transmitted signals #1 to #N. h It exhibits the same phase change.

[0058] For each of the multiple pulses of the transmitted chirp signal in each of the transmitted signals #1 to #N, the phase change amount φ for classification III obtained by equation (1) above is applied.h When given, for example as shown in Figure 11, the beat frequency of the cross-correlation component shifts in the beat frequency direction on the beat spectrum relative to the beat frequency of the cross-correlation component shown in Figure 10, and the frequency [(d-1)×D×f PRF Shift.

[0059] Figure 11 shows the phase change amount φ compared to Figure 10. h The phase change φ from classification II to classification III h The beat frequency characteristics when this is changed are shown. In Figure 11, "Transmit 1, Demodulate 1" is a beat signal that, as an example, shows the frequency difference between the pulse #111 of the transmit chirp signal #11 of the corresponding transmit signal #1 and the pulse #1111 of the receive chirp signal #111 of the receive signal #11. "Transmit 2, Demodulate 1" indicates a beat signal showing the frequency difference between pulse #111 of the transmit chirp signal #11 of transmit signal #1 and pulse #2111 of the receive chirp signal #211 of receive signal #21, which corresponds to transmit signal #2.

[0060] As shown in Figure 11, in Figure 10, the cross-correlation component whose beat frequency matches the beat signal in "Transmit 1, Demodulate 1" is the shift frequency [(d-1) × D × f PRF The signal is shifted, eliminating the cross-correlation component that matches the beat frequency of the beat signal in "Transmit 1, Demodulate 1," and the beat signal in "Transmit 1, Demodulate 1" is no longer interfered with by the cross-correlation component.

[0061] In other words, the phase change amount φ for classification III obtained by equation (1) above is applied to the pulses of the transmitted chirp signals #1 and #2. h Since this is given, the beat signal of the pulse of the transmitted chirp signal and the corresponding pulse of the received chirp signal are not interfered with by the cross-correlation component for each PRF on the beat spectrum due to the pulsation of the transmitted chirp signal, and the influence of the cross-correlation component on the calculation of the distance to the target is reduced.

[0062] The demodulation unit 32, for each (N × M) receiving channel of the output from the signal receiving unit 31, receives the phase change amount φ in the set classification d that the modulation control unit 22 has given to the modulation signal generation unit 21 for each transmitted signal #1 to #N. h The beat signal from the signal receiving unit 31 is corrected and demodulated using this method.

[0063] In other words, the demodulation unit 32 measures the pulse of the chirp signal of the corresponding transmitted signal #1 and the beat signal of each pulse in the chirp signals of the received signals #11 to #M1, and the phase change amount φ in the set classification d applied to the transmitted signal #1. h The phase change amount φ in the set classification d applied to the transmitted signal #2 is given to the corresponding pulse of the chirp signal of transmitted signal #2 and the beat signal of each pulse in the chirp signals of received signals #12 to #M2. h The phase change amount φ in the set classification d given to the transmitted signal #N is given to the pulse of the chirp signal of the transmitted signal #N and the beat signal of each pulse in the chirp signals of the received signals #1N to #MN, respectively. h The phase change amount φ in the set classification d corresponding to the beat signal in (N×M) receiving channels is given. h Correct using this method.

[0064] In short, the demodulation unit 32 controls the transmitting antennas 111-11 N Number and receiving antenna 121~12 M The number of beat signals obtained for each of the multiple (N×M) receiving channels corresponds to the phase change amount φ in the set classification d for each receiving channel. h The beat signal is corrected and demodulated using this method.

[0065] The range calculation unit 33 calculates range data (beat spectrum) by performing a range Fourier transform (FFT) on the demodulated beat signal obtained by the demodulation unit 32. The Doppler calculation unit 34 sweeps the range data obtained by the range calculation unit 33 with a sweep repetition period T. WRIThe sweep is repeated, and a Fourier transform (Doppler FFT) is performed between them to convert the range data into a Doppler spectrum and obtain a Doppler profile.

[0066] The MIMO beamforming unit 35 uses the Doppler profile obtained by the Doppler calculation unit 34 to generate multiple receiving antennas 121-12 M MIMO beam data is obtained by integrating the Doppler spectra corresponding to each received signal #1 to #M, or by integrating the Doppler spectra corresponding to each (N × M) received channel. The detection unit 36 ​​performs target detection processing such as CFAR (Constant False Aram Rate) processing to obtain distance information corresponding to the distance to the target and speed information corresponding to the relative speed to the target.

[0067] The range calculation unit 33, the Doppler calculation unit 34, the MIMO beam formation unit 35, and the detection unit 36 ​​constitute the distance information acquisition unit. The distance information acquisition unit performs a Fourier transform on the demodulated beat signal obtained by the demodulation unit 32 and executes target detection processing to obtain distance information corresponding to the distance to the target.

[0068] Furthermore, the range calculation unit 33, the Doppler calculation unit 34, the MIMO beam forming unit 35, and the detection unit 36 ​​constitute the velocity information acquisition unit. The speed information acquisition unit performs a Fourier transform on the demodulated beat signal obtained by the demodulation unit 32 and executes target detection processing to obtain speed information corresponding to the relative speed with respect to the target.

[0069] The MIMO modulation signal generation unit 21 and the signal receiving unit 31 constitute the signal generation / receiving unit 400. The modulation control unit 22, demodulation unit 32, range calculation unit 33, Doppler calculation unit 34, MIMO beamforming unit 35, and detection unit 36 ​​constitute the signal processing unit 500. The signal processing unit 500 is implemented by a computer hardware configuration and includes a processor 51 such as a CPU (Central Processing Unit) and memory 52, as shown in Figure 12. Memory 52 consists of ROM (Read Only Memory) and RAM (Random Access Memory).

[0070] The processing details of the signal processing unit 500, that is, the time shift amount T by the modulation control unit 22. SFT and the amount of phase change between pulses φ h The settings, as well as the processing details by the demodulation unit 32, range calculation unit 33, Doppler calculation unit 34, MIMO beamforming unit 35, and detection unit 36, are stored as a program in the ROM of the memory 52.

[0071] The program stored in ROM is first loaded into RAM in memory 52 by the processor 51, and the processor 51 then executes various processes based on the program loaded into RAM. Alternatively, an FPGA (Field Programmable Gate Array) may be used as the processor 51, a program indicating the processing details of the signal processing unit 500 may be implemented on the FPGA, and various processes may be executed by the FPGA.

[0072] Next, the operation of the radar device according to Embodiment 1 will be explained using the flowchart shown in Figure 13. In step ST1, the modulation control unit 22 controls the inter-pulse phase change amount φ h and time shift amount T SFT This will be set.

[0073] Inter-pulse phase change φ h For any one of the classifications d set from classification I to classification III, the phase change amount φ calculated by (1) above is used. h That is the case. Classification d is set by the modulation control unit 22 by determining the distance information detected by the radar receiver unit 300.

[0074] In step ST2, the modulation signal generation unit 21 changes the frequency over time, and the pulse transmission interval T PRIA pulsed reference signal composed of multiple pulses having the following time shift amount T from the modulation control unit 22: SFT Using this, the time shift amount T SFT This generates a shifted, pulsed reference signal.

[0075] The modulation signal generation unit 21 generates a phase change amount φ calculated by (1) above for one of the classifications d set by the modulation control unit 22 from classification I to classification III. h This results in a phase change amount φ for each of the multiple pulses of the generated pulsed reference signal. h This generates the given transmission signals #1 to #N.

[0076] The modulation signal generation unit 21 generates transmission signals #1 to #N and transmits them to the corresponding transmission antennas 111 to 11 N Output to [this location]. Step ST2 involves the generation of modulated transmission signals #1 to #N by the modulation signal generation unit 21, and the transmission antennas 111 to 111. N This step involves executing the output of the modulated transmission signals #1 to #N.

[0077] In step ST3, the transmission signals #1 to #N from the modulation signal generation unit 21 are input to the transmitting antennas 111 to 11. N Each emits (transmits) a transmitted wave into space based on transmission signals #1 to #N. In step ST4, multiple receiving antennas 121-12 M The transmitting antenna is 111~11 N The transmitted wave radiated into space is reflected by the target, the reflected wave is received as a received wave, and the received wave is converted into a received signal (reflected signal) #1 to #M.

[0078] In step ST5, receiving antennas 121-12 M The signal receiving unit 31, upon receiving signals #1 to #M from the input, performs AD conversion on each of the input received signals #1 to #M, performs frequency conversion, and outputs a beat signal. The received signals #11 to #M1, #1N to #MN, corresponding to the transmitted signals #1 to #N in each of the received signals #1 to #M, are the phase change amount φ with respect to one of the classifications d set from classification I to classification III given to the transmitted signals #1 to #N. h It holds.

[0079] When the signal receiving unit 31 converts the received signals #11 to #1N, ~, and #M1 to #MN into beat signals, the time shift amount (n × T) given to the transmitted signals #1 to #N is used. SFT At timings corresponding to (n is 1 to N-1), the signal receiving unit 31 performs mixing of the received signals #11 to #M1, ~, #1N to #MN with the transmitted signals #1 to #N.

[0080] For each of the received signals #11 to #M1, ~, and #1N to #MN corresponding to the transmitted signals #1 to #N, the phase change amount φ is set for one of the classifications d from classification I to classification III. h Because of this, whether the distance to the target is short or long, the beat signals of the transmitted chirp signal pulse and the corresponding received chirp signal pulse have their cross-correlation components for each PRF suppressed on the beat spectrum due to pulsation, making them less susceptible to interference from cross-correlation components.

[0081] In step ST6, the demodulation unit 32, upon receiving the beat signal from the signal receiving unit 31, applies a phase change amount φ to each transmitted signal #1 to #N for each (N × M) receiving channel relative to the output from the signal receiving unit 31. h The phase of the beat signal input from the signal receiving unit 31 is corrected using this method, and the demodulated beat signal is obtained by demodulating it.

[0082] In step ST7, the range calculation unit 33 performs a Fourier transform on the demodulated beat signal to calculate range data (beat spectrum). In step ST8, the Doppler calculation unit 34 sweeps the range data with a repeating period T. WRI A Doppler profile is obtained by performing a Fourier transform between repeated sweeps.

[0083] In step ST9, the MIMO beamforming unit 35 uses a Doppler profile to form multiple receiving antennas 121-12 M MIMO beam data is obtained by integrating the Doppler spectra corresponding to each received signal #1 to #M, or by integrating the Doppler spectra corresponding to each (M × N) received channel.

[0084] In step ST10, the detection unit 36 ​​performs target detection processing and obtains distance information corresponding to the distance to the target and speed information corresponding to the relative speed to the target. A program that instructs the computer to execute the processing steps from step ST5 to step ST10 is stored in memory 52.

[0085] The radar system according to Embodiment 1 is a radar system using the TS-MIMO method in the FM-ICW system, wherein the radar transmitter 200 is a transmitting signal that repeats a transmission chirp signal consisting of multiple pulses with a pulse transmission interval, the frequency of which changes over time, and the transmitted signal is given a phase change amount for one of the multiple classifications d of the distance to the target to each of the multiple pulses in the transmission chirp signal, and the transmitted signal is output with a time shift amount set for multiple transmitting antennas, so that when the radar receiver 300 generates a beat signal, there is overlap between the pulses of the transmission chirp signal of the corresponding transmitting signal and the pulses of the receiving chirp signal of the receiving signal, and even if there are pulse loss in the pulses of the receiving chirp signal, the beat signal is less susceptible to interference from the cross-correlation components for each PRF on the beat spectrum due to pulsation. As a result, distance information is obtained that suppresses the degradation of SNR and reduces the increase in angle measurement errors over a wide range of distances to the target.

[0086] Embodiment 2. A radar device according to Embodiment 2 will be described with reference to Figures 14 and 15. The radar device according to Embodiment 1 sets a phase change amount φ for each of the multiple pulses of the transmitted chirp signal in the transmitted signal to multiple transmitting antennas, with respect to one of the classifications d set from classification I to classification III. h This configuration uses the given signal as the transmission signal.

[0087] In contrast, the radar device according to Embodiment 2 differs in that it applies a frequency shift amount to one of the classifications d set from classification I to classification III to multiple pulses of the transmitted chirp signal in the transmitted signal to multiple transmitting antennas, but is otherwise the same.

[0088] Therefore, the following description will focus on the differences from the radar device according to Embodiment 1. In Figures 14 and 15, the same reference numerals as those used in Figures 1 to 13 indicate the same or corresponding parts.

[0089] As shown in Figure 14, the radar device according to Embodiment 2 comprises an antenna unit 100, a radar transmission unit 200a, and a radar reception unit 300a. The radar transmitter 200a is a transmission signal that repeats a transmission chirp signal consisting of multiple pulses with a pulse transmission interval, the frequency of which changes over time, and multiple transmission antennas 111-11 N The transmitted signal is given a frequency shift amount δf(t) for one of several classifications d based on the distance to the target, and a time shift amount T SFT It outputs with the following characteristics.

[0090] The radar transmission unit 200a includes a MIMO modulation signal generation unit 21a and a modulation control unit 22a. The MIMO modulated signal generation unit 21a generates a time shift amount T set by the modulation control unit 22a. SFT And the frequency shift amount δf(t) for each transmitting antenna 111~11 N The system modulates each channel to generate transmission signals #1 to #N, and transmits each of the transmission signals #1 to #N to the corresponding transmitting antennas 111 to 111. N Output to [this location].

[0091] The MIMO modulation signal generation unit 21a has a sweep repetition period T WRI From a continuous reference signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, the pulse transmission interval T PRI Multiple (N) HIT It generates a pulsed reference signal composed of individual pulses. This pulsed reference signal is the transmitted chirp reference signal.

[0092] The MIMO modulation signal generation unit 21a modulates the pulsed reference signal with respect to the time shift amount T set by the modulation control unit 22a. SFT Based on this, transmitting antenna 111~11 N Sequential time shift amount T for the corresponding transmission channel SFT Shift it. The MIMO modulation signal generation unit 21a generates a sequential time shift amount T SFT For each pulsed reference signal that shifts the frequency, the modulation control unit 22a sets the frequency shift amount δf(t) for classification d, and transmits the antennas 111-11 N A transmit chirp signal is generated by applying a frequency shift amount δf(t) to multiple pulses of the corresponding pulsed reference signal.

[0093] The frequency shift amount δf(t) applied to multiple pulses is the same value in the set classification d. The MIMO modulation signal generation unit 21a is connected to the transmitting antennas 111-11 N The transmitted chirp signal generated in response is swept with a repetition period T. WRI Each of the repeated transmission signals #1 to #N is transmitted using the corresponding transmitting antennas 111 to 11 N Output to [this location].

[0094] Each of the transmitted signals #1 to #N has its frequency changed over time by the modulation signal generation unit 21a, and the pulse transmission interval T PRI A pulsed reference signal, which is composed of multiple pulses having the following characteristics, is subjected to a time shift amount T set by the modulation control unit 22a.SFT Based on this, multiple transmitting antennas 111-11 N Corresponding to the time shift amount T SFT The frequency is shifted, and based on the frequency shift amount δf(t) for classification d set by the modulation control unit 22a, multiple transmitting antennas 111~11 N A transmitted chirp signal, in which multiple pulses of a corresponding pulsed reference signal are given a frequency shift amount δf(t), is swept with a repetition period T. WRI This is a repeated signal.

[0095] The transmitted signal #1 has a sweep repetition period T. WRI It has repeated transmitted chirp signals #11, #12, ... Transmitted signals #2 to #N are the same as transmitted signal #1. In the transmitted chirp signal #11, pulses #111 to #115 have their frequency shift amount determined based on the frequency shift amount.

[0096] Pulses #111 to #115 are pulses to which a frequency shift amount δf(t) is applied to the pulses in the pulsed reference signal, based on a frequency shift amount δf(t) for classification d, which is set by the modulation control unit 22a to one of the three classifications I to III described above.

[0097] The frequency shift amount δf(t) from classification I to classification III is given by equation (7). δf(t)=exp{-j2π(d-1)Df PRF t}(7) One of the classifications from Classification I to Classification III, classification d, is set (selected), and the modulation control unit 22 provides the MIMO modulation signal generation unit 21 with the frequency shift amount δf(t) calculated by equation (7) above for one of the classifications from Classification I to Classification III, classification d.

[0098] The frequency shift amount of pulses #111 to #115 in the transmitted chirp signal #11 is given by the frequency shift amount δf(t) based on equation (7) above, for the set classification d. The frequency shift amount of pulses #211 to #215 in the transmitted chirp signal #21 is given by the frequency shift amount δf(t) based on equation (7) above for the set classification d.

[0099] For transmission signals #3 to #N, similar to transmission chirp signals #11 and #21, the frequency shift amount of pulses #311 to #315 in transmission chirp signal #31 of transmission signal #3 is given by the frequency shift amount δf(t) based on equation (7) above for the set classification d, ... and the frequency shift amount of pulses #N11 to #N15 in transmission chirp signal #N1 of transmission signal #N is given by the frequency shift amount δf(t) based on equation (7) above for the set classification d.

[0100] The classification d assigned to transmission signals #1 through #N is determined by the modulation control unit 22 determining which of classifications I through III the distance information detected by the radar receiver 300 belongs to. After the modulation control unit 22 determines classification d, the modulation signal generation unit 21 provides a frequency shift amount δf(t) for the set classification d from the transmission signal #1 to the transmission signal #N. The frequency shift amount δf(t) is a value calculated based on the above equation (7).

[0101] Each of the transmission signals #1 to #N is given a frequency shift amount δf(t) relative to classification d set by the modulation control unit 22a by the modulation signal generation unit 21a, and a time shift amount T set by the modulation control unit 22a using the above equation (5) SFT Based on this, the modulation signal generation unit 21a generates the corresponding transmitting antennas 111-11 N It will be output to [this location].

[0102] The radar receiver 300a has multiple transmitting antennas 111-11 N Multiple receiving antennas 121-12 receive the received waves, which are the transmitted waves from the radar transmitter 200, transmitted signals #1-#N, reflected off the target. MThe system receives a received signal that repeats a received chirp signal composed of multiple pulses corresponding to the transmitted chirp signals #1 to #N. It generates a beat signal with a frequency that is the difference between the frequencies of the pulses of the transmitted chirp signals #1 to #N and the pulses of the received chirp signal of the received signal, thereby obtaining distance information.

[0103] The radar receiving unit 300a includes a signal receiving unit 31, a demodulation unit 32a, a range calculation unit 33, a Doppler calculation unit 34, a MIMO beamforming unit 35, and a detection unit 36. Multiple receiving antennas 121-12 are input to the signal receiving unit 31. M Each of the received signals #1 to #M consists of the received signals #11 to #M1, ~, and #1N to #MN, which correspond to the transmitted signals #1 to #N. Each of the received signals #11 to #M1, ~, and #1N to #MN, corresponding to each of the transmitted signals #1 to #N, has the same frequency shift amount δf(t) as the classification d given to the corresponding transmitted signals #1 to #N.

[0104] Each of the received signals #11 to #M1, ~, and #1N to #MN is shifted by a frequency shift amount δf(t) relative to classification d set by the modulation control unit 22a. When the distance between the radar device and the target is short and there are pulse drops in the received chirp signal pulses, if a frequency shift amount δf(t) for classification III obtained by equation (7) above is given to the pulses of the transmitted chirp signal, the beat frequency of the cross-correlation component shifts in the beat frequency direction on the beat spectrum compared to when a frequency shift amount δf(t) for classification II is given. [(d-1)×D×f PRF Shift.

[0105] As a result, the beat signal of the pulse of the transmitted chirp signal and the corresponding pulse of the received chirp signal has a shift frequency [(d-1) × D × f PRFBecause it is shifted, the cross-correlation component that matches the beat frequency of the beat signal, which was previously matched at close range, disappears, and the beat signal is no longer interfered with by the cross-correlation component. In other words, the beat signal is pulsed, suppressing the cross-correlation components for each PRF on the beat spectrum. This prevents interference from these cross-correlation components, reducing their influence on the calculation of the distance to the target.

[0106] The demodulation unit 32a corrects and demodulates the beat signal from the signal receiving unit 31 for each (N × M) receiving channel of the output from the signal receiving unit 31 using the frequency shift amount δf(t) for each transmission signal #1 to #N that is set by the modulation control unit 22a to the modulation signal generation unit 21a.

[0107] In other words, the demodulation unit 32 applies a frequency shift amount δf(t) for each of the received signals #1 to #M to the pulse of the chirp signal of the corresponding transmitted signal #1 and the beat signal for each pulse in the chirp signals of each of the received signals #11 to #M1 with respect to the set classification d given to the transmitted signal #1; applies a frequency shift amount δf(t) for each of the pulses of the chirp signal of the corresponding transmitted signal #2 and the beat signal for each pulse in the chirp signals of each of the received signals #12 to #M2 with respect to the set classification d given to the transmitted signal #2; ... applies a frequency shift amount δf(t) for each of the chirp signals of the corresponding transmitted signal #N and the beat signal for each pulse in the chirp signals of each of the received signals #1N to #MN with respect to the set classification d given to the transmitted signal #N; and corrects the beat signals in (N × M) received channels using the frequency shift amount δf(t) for each of the transmitted signals with respect to the set classification d given to the transmitted signals.

[0108] In short, the demodulation unit 32a controls the transmitting antennas 111-11 N Number and receiving antenna 121~12 M The beat signal for each of the multiple (N×M) receiving channels obtained by the number of channels is corrected using a frequency shift amount δf(t) with respect to the set classification d, and a demodulated beat signal is obtained.

[0109] The MIMO modulation signal generation unit 21a and the signal receiving unit 31 constitute the signal generation / receiving unit 400a. The modulation control unit 22a, demodulation unit 32a, range calculation unit 33, Doppler calculation unit 34, MIMO beamforming unit 35, and detection unit 36 ​​constitute the signal processing unit 500a. The signal processing unit 500a is implemented using a computer-based hardware configuration. The range calculation unit 33, the Doppler calculation unit 34, the MIMO beam forming unit 35, and the detection unit 36 ​​constitute the distance information acquisition unit and the velocity information acquisition unit.

[0110] Next, the operation of the radar device according to Embodiment 2 will be explained using the flowchart shown in Figure 15. In step ST1a, the modulation control unit 22a controls the frequency shift amount δf(t) and the time shift amount T SFT This will be set.

[0111] The frequency shift amount δf(t) is the frequency shift amount δf(t) calculated according to (7) above for any one of the classifications d set from classification I to classification III. Classification d is set by the modulation control unit 22 by determining the distance information detected by the radar receiver unit 300.

[0112] In step ST2a, the modulation signal generation unit 21a generates a signal whose frequency changes over time, and the pulse transmission interval T PRI A pulsed reference signal composed of multiple pulses having the following time shift amount T from the modulation control unit 22: SFT Using this, the time shift amount T SFT This generates a shifted, pulsed reference signal.

[0113] The modulation signal generation unit 21a generates transmission signals #1 to #N for any classification d set by the modulation control unit 22a from classification I to classification III, in which multiple pulses of the pulsed reference signal generated by the frequency shift amount δf(t) calculated in (7) above are given the frequency shift amount δf(t).

[0114] The modulation signal generation unit 21a generates transmission signals #1 to #N and transmits them to the corresponding transmission antennas 111 to 11 N Output to [this location]. In step ST3, the transmission signals #1 to #N from the modulation signal generation unit 21 are input to the transmitting antennas 111 to 11. N Each emits (transmits) a transmitted wave into space based on transmission signals #1 to #N.

[0115] In step ST4, multiple receiving antennas 121-12 M The transmitting antenna is 111~11 N The transmitted wave radiated into space is reflected by the target, the reflected wave is received as a received wave, and the received wave is converted into a received signal (reflected signal) #1 to #M.

[0116] In step ST5, receiving antennas 121-12 M The signal receiving unit 31, upon receiving signals #1 to #M from the input, performs AD conversion on each of the input received signals #1 to #M, performs frequency conversion, and outputs a beat signal. For each of the received signals #1 to #M, the corresponding received signals #11 to #M1, ~, and #1N to #MN have a frequency shift amount δf(t) shifted relative to one of the classifications d set from classification I to classification III given to the received signals #1 to #N.

[0117] Since each of the received signals #11 to #M1, ~, and #1N to #MN corresponding to the transmitted signals #1 to #N is given a frequency shift amount δf(t) for one of the classifications d set from classification I to classification III, whether the distance to the target is short or long, the beat signals of the transmitted chirp signal pulse and the corresponding received chirp signal pulse have their cross-correlation components for each PRF suppressed on the beat spectrum due to pulsation, making them less susceptible to interference by cross-correlation components.

[0118] In step ST6a, the demodulation unit 32a, which receives the beat signal from the signal receiving unit 31, corrects the frequency of the beat signal input from the signal receiving unit 31 using the frequency shift amount δf(t) given to each transmission signal #1 to #N for each (N × M) receiving channel relative to the output from the signal receiving unit 31, and demodulates it to obtain a demodulated beat signal. Steps ST7 to ST10 are the same as steps ST7 to ST10 in the radar device according to Embodiment 1, so their explanation will be omitted.

[0119] The radar system according to Embodiment 2 is a radar system using the TS-MIMO method in the FM-ICW system, wherein the radar transmitter 200a is a transmitting signal that repeats a transmitting chirp signal composed of multiple pulses with a pulse transmission interval whose frequency changes over time, and the transmitting signal is output with a time shift amount set for multiple transmitting antennas, by applying a frequency shift amount δf(t) for one of the multiple classifications d of the distance to the target to the multiple pulses in the transmitting chirp signal, so that when the radar receiver 300a generates a beat signal, there is overlap between the pulses of the transmitting chirp signal of the corresponding transmitting signal and the pulses of the receiving chirp signal of the receiving signal, and even if there are pulse loss in the pulses of the receiving chirp signal, the beat signal is less susceptible to interference from the cross-correlation components for each PRF on the beat spectrum due to pulsation. As a result, distance information is obtained that suppresses the degradation of SNR and reduces the increase in angle measurement errors over a wide range of distances to the target.

[0120] Embodiment 3. A radar device according to Embodiment 3 will be described with reference to Figures 16 to 18. The radar system according to Embodiment 3 is a radar system using the TS-MIMO method in the FM-ICW system, and for the transmission signals to multiple transmission channels, the sweep bandwidth B of the transmission chirp signal and the pulse width T of the transmission chirp signal are used. PLS and the number of pulses N in the transmitted chirp signal HITThe shift coefficient N calculated by SFT (=N HIT / (B×T PLS The time shift amount T set for the transmission channel using )) SFT (=T PRI ×N SFT It is characterized by having and outputting ). Therefore, the following description will focus on the features of the radar device according to Embodiment 3. In Figures 16 to 18, the same reference numerals as those used in Figures 1 to 13 indicate the same or corresponding parts.

[0121] As shown in Figure 16, the radar device according to Embodiment 3 comprises an antenna unit 100, a radar transmission unit 200b, and a radar reception unit 300b. The radar transmitter 200b is a transmission signal #1 to #N which is a transmission chirp signal consisting of multiple pulses with a pulse transmission interval whose frequency changes over time, and multiple transmission antennas 111 to 11 N In other words, the transmission signals #1 to #N for the transmission channel are transmitted to multiple transmission antennas 111 to 111 N Shift coefficient N SFT Time shift amount T set using SFT It outputs with the following characteristics.

[0122] The radar transmission unit 200b includes a MIMO modulation signal generation unit 21b and a modulation control unit 22b. The modulation control unit 22b controls the time shift amount T for multiple transmission signals #1 to #N. SFT Set it. Time shift amount T SFT This represents the amount of time shift between preceding and succeeding transmitted signals, for example, the amount of time shift between the output start time of transmitted signal #1 and the output start time of transmitted signal #2.

[0123] Time shift amount T SFT This is set by the value at which the cross-correlation value, which is the strength of the cross-correlation component, falls below a threshold. In other words, time shift amount T SFTis the shift coefficient N, which is the smallest integer value among the values where the cross-correlation value is less than or equal to the threshold value SFT is set using this value

[0124] The time shift amount T SFT is represented by the above equation (5). The time shift amount T SFT The shift coefficient N for SFT is represented by the above equation (6). That is, the shift coefficient N SFT is the coefficient for the time shift amount T PRI represented by the pulse transmission interval T SFT [[ID=!]] At this time, the shift coefficient N is N SFT is represented by N HIT / (B × T PLS ).

[0125] Here, the relationship between the time shift amount T SFT and the cross-correlation value will be explained. When there is no overlap between the pulses of the transmitted chirp signal and the received chirp signal, and there is no pulse dropout in the pulses of the received chirp signal, and the distance to the target is medium, the pulses of the transmitted chirp signal in the transmitted signal, as shown in FIG. 7, have a bandwidth that is the reciprocal of the pulse width 1 / T PLS and become a spectrum called a sinc function with a bandwidth of 1 / T PLS in the frequency domain. The sinc function is the function shown in FIG. 17 and, in FIG. 8, is the shape of the envelope due to pulsing.

[0126] In FIG. 8, only the main lobe of the envelope due to pulsing is shown. The cross-correlation value depends on the size of the envelope. The cross-correlation value decreases as the time shift amount T SFT increases. For example, in FIG. 8, the beat signal shown as "transmission 2, demodulation 1" shifts to the left side of FIG. 图示8, and thus the cross-correlation component generated in the beat signal shown as "transmission 1, demodulation 1" becomes smaller.

[0127] The shape of the envelope depends on the time shift amount TSFT The shift coefficient N becomes larger, that is, SFT When it gets bigger, it gets smaller. Figure 17 shows the shift coefficient N SFT This shows the relationship between the cross-correlation value and the shift coefficient N. SFT As the coefficient increases, the cross-correlation value decreases.

[0128] Therefore, in Embodiment 3, when the distance to the target shown in Figure 17 is a medium distance, the threshold for the cross-correlation value is set to -20 dB or less, and the shift coefficient N that shows -20 dB or less is set. SFT The smallest integer value among them, "3", is shifted by the N factor. SFT Let's assume that. While the threshold for cross-correlation was set at -20dB, it is not limited to -20dB. In both short-range and long-range cases, the shift coefficient N is the smallest integer value among those that show the cross-correlation value to be below the threshold, just as in the case of medium-range cases. SFT Using the time shift amount T SFT This is set by the modulation control unit 22b.

[0129] The MIMO modulation signal generation unit 21b has a sweep repetition period T WRI From a continuous reference signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, the pulse transmission interval T PRI Multiple (N) HIT It generates a pulsed reference signal composed of individual pulses.

[0130] The MIMO modulation signal generation unit 21 uses the pulsed reference signal as the transmit chirp signal, and the modulation control unit 22 sets a time shift amount T for the transmit chirp signals in transmit signals #1 to #N. SFT Provided, transmitting antenna 111~11 N The transmission signals #1 to #N are output sequentially to the corresponding transmission channel.

[0131] Time shift amount T set by the modulation control unit 22 SFTThe shift coefficient N, expressed by equation (6) above, is the smallest integer value among the values ​​in which the cross-correlation value is less than or equal to the threshold. SFT This is the value calculated using the above equation (5). As a result, the MIMO modulation signal generation unit 21 generates the transmitting antennas 111-11 N The time shift amount T set in accordance with this setting. SFT2 ~T SFTN The transmitted chirp signal output based on this is swept with a repetition period T. WRI Each of the repeated transmission signals #1 to #N is transmitted using the corresponding transmitting antennas 111 to 11 N Output to [this location].

[0132] The radar receiver 300b has multiple transmitting antennas 111-11 N Multiple receiving antennas 121-12 receive the transmitted waves from the radar transmitter 200b, transmitted signals #1-#N, which have been reflected by the target. M The system receives a received signal that repeats a received chirp signal composed of multiple pulses corresponding to the transmitted chirp signals #1 to #N. It generates a beat signal with a frequency that is the difference between the frequencies of the pulses of the transmitted chirp signals #1 to #N and the pulses of the received chirp signal of the received signal, thereby obtaining distance information. Multiple transmitting antennas 111-11 N and multiple receiving antennas 121-12 M Therefore, each receiving antenna 121~12 M Since it has N receiving channels, the output from the radar receiver 300 has (N × M) receiving channels.

[0133] The radar receiver 300b includes a signal receiving unit 31, a range calculation unit 33, a Doppler calculation unit 34, a MIMO beamforming unit 35, and a detection unit 36. The signal receiving unit 31 has multiple receiving antennas 121-12 M The received signals #1 to #M from each device are converted from analog to digital (AD), their frequencies are converted, they are converted into beat signals, and these beat signals are output.

[0134] Each of the received signals #1 to #M has N received signals corresponding to each of the transmitted signals #1 to #N, and the signal receiving unit 31 forms (M × N) receiving channels as its output. Since the signal processing for each of the received signals #1 to #M is essentially the same, we will primarily explain received signal #1 to avoid unnecessary complexity.

[0135] When the signal receiving unit 31 converts the received signal #1 into a beat signal, the time shift amount T is assigned to the transmitted signals #1 to #N relative to the received signals #11 to #1N in the received signal #1. SFT At the appropriate timing, a reference signal is generated, which is a mix of the corresponding transmitted signals #1 to #N and received signals #11 to #1N, and converted into a beat signal.

[0136] At this time, each of the transmitted signals #2 to #N has a set shift coefficient N. SFT The time shift amount T calculated using SFT Since it is output with a shift coefficient N set for each of the received signals #12 to #1N in received signal #1 and transmitted signals #2 to #N. SFT The time shift amount T calculated using SFT This is a received signal that has [a certain characteristic].

[0137] As a result, the cross-correlation value between the pulses of the transmitted chirp signal and the corresponding pulses of the received chirp signal is below a threshold, so there are no cross-correlation components with matching beat frequencies, and the beat signal is no longer interfered with by these cross-correlation components. In other words, the shift coefficient N is the smallest integer value among the values ​​that show the cross-correlation value to be below a threshold. SFT Time shift amount T set using SFT Because the received signal has this property, the shape of the envelope on the beat spectrum is changed, causing the cross-correlation component to shift on the beat spectrum, thus reducing interference from the cross-correlation component in the beat signal.

[0138] The beat signal output from the signal receiving unit 31 is supplied to the range calculation unit 33. The range calculation unit 33, the Doppler calculation unit 34, the MIMO beamforming unit 35, and the detection unit 36 constitute a distance information acquisition unit. Also, the range calculation unit 33, the Doppler calculation unit 34, the MIMO beamforming unit 35, and the detection unit 36 constitute a speed information acquisition unit.

[0139] Next, the operation of the radar apparatus according to Embodiment 3 will be described using the flowchart shown in FIG. 18. In step ST1b, the modulation control unit 22 sets the time shift amount T SFT is set. The time shift amount T SFT is set using the shift coefficient N SFT for each of the plurality of transmission channels. The shift coefficient N SFT is, for example, the smallest integer value among the values indicating that the cross-correlation value is below the threshold for each of the classifications from Classification I to Classification III.

[0140] In step ST2b, the modulation signal generation unit 21a generates a transmitted chirp signal composed of a pulsed reference signal composed of a plurality of pulses whose frequency changes over time and has a pulse transmission interval T PRI using the time shift amount T SFT set to the time shift amount set by the modulation control unit 22 for any one of the classifications d from Classification I to Classification III, for example, and sequentially shifts the time shift amount T SFT to generate transmission signals #1 to #N, and outputs each of the transmission signals #1 to #N to the corresponding transmission antennas 111 to 11 N .

[0141] In step ST3, the transmission antennas 111 to 11 N to which the transmission signals #1 to #N from the modulation signal generation unit 21 are input each radiate (transmit) a transmission wave by the transmission signals #1 to #N into space. In step ST4, the plurality of reception antennas 121 to 12 M are the transmission antennas 111 to 11 NThe transmitted wave radiated into space is reflected by the target, the reflected wave is received as a received wave, and the received wave is converted into a received signal (reflected signal) #1 to #M.

[0142] In step ST5, receiving antennas 121-12 M The signal receiving unit 31, upon receiving signals #1 to #M, performs AD conversion on each of the received signals #1 to #M, performs frequency conversion, outputs a beat signal to the range calculation unit 33, and proceeds to step ST7. Steps ST7 to ST10 are the same as steps ST7 to ST10 in the radar device according to Embodiment 1, so their explanation will be omitted.

[0143] The radar system according to Embodiment 3 is a radar system using the TS-MIMO method in the FM-ICW system, wherein the radar transmitter 200b is a transmitting signal that repeats a transmitting chirp signal composed of multiple pulses having a pulse transmission interval and whose frequency changes over time, and the transmitting signal to multiple transmitting antennas is output with a time shift amount set using a shift coefficient calculated using the sweep bandwidth of the transmitting chirp signal, the pulse width of the pulses of the transmitting chirp signal, and the number of pulses of the transmitting chirp signal, which are given to each of the multiple transmitting antennas, so that when the radar receiver 300b generates a beat signal, even if there is overlap between the pulses of the transmitting chirp signal of the corresponding transmitting signal and the pulses of the receiving chirp signal of the receiving signal, and even if there are pulse loss in the pulses of the receiving chirp signal, the beat signal is less susceptible to interference from the cross-correlation components for each PRF on the beat spectrum due to pulsation. As a result, distance information is obtained that suppresses the degradation of SNR and reduces the increase in angle measurement errors over a wide range of distances to the target.

[0144] Another example 1. In the radar device according to Embodiment 1, the time shift amount T is set using a shift coefficient calculated from the sweep bandwidth of the transmitted chirp signal, the pulse width of the pulses of the transmitted chirp signal, and the number of pulses of the transmitted chirp signal, which are given to each of the multiple transmission channels described in the radar device according to Embodiment 3. SFT Using this, sequential time shift amount T SFT The shifted transmission signals #1 to #N are transmitted to corresponding transmitting antennas 111 to 11 N A technique for outputting to this can also be applied.

[0145] In other words, in Figure 1, which shows the radar device according to Embodiment 1, the MIMO modulation signal generation unit 21 and the modulation control unit 22 in the radar transmission unit 200 are modified as follows. The modulation control unit 22 calculates the phase change amount φ for each pulse in the transmitted chirp signals #1 to #N for the transmitted channel, according to equation (1) above, for one of the classifications d from classification I to classification III. h Set it. The modulation control unit 22 applies a shift coefficient N to the transmitted chirp signals #1 to #N for the transmitting channel. SFT Set the time shift amount T for the transmitted signals #1 to #N based on the set shift coefficient. SFT Set it.

[0146] setting shift coefficient N SFT The sweep bandwidth B of the transmitted chirp signal and the pulse width T of the transmitted chirp signal are expressed by equation (6) above. PLS and the number of pulses N in the transmitted chirp signal HIT It is calculated using and is the smallest integer value among the values ​​in which the cross-correlation value for any one of classifications d from classification I to classification III is less than or equal to the threshold. Time shift amount T SFT The shift coefficient N is the smallest integer value among the values ​​that show the cross-correlation value to be less than or equal to a threshold for any one of classifications d from classification I to classification III. SFT It is set using the above equation (5).

[0147] The MIMO modulation signal generation unit 21 has a sweep repetition period T WRI From a continuous reference signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, the pulse transmission interval T PRI Multiple (N) HIT It generates a pulsed reference signal composed of individual pulses.

[0148] The MIMO modulation signal generation unit 21 modulates the pulsed reference signal with respect to the time shift amount T set by the modulation control unit 22. SFT Based on this, transmitting antenna 111~11 N Sequential time shift amount T for the corresponding transmission channel SFT The modulation control unit 22 shifts the phase change amount φ for one of the classifications d from classification I to classification III. h Based on this, transmitting antenna 111~11 N Each of the multiple pulses of the corresponding pulsed reference signal has a phase change amount φ h Generates a transmitted chirp signal based on the given input.

[0149] The MIMO modulation signal generation unit 21 is connected to the transmitting antennas 111-11 N The time shift amount T set in accordance with this setting. SFT The transmitted chirp signal output based on this is swept with a repetition period T. WRI Each of the repeated transmission signals #1 to #N is transmitted using the corresponding transmitting antennas 111 to 11 N Output to [this location].

[0150] The processing performed by the radar receiver 300 is the same as the processing performed by the radar receiver 300 in the radar device according to Embodiment 1. The radar device according to another embodiment 1 has a phase change amount φ for any one of classifications d from classification I to classification III. hInterference due to cross-correlation components is further reduced by using the transmitted signal applied to each pulse of the transmitted chirp signal, thereby suppressing the cross-correlation component for each PRF on the beat spectrum by pulsing the beat signal, and by outputting with a time shift amount set using a shift coefficient which is the smallest integer value among the values ​​in which the cross-correlation value is below a threshold for each of the multiple transmitted signals, thereby suppressing the cross-correlation component for each PRF on the beat spectrum by pulsing the beat signal.

[0151] Another example 2. In the radar device according to Embodiment 2, the time shift amount T is set using a shift coefficient calculated from the sweep bandwidth of the transmitted chirp signal, the pulse width of the pulses of the transmitted chirp signal, and the number of pulses of the transmitted chirp signal, which are given to each of the multiple transmission channels described in the radar device according to Embodiment 3. SFT Using this, sequential time shift amount T SFT The shifted transmission signals #1 to #N are transmitted to corresponding transmitting antennas 111 to 11 N A technique for outputting to this can also be applied.

[0152] In other words, in Figure 14, which shows the radar device according to Embodiment 2, the MIMO modulation signal generation unit 21a and the modulation control unit 22a in the radar transmission unit 200a are modified as follows. The modulation control unit 22a transmits the chirp signals #1 to #N for the transmit channel. For each pulse in the circuit, a frequency shift amount δf(t) calculated by equation (7) above is set for one of the classifications d from classification I to classification III. The modulation control unit 22a applies a shift coefficient N to the transmitted chirp signals #1 to #N for the transmitting channel. SFT Set the time shift amount T for the transmitted signals #1 to #N based on the set shift coefficient. SFT Set it.

[0153] setting shift coefficient N SFTThe sweep bandwidth B of the transmitted chirp signal and the pulse width T of the transmitted chirp signal are expressed by equation (6) above. PLS and the number of pulses N in the transmitted chirp signal HIT It is calculated using and is the smallest integer value among the values ​​in which the cross-correlation value for any one of classifications d from classification I to classification III is less than or equal to the threshold. Time shift amount T SFT The shift coefficient N is the smallest integer value among the values ​​that show the cross-correlation value to be less than or equal to a threshold for any one of classifications d from classification I to classification III. SFT It is set using the above equation (5).

[0154] The MIMO modulation signal generation unit 21a has a sweep repetition period T WRI From a continuous reference signal whose frequency changes over time from the minimum transmission frequency fc to the sweep bandwidth B, the pulse transmission interval T PRI Multiple (N) HIT It generates a pulsed reference signal composed of individual pulses.

[0155] The MIMO modulation signal generation unit 21a modulates the pulsed reference signal with respect to the time shift amount T set by the modulation control unit 22. SFT Based on this, transmitting antenna 111~11 N Sequential time shift amount T for the corresponding transmission channel SFT The frequency is shifted, and based on the frequency shift amount δf(t) for one of the classifications d from classification I to classification III set by the modulation control unit 22, the transmitting antennas 111~11 N A transmit chirp signal is generated by applying a frequency shift amount δf(t) to multiple pulses of the corresponding pulsed reference signal.

[0156] The MIMO modulation signal generation unit 21a is connected to the transmitting antennas 111-11 N The time shift amount T set in accordance with this setting. SFT The transmitted chirp signal output based on this is swept with a repetition period T. WRI Each of the repeated transmission signals #1 to #N is transmitted using the corresponding transmitting antennas 111 to 11 N Output to [this location].

[0157] The processing performed by the radar receiver 300a is the same as the processing performed by the radar receiver 300a in the radar device according to Embodiment 2. In the radar device according to another embodiment 2, interference due to cross-correlation components is further reduced by suppressing the cross-correlation component for each PRF on the beat spectrum through pulsation of the beat signal by using a transmitted signal to which a frequency shift amount δf(t) for any one of classifications d from classification I to classification III is applied to the transmitted chirp signal, and by outputting multiple transmitted signals with a time shift amount set using a shift coefficient which is the smallest integer value among the values ​​in which the cross-correlation value is less than or equal to a threshold, thereby suppressing the cross-correlation component for each PRF on the beat spectrum through pulsation of the beat signal.

[0158] Furthermore, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component of each embodiment. [Industrial applicability]

[0159] The radar system described herein can be applied to high-frequency surface wave radar for long-range ocean surveillance and automotive radar using decameter waves, among others. [Explanation of Symbols]

[0160] 100 Antenna section, 111~11 N Transmitting antenna, 121~12 M Receiving antenna, 200, 200a, 200b; Radar transmitting unit, 21, 21a, 21b; MIMO modulated signal generation unit, 22, 22a, 22b; Modulation control unit, 300, 300a, 300b; Radar receiving unit, 31; Signal receiving unit, 32, 32a; Demodulation unit, 33; Range calculation unit, 34; Doppler calculation unit, 35; MIMO beam forming unit, 36; Detection unit.

Claims

1. A radar transmitter unit that outputs a transmission chirp signal consisting of multiple pulses with a pulse transmission interval whose frequency changes over time, and which applies a phase change amount to each of the multiple pulses in the transmission chirp signal for one of several classifications based on the distance to the target, and has a time shift amount. A radar receiver receives a received signal that repeats a received signal composed of multiple pulses corresponding to multiple pulses of the transmission chirp signal of the transmission signal from multiple receiving antennas, which receive a received wave that is the transmitted wave from the radar transmitter unit from multiple transmitting antennas reflected by the target, and generates a beat signal having a frequency that is the difference between the frequencies of the corresponding pulses of the transmission chirp signal of the transmission signal and the pulses of the received chirp signal of the received signal, thereby obtaining distance information corresponding to the distance to the target. A radar device equipped with [a specific feature / feature].

2. The radar transmission unit has a modulation signal generation unit and a modulation control unit. The radar device according to claim 1, wherein the transmission signal corresponding to the plurality of transmitting antennas is a pulsed reference signal composed of a plurality of pulses whose frequency changes over time and which have a pulse transmission interval, which is pulsed by the modulation signal generation unit, and the time shift amount is shifted according to the plurality of transmitting antennas based on a time shift amount set by the modulation control unit, and a phase change amount is given to each of the plurality of pulses of the pulsed reference signal based on a phase change amount in the classification set by the modulation control unit, and the transmission chirp signal is repeated at a sweep repetition period.

3. The radar receiver unit has a signal receiving unit, a demodulation unit, and a speed information acquisition unit. The beat signal is generated when the signal receiving unit receives signals from the plurality of receiving antennas, converts the received signals from analog to digital, converts the frequency, and converts them into a beat signal with the corresponding digital signal of the transmitted signal. The demodulation unit corrects the beat signal generated by the signal receiving unit by applying the phase change amount given to the transmitted signal to the beat signal, thereby obtaining a demodulated beat signal. The distance information is obtained by performing a Fourier transform on the beat signal demodulated by the demodulation unit and executing a target detection process. The radar device according to claim 1.

4. A radar transmitter unit outputs a transmission chirp signal consisting of multiple pulses with a pulse transmission interval whose frequency changes over time, and which is repeated over time. The transmission signal for multiple transmitting antennas is given a frequency shift amount for one of several classifications based on the distance to the target, and is output with a time shift amount. A radar receiver receives a received signal that repeats a received signal composed of multiple pulses corresponding to multiple pulses of the transmission chirp signal of the transmission signal from multiple receiving antennas, which receive a received wave that is the transmitted wave from the radar transmitter unit from multiple transmitting antennas reflected by the target, and generates a beat signal having a frequency that is the difference between the frequencies of the corresponding pulses of the transmission chirp signal of the transmission signal and the pulses of the received chirp signal of the received signal, thereby obtaining distance information corresponding to the distance to the target. A radar device equipped with [a specific feature / feature].

5. The radar transmission unit has a modulation signal generation unit and a modulation control unit. The radar device according to claim 4, wherein the transmission signal corresponding to the plurality of transmitting antennas is a pulsed reference signal composed of a plurality of pulses whose frequency changes over time and which have a pulse transmission interval, which is pulsed by the modulation signal generation unit, and the time shift amount is shifted according to the plurality of transmitting antennas based on a time shift amount set by the modulation control unit, and the transmission chirp signal to which the plurality of pulses of the pulsed reference signal are given a frequency shift amount based on a frequency shift amount in the classification set by the modulation control unit is repeated at a sweep repetition period.

6. The radar receiver unit has a signal receiving unit, a demodulation unit, and a speed information acquisition unit. The beat signal is generated when the signal receiving unit receives signals from the plurality of receiving antennas, converts the received signals from analog to digital, converts the frequency, and converts them into a beat signal with the corresponding digital signal of the transmitted signal. The demodulation unit corrects the beat signal generated by the signal receiving unit using the frequency shift amount applied to the transmitted signal relative to the beat signal, and obtains a demodulated beat signal. The distance information is obtained by performing a Fourier transform on the beat signal demodulated by the demodulation unit and executing a target detection process. The radar device according to claim 4.

7. The radar device according to any one of claims 1 to 6, wherein the multiple classifications based on the distance to the target are: a classification corresponding to medium distance where the pulses of the transmitted chirp signal and the pulses of the received chirp signal do not overlap; a classification corresponding to short distance which is closer than the classification corresponding to medium distance; and a classification corresponding to long distance which is further than the classification corresponding to medium distance.

8. The radar apparatus according to any one of claims 1 to 6, wherein the time shift amount for a transmission signal that the radar transmitting unit outputs to the plurality of transmitting antennas sequentially with a time shift amount is a time shift amount set using a shift coefficient calculated from the sweep bandwidth of the transmission chirp signal, the pulse width of the pulses of the transmission chirp signal, and the number of pulses of the transmission chirp signal, which is given to the plurality of transmitting antennas.

9. A radar transmitter outputs a transmission signal that repeats a transmission chirp signal consisting of multiple pulses having a pulse transmission interval, the frequency of which changes over time, and the transmission signal to multiple transmitting antennas having a time shift amount set using a shift coefficient calculated using the sweep bandwidth of the transmission chirp signal, the pulse width of the pulses of the transmission chirp signal, and the number of pulses of the transmission chirp signal. A radar receiver receives a received signal that repeats a received signal composed of multiple pulses corresponding to multiple pulses of the transmission chirp signal of the transmission signal from multiple receiving antennas, which receive a received wave that is the transmitted wave from the radar transmitter unit from multiple transmitting antennas reflected by the target, and generates a beat signal having a frequency that is the difference between the frequencies of the corresponding pulses of the transmission chirp signal of the transmission signal and the pulses of the received chirp signal of the received signal, thereby obtaining distance information corresponding to the distance to the target. A radar device equipped with [a specific feature / feature].

10. The radar device according to claim 9, wherein the shift coefficient is the smallest integer value among the values ​​in which the cross-correlation value, which is the intensity of the cross-correlation component for each pulse repetition frequency on the beat spectrum due to pulsation occurring in the beat signal of the corresponding pulse of the transmitted chirp signal of the transmitted signal and the pulse of the received chirp signal of the received signal, is less than or equal to a threshold.

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