Radar system

Abstract

To improve the detection resolution of targets in a radar system that includes two radar units.SOLUTION: Each of transmitting and receiving antennas 21 and 31 is arranged in a sensor housing 10 so that multiple antenna elements that make up each antenna are axial-symmetrical with respect to a reference line BL. In addition, each of the transmitting and receiving antennas 21 and 31 is arranged so that a distance DL between the center locations of each of the transmitting and receiving antennas 21 and 31 is 2 to 3 times as much as an antenna aperture length of each of the transmitting and receiving antennas 21 and 31. A control unit 50 generates a bistatic antenna between the transmitting and receiving antennas 21 and 31 based on a reception result at one of the transmitting and receiving antennas 21 and 31 of a reflected wave from a target that was transmitted from the other. The control unit 50 detects the target based on the reception result of the reflected wave from the target at the first transmitting and receiving antenna 21, the second transmitting and receiving antenna 31, and the bistatic antenna.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to a radar device.

Background Art

[0002] Patent Document 1 and Non-Patent Document 1 disclose a configuration in which two non-coherent radar units spatially separated from each other transmit and receive radio waves to and from each other via substantially the same radio channel. In such a configuration, a virtual antenna (bistatic antenna) can be generated at the center between the units, where the antenna aperture length is twice that of the antennas provided in each unit, thereby enhancing the azimuth resolution.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​However, in the conventional radar system, even if coherent measurement is theoretically possible with two radar units, the antenna aperture length of the virtual antenna is only expanded to twice the antenna aperture length of the antenna provided in each unit, so there is still room for improvement in the target detection resolution of the radar system.

[0006] An object of the present disclosure is to improve the detection resolution of a target in a radar device including two radar units. [Means for solving the problem]

[0007] The invention described in claim 1 is A radar device that detects targets using radio waves, A sensor housing (10); a first radar unit (20) including a first transmitting / receiving antenna (21) for transmitting and receiving radio waves; a second radar unit (30) including a second transmitting / receiving antenna (31) for transmitting and receiving radio waves; a control unit (50) that detects a target based on reception results of a reflected wave reflected from the target at each of the first transmitting / receiving antenna and the second transmitting / receiving antenna, When a virtual line that is equidistant from a first position (P1), which is the center position of the first transmitting / receiving antenna in the arrangement direction of the first transmitting / receiving antenna and the second transmitting / receiving antenna, and a second position (P2), which is the center position of the second transmitting / receiving antenna in the arrangement direction, is defined as a reference line (BL), the first transmitting / receiving antenna and the second transmitting / receiving antenna are arranged on the sensor housing such that the multiple antenna elements constituting each are symmetrical with respect to a reference line, and are arranged such that the distance (DL) from the first position to the second position is not less than two times and not more than three times the antenna aperture length (PL2) of the first transmitting / receiving antenna and the second transmitting / receiving antenna, The control unit generates a bistatic antenna including multiple virtual antenna elements between the first and second transmitting / receiving antennas based on a reception result at the other antenna of a reflected wave of a radio wave transmitted from one of the first and second transmitting / receiving antennas, which is reflected by a target, and detects the target based on a reception result at the first and second transmitting / receiving antennas, the second transmitting / receiving antenna, and the bistatic antenna of the reflected wave reflected by the target.

[0008] In this way, if the first radar unit and the second radar unit are configured to be arranged in the same sensor housing, the first transmitting / receiving antenna and the second transmitting / receiving antenna can be arranged close to each other. If the central positions of the transmitting / receiving antennas are arranged at a distance of about two to three times the antenna aperture length of each transmitting / receiving antenna, a virtual array antenna in which the first transmitting / receiving antenna, the bistatic antenna, and the second transmitting / receiving antenna are arranged in succession can be realized. This virtual array antenna includes not only the bistatic antenna but also the transmitting / receiving antennas provided in each unit, so that the antenna aperture length can be made larger than that of the bistatic antenna. In this way, according to the radar device disclosed herein, an antenna aperture length more than twice that of each transmitting / receiving antenna provided in each unit can be realized. Therefore, it is possible to improve the detection resolution of targets compared to the conventional technology.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a radar device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic configuration diagram of a first radar unit and a second radar unit. [Diagram 3] FIG. 2 is an explanatory diagram for explaining an antenna configuration of a radar device. [Figure 4]FIG. 1 is an explanatory diagram of a bistatic antenna. [Diagram 5] FIG. 2 is an explanatory diagram for explaining a method for distinguishing between a received signal on a direct path and a received signal on a cross path in the radar device according to the first embodiment. [Figure 6] 4 is an explanatory diagram for explaining the frequency band of an IF signal obtained in a direct path mode and the frequency band of an IF signal obtained in a cross path mode according to the first embodiment. FIG. [Figure 7] FIG. 11 is an explanatory diagram for explaining a cutoff frequency and a sampling frequency in a direct path mode and a cross path mode in a radar device according to a second embodiment. [Figure 8] FIG. 11 is an explanatory diagram for explaining a method for distinguishing between a signal received on a direct path and a signal received on a cross path in a radar device according to a second embodiment. [Figure 9] 11 is an explanatory diagram for explaining the frequency band of an IF signal obtained in a direct path mode and the frequency band of an IF signal obtained in a cross path mode according to the second embodiment. FIG. [Figure 10] FIG. 11 is an explanatory diagram for explaining a method for distinguishing between a signal received on a direct path and a signal received on a cross path in a radar device according to a third embodiment. [Figure 11] FIG. 11 is an explanatory diagram for explaining the frequency band of an IF signal obtained in a direct path mode and the frequency band of an IF signal obtained in a cross path mode according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0012] (First embodiment) The present embodiment will be described with reference to Fig. 1 to Fig. 6. In the present embodiment, an example will be described in which a radar device 1 according to the present disclosure is mounted on a vehicle and applied to a target detection device that detects targets such as other vehicles and stationary objects present around the vehicle as targets.

[0013] The radar device 1 emits radio waves ahead of the vehicle and receives radio waves reflected by a target ahead of the vehicle to determine the distance to the target, the relative speed with respect to the vehicle, the direction with respect to the vehicle, etc.

[0014] The radar device 1 employs the FMCW method as a signal modulation method. The radar device 1 operates at a radio frequency in a frequency band corresponding to millimeter waves (e.g., 76 GHz). Note that the operating frequency of the radio waves transmitted and received by the radar device 1 is not limited to a frequency corresponding to millimeter waves, and may be a frequency other than millimeter waves.

[0015] 1, the radar device 1 includes a sensor housing 10, a first radar unit 20, a second radar unit 30, and a control unit 50. For convenience, in the drawings, the first radar unit 20 may be referred to as "RU1" and the second radar unit 30 may be referred to as "RU2."

[0016] The sensor housing 10 is a member that constitutes the outer shell of the radar device 1. The sensor housing 10 is provided with a first radar unit 20, a second radar unit 30, and a control unit 50. Note that the control unit 50 may be provided outside the sensor housing 10.

[0017] 2, the first radar unit 20 is a sensor unit including a first transmission / reception antenna 21 that transmits and receives radio waves. In addition to the first transmission / reception antenna 21, the first radar unit 20 includes a first transmission unit 22 and a first reception unit 23. The first radar unit 20 is configured such that the first transmission unit 22 and the first reception unit 23 are mounted on a single semiconductor chip.

[0018] As shown in FIG. 3, the first transmitting / receiving antenna 21 has a real array antenna consisting of a plurality of transmitting antennas Tx and a plurality of receiving antennas Rx. The real array antenna in this example includes three transmitting antennas Tx and four receiving antennas Rx. Specifically, in the real array antenna, the four receiving antennas Rx are arranged at equal intervals at a predetermined reference distance, and the three transmitting antennas Tx are arranged at equal intervals at a distance that is four times the reference distance. The reference distance is set to, for example, a half wavelength of radio waves. The first transmitting / receiving antenna 21 of the present disclosure does not only mean a real array antenna consisting of real antenna elements, but can be interpreted as a virtual array antenna including real antenna elements and virtual antenna elements. The same applies to the second transmitting / receiving antenna 31.

[0019] 2, the first transmitter 22 generates a chirp signal whose frequency changes continuously as a transmission signal, and transmits the generated transmission signal to each transmitting antenna Tx. The first transmitter 22 has a first local oscillator 221, a first distributor 222, a first transmitting amplifier 223, a first timing engine 224, and the like.

[0020] The first local oscillator 221 generates a transmission signal synchronized with a local signal. The first local oscillator 221 includes a local signal generator 221a that generates a local signal, a PLL circuit 221b that outputs a signal synchronized with the local signal, and a VCO circuit 221c that varies the frequency of the signal output by the PLL circuit 221b.

[0021] The first distributor 222 distributes a transmission signal to the first transmission amplifier 223 side and the first receiving unit 23 side. The first distributor 222 is connected to both the first transmission amplifier 223 and the first receiving unit 23.

[0022] The first transmitting amplifier 223 is provided between the first distributor 222 and each transmitting antenna Tx. The first transmitting amplifier 223 amplifies the power of the transmission signal and outputs it to the transmitting antenna Tx.

[0023] The first timing engine 224 controls the transmission output from the first transmitting unit 22 and the timing of the start of sampling in the first receiving unit 23. The first timing engine 224 is connected to be able to output a signal to the second timing engine 324 provided in the second transmitting unit 32 so that the transmission start timings of the chirp signals in each of the transmitting units 22, 32 can be synchronized.

[0024] The first receiving unit 23 generates a beat signal based on the reception signals received by each receiving antenna Rx, and transmits the beat signal to the control unit 50. The first receiving unit 23 includes a first receiving side amplifier 231, a first mixer 232, a first filter 233, a first AD converter 234, and the like.

[0025] The first receiving amplifier 231 generates a receiving signal by amplifying an RF signal generated by receiving a reflected wave reflected by a target at each receiving antenna Rx. This receiving signal is an electrical signal corresponding to the reflected wave received at each receiving antenna Rx.

[0026] The first mixer 232 executes direct detection processing (so-called IQ detection processing) on ​​the received signal based on the local signal generated by the first transmission unit 22. The first mixer 232 mixes the local signal and the received signal to generate an intermediate frequency signal (so-called IF signal) corresponding to the frequency difference between the two, and outputs the signal to the first filter 233. In the quadrature detection processing, it is possible to distinguish between positive and negative frequency components in the IF signal by using carrier waves that are orthogonal to each other. That is, the first mixer 232 of this embodiment is able to distinguish between positive and negative frequency components in the IF signal.

[0027] The first filter 233 is a low-pass filter having a predetermined cutoff frequency, and is a variable-frequency filter configured to be able to switch the cutoff frequency.

[0028] The first AD converter 234 is an AD conversion unit that converts the reception result of the reflected wave reflected by the target into a digital signal. The first AD converter 234 converts the IF signal, which is an analog signal, into a beat signal, which is a digital signal, and outputs it to the control unit 50. The first AD converter 234 is configured to be able to switch the sampling frequency.

[0029] Next, the second radar unit 30 will be described. The second radar unit 30 is a sensor unit including a second transmission / reception antenna 31 that transmits and receives radio waves. In addition to the second transmission / reception antenna 31, the second radar unit 30 includes a second transmission unit 32 and a second reception unit 33. The second radar unit 30 has a configuration in which the second transmission unit 32 and the second reception unit 33 are mounted on a single semiconductor chip.

[0030] The second transmission / reception antenna 31 has a plurality of transmission antennas Tx and a plurality of reception antennas Rx. In this example, the second transmission / reception antenna 31 has three transmission antennas Tx and four reception antennas Rx.

[0031] As shown in Fig. 3, the second transmitting / receiving antenna 31 has a real array antenna consisting of multiple transmitting antennas Tx and multiple receiving antennas Rx. The real array antenna in this example includes three transmitting antennas Tx and four receiving antennas Rx. Specifically, the real array antenna has four receiving antennas Rx arranged at equal intervals with a predetermined reference distance between them, and three transmitting antennas Tx arranged at equal intervals with a distance four times the reference distance between them.

[0032] 2, the second transmitter 32 generates a chirp signal whose frequency changes continuously as a transmission signal, and transmits the generated transmission signal to each transmitting antenna Tx. The second transmitter 32 has a second local oscillator 321, a second distributor 322, a second transmitting amplifier 323, a second timing engine 324, and the like.

[0033] The second local oscillator 321 is partially different from the first local oscillator 221. The second local oscillator 321 includes a PLL circuit 321b and a VCO circuit 321c. The second local oscillator 321 has the PLL circuit 321b connected to the local signal generating unit 221a of the first local oscillator 221.

[0034] This ensures clock synchronization in each of the local oscillators 221, 321. In addition, each of the local oscillators 221, 321 is provided with an individual PLL circuit 221b, 321b and VCO circuit 221c, 321c, making it possible to simultaneously generate transmission signals of different frequencies.

[0035] The second distributor 322 distributes the transmission signal to the second transmission-side amplifier 323 side and the second receiving unit 33 side. The second distributor 322 is connected to both the second transmission-side amplifier 323 and the second receiving unit 33.

[0036] The second transmission amplifier 323 is provided between the second distributor 322 and each transmission antenna Tx. The second transmission amplifier 323 amplifies the power of the transmission signal and outputs it to the transmission antenna Tx.

[0037] The second timing engine 324 controls the transmission output from the second transmitting unit 32 and the timing of the start of sampling in the second receiving unit 33. The second timing engine 324 is connected to the first timing engine 224 of the first transmitting unit 22 so that the transmission start timings of the chirp signals in each of the transmitting units 22, 32 can be synchronized. The second timing engine 324 functions as a delay circuit that delays the transmission timing of a transmission signal from the second transmission / reception antenna 31 relative to the transmission timing of a transmission signal from the first transmission / reception antenna 21. The delay time in the second timing engine 324 is set to a time that allows separation of the frequency band of an IF signal desired for one of the first transmission / reception antenna 21 and the second transmission / reception antenna 31 from the frequency band of an IF signal desired for the other when the transmission / reception antennas 21, 31 transmit and receive radio waves mutually. Note that, hereinafter, a mode in which one of the transmission / reception antennas 21, 31 transmits and receives radio waves is referred to as a "direct path mode," and a mode in which the transmission / reception antennas 21, 31 transmit and receive radio waves mutually is referred to as a "cross path mode."

[0038] The second receiving unit 33 generates a beat signal based on the reception signals received by each receiving antenna Rx, and transmits the beat signal to the control unit 50. The second receiving unit 33 includes a second receiving side amplifier 331, a second mixer 332, a second filter 333, a second AD converter 334, and the like.

[0039] The second mixer 332 performs direct detection processing (so-called IQ detection processing) on ​​the received signal based on the local signal generated by the second transmission unit 32. The second mixer 332 generates an IF signal by mixing the local signal and the received signal, and outputs the IF signal to the second filter 333.

[0040] The second filter 333 is a low-pass filter having a predetermined cutoff frequency, similar to the first filter 233. The second filter 333 employs a variable frequency filter configured to be able to switch the cutoff frequency.

[0041] The second AD converter 334 is an AD conversion unit that converts the reception result of the reflected wave reflected by the target into a digital signal. The second AD converter 334 converts the IF signal, which is an analog signal, into a beat signal, which is a digital signal, and outputs it to the control unit 50. The second AD converter 334 is configured to be able to switch the sampling frequency.

[0042] The control unit 50 is an electronic control device mainly composed of a microcomputer equipped with a processor and a memory. The memory is, for example, a ROM, a RAM, etc. Various functions of the microcomputer are realized by the processor executing a program stored in a non-transient physical storage medium.

[0043] The control unit 50 detects the distance to the target, the relative speed of the target, and the azimuth of the target based on the beat signals obtained from each unit 20, 30. The control unit 50 determines the distance to the target, for example, by performing frequency analysis of the beat signals using FFT. The control unit 50 performs FFT for each beat frequency component to determine the Doppler frequency and determines the relative speed of the target based on the Doppler frequency. Furthermore, the control unit 50 detects the azimuth of the target based on the fact that the phase of the received signal of each receiving antenna Rx differs depending on the angle of arrival of the reflected wave.

[0044] In addition, the control unit 50 performs signal processing on beat signals generated when radio waves are transmitted and received by each of the transmitting and receiving antennas 21, 31, thereby generating a virtual antenna having antenna elements several times the number of the actually existing receiving antenna Rx.

[0045] As shown in Fig. 3, each of the transmitting and receiving antennas 21 and 31 of this embodiment is configured as a MIMO antenna, which is a virtual antenna that utilizes MIMO technology. In a MIMO antenna, the antenna aperture length AL2 increases as the number of virtual antenna elements increases. Each of the transmitting and receiving antennas 21 and 31 of this embodiment has an antenna aperture length AL2 that is three times the antenna aperture length AL1 of each receiving antenna Rx. Note that MIMO is an abbreviation for Multi Input Multi Output. SIMO is an abbreviation for Single Input Multi Output.

[0046] Here, the reference line BL is defined as a virtual line that is equidistant from a first position P1, which is the center position of the first transmission / reception antenna 21, and a second position P2, which is the center position of the second transmission / reception antenna 31, in the arrangement direction of the first transmission / reception antenna 21 and the second transmission / reception antenna 31.

[0047] At this time, the first transmitting / receiving antenna 21 and the second transmitting / receiving antenna 31 are arranged on the sensor housing 10 so that the multiple antenna elements that constitute each are line-symmetrical with respect to the reference line BL.

[0048] In addition, the first transmitting / receiving antenna 21 and the second transmitting / receiving antenna 31 are arranged such that the distance DL from the first position P1 to the second position P2 is at least two times and at most three times the antenna aperture length AL2 of each of the transmitting / receiving antennas 21, 31. The first transmitting / receiving antenna 21 and the second transmitting / receiving antenna 31 in this example are arranged such that the distance DL from the first position P1 to the second position P2 is approximately 2.75 times the antenna aperture length AL2 of each of the transmitting / receiving antennas 21, 31 so that each of the transmitting / receiving antennas 21, 31 partially overlaps with a bistatic antenna, which will be described later.

[0049] On the premise of these, the control unit 50 generates a bistatic antenna between each of the transmitting and receiving antennas 21 and 31 based on the reception result at the other antenna of a reflected wave of a radio wave transmitted from one of the transmitting and receiving antennas 21 and 31, which is reflected by a target. The bistatic antenna is a virtual array antenna including a plurality of virtual antenna elements. As shown in FIG. 4, in the cross-path mode, a portion where the phases of the reflected waves match occurs at the center of each of the transmitting and receiving antennas 21 and 31, so that a bistatic antenna consisting of a plurality of virtual antenna elements can be generated at the center of each of the transmitting and receiving antennas 21 and 31. The principle of such a bistatic antenna is described in detail in Non-Patent Document 1, and therefore, a description thereof will be omitted in this specification.

[0050] The control unit 50 generates a first bistatic based on a reception result at one of the transmitting / receiving antennas 21, 31, for example, and generates a second bistatic based on a reception result at the other of the transmitting / receiving antennas 21, 31. The bistatic antenna in this example has an antenna configuration in which a virtual antenna element constituting the first bistatic and a virtual antenna element constituting the second bistatic overlap at the center of the bistatic antenna.

[0051] Furthermore, in this embodiment, the transmitting / receiving antennas 21, 31 are arranged such that the distance DL from the first position P1 to the second position P2 is approximately three times the antenna aperture length AL2 of each of the transmitting / receiving antennas 21, 31. As a result, the bistatic antenna has an antenna configuration in which virtual antenna elements at both ends of the bistatic antenna overlap with the antenna elements constituting the first transmitting / receiving antenna 21 and the antenna elements constituting the second transmitting / receiving antenna 31.

[0052] The control unit 50 of this embodiment detects a target based on the reception results of waves reflected from the target at the bistatic antenna in addition to the reception results at the transmitting / receiving antennas 21, 31.

[0053] In the radar device 1 configured as above, in order to appropriately detect a target, the control unit 50 needs to be able to distinguish between a signal received on the direct path DP and a signal received on the cross path CP.

[0054] The radar device 1 of this embodiment is configured to be able to distinguish between a received signal on a direct path DP and a received signal on a cross path CP by delaying the transmission timing from one of the transmitting / receiving antennas 21, 31 from the transmission timing of the other, as shown in, for example, FIG. 5.

[0055] Specifically, as shown in Fig. 6, the radar device 1 delays the transmission timing from one of the transmitting and receiving antennas 21, 31 from the transmission timing of the other so that the difference in baseband frequency of the transmission signals from the transmitting and receiving antennas 21, 31 is equal to or greater than the reference frequency Fs. In other words, the radar device 1 delays the transmission timing from one of the transmitting and receiving antennas 21, 31 from the transmission timing of the other so that the difference in baseband frequency of the transmission signals from the transmitting and receiving antennas 21, 31 at a predetermined timing is equal to or greater than the reference frequency Fs. The reference frequency Fs is a sampling frequency required in the direct path mode. The reference frequency Fs is defined as, for example, twice the frequency of the cutoff frequency in the direct path mode.

[0056] With this configuration, it is possible to separate the frequency band of the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. As a result, it is possible to distinguish and detect the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31.

[0057] Hereinafter, there will be described an embodiment of a method for distinguishing between a signal received on a direct path DP and a signal received on a cross path CP in the radar device 1. Note that the method described below is merely an example, and values ​​and the like may be changed as appropriate.

[0058] The radar device 1 of this embodiment is designed to detect targets up to 300 m away, which is the distance that a millimeter wave travels in 1 usec. In other words, the radar device 1 has a maximum detection range that is the distance that a millimeter wave travels in 1 usec (300 m).

[0059] For example, when a target object is present 150 m ahead, in the radar device 1, the reflected wave on the direct path DP is received by each unit 20, 30 with a timing delayed by 1 usec from the transmission timing of the transmission signal, as shown in Fig. 5. The difference in baseband frequency between the transmission signal and the reception signal at this time is set to 10 MHz in Fig. 5.

[0060] Also, when a target object is present 300 m ahead, in the radar device 1, the reflected wave on the direct path DP is received by each unit 20, 30 with a timing delayed by 2 usec from the transmission timing. The difference in baseband frequency between the transmission signal and the reception signal at this time is set to 20 MHz in FIG.

[0061] In addition, in the radar device 1, the cutoff frequency of each filter 233, 333 in the direct path mode is set to "20 MHz" corresponding to the maximum detection distance of the radar device 1. And, the sampling frequency (reference frequency Fs) of each AD converter 234, 334 in the direct path mode is set to "40 MHz", which is double the cutoff frequency according to the Nyquist theorem.

[0062] In addition, the radar device 1 is configured to delay the transmission timing of the second transmission / reception antenna 31 from the transmission timing of the first transmission / reception antenna 21 so that the difference between the baseband frequency of the transmission signal at each transmission / reception antenna 21, 31 is equal to or greater than a reference frequency Fs.

[0063] Specifically, the delay circuit 324 is configured to delay the transmission timing at the second transmitting / receiving antenna 31 from the transmission timing at the first transmitting / receiving antenna 21 by 4 usec, which corresponds to the reference frequency Fs of 40 MHz.

[0064] In the radar device 1 configured in this manner, the baseband frequency and the frequency of the IF signal in the second radar unit 30 are shifted by 40 MHz with respect to the baseband frequency and the frequency of the IF signal in the first radar unit 20.

[0065] For example, when radio waves transmitted from the first radar unit 20 and reflected by a target 150 m away are received by the second radar unit 30 (CP: RU1 → RU2), the difference in baseband frequency between the transmitted signal and the received signal is 50 MHz (= 10 MHz + 40 MHz).

[0066] Furthermore, when radio waves transmitted from the second radar unit 30 and reflected by a target 150 m away are received by the first radar unit 20 (CP: RU2 → RU1), the difference in baseband frequency between the transmitted signal and the received signal is 30 MHz (= 40 MHz - 10 MHz). In this example, since each mixer 232, 332 is capable of discriminating between positive and negative frequency components, the difference in baseband frequency can be appropriately detected.

[0067] Here, Fig. 6 is an explanatory diagram for explaining the frequency band of the IF signal obtained in the direct path mode and the frequency band of the IF signal obtained in the cross path mode. In the graph shown in Fig. 6, the vertical axis indicates the signal strength, and the horizontal axis indicates the frequency of the IF signal.

[0068] According to the radar device 1 of this embodiment, as shown in FIG. 6, the frequency band of the IF signal in the direct path mode (0 to 20 MHz) can be separated from the frequency band of the IF signal in the cross path mode (20 MHz to 40 MHz, 40 MHz to 60 MHz).

[0069] Here, in the radar device 1, the cutoff frequency of each filter 233, 333 and the sampling frequency of each AD converter 234, 334 are set according to the frequency band of the IF signal. For example, the cutoff frequency of each filter 233, 333 is set to three times (60 MHz) the reference cutoff frequency Fc, which is the cutoff frequency required in the direct path mode. The cutoff frequency may be set to a frequency that exceeds three times (120 MHz) the reference cutoff frequency Fc. Furthermore, the sampling frequency of each AD converter 234, 334 is set to three times the reference frequency Fs, which is the sampling frequency required in the direct path mode. The sampling frequency may be set to a frequency that exceeds three times the reference frequency Fs.

[0070] The above-described radar device 1 includes a sensor housing 10, a first radar unit 20, a second radar unit 30, and a control unit 50 that detects a target based on the reception results of the reflected waves reflected by the target at each of the transmitting and receiving antennas 21 and 31. The first transmitting and receiving antenna 21 and the second transmitting and receiving antenna 31 are arranged in the sensor housing 10 such that the multiple antenna elements constituting each are symmetrical with respect to a reference line BL that is equidistant from the center positions of the transmitting and receiving antennas 21 and 31. The first transmitting and receiving antenna 21 and the second transmitting and receiving antenna 31 are arranged such that the distance DL from the first position P1 to the second position P2 is not less than two times and not more than three times the antenna aperture length AL2 of each of the transmitting and receiving antennas 21 and 31. The control unit 50 generates a bistatic antenna including multiple virtual antenna elements between the transmitting and receiving antennas 21 and 31 based on the reception results of the reflected waves reflected by the target at the other antenna of the radio waves transmitted from one of the transmitting and receiving antennas 21 and 31. The control unit 50 detects the target based on the reception results of the reflected waves reflected from the target by the first transmitting / receiving antenna 21, the second transmitting / receiving antenna 31, and the bistatic antenna.

[0071] In this way, if the first radar unit 20 and the second radar unit 30 are configured to be arranged in the same sensor housing 10, the first transmitting / receiving antenna 21 and the second transmitting / receiving antenna 31 can be arranged close to each other. If the central positions of the transmitting / receiving antennas 21 and 31 are arranged at a distance of about two to three times the antenna aperture length AL2, a virtual array antenna in which the first transmitting / receiving antenna 21, the bistatic antenna, and the second transmitting / receiving antenna 31 are arranged can be realized. This virtual array antenna includes not only the bistatic antenna but also the transmitting / receiving antennas 21 and 31 provided in each unit 20 and 30, and therefore the antenna aperture length can be made larger than that of a bistatic antenna. Therefore, according to the radar device 1 of this embodiment, an antenna aperture length more than twice that of each transmitting / receiving antenna 21 and 31 provided in each unit 20 and 30 can be realized.

[0072] Moreover, according to this embodiment, the following effects can be obtained.

[0073] (1) In the configuration in which each unit 20, 30 generates a local signal individually as in the conventional technology, the influence of interference variables (phase noise, nonlinearity, time offset, etc.) of the sampled baseband signal is large. In this case, the accuracy of information (e.g., distance, angular separation, etc.) that depends on the phase of the signal detected by each unit 20, 30 is significantly deteriorated. In particular, the influence of phase noise is significantly stronger due to an incoherent oscillator than in a homodyne type device, and the accuracy of distance measurement is significantly deteriorated. In addition, the clocks of the oscillators provided in each unit 20, 30 can be synchronized to tens of nsec, but cannot be synchronized to phase noise on the order of tens of fsec. For this reason, the target detection performance is more likely to deteriorate when the antennas of each unit 20, 30 transmit and receive radio waves mutually compared to when radio waves are transmitted and received by one of the antennas of each unit 20, 30.

[0074] In contrast, in each of the units 20 and 30 of this embodiment, the local signal generated by the local signal generating section 221a of the first radar unit 20 is output to the PLL circuits 211b and 311b of the units 20 and 30, respectively.

[0075] In this way, if the units 20, 30 arranged in the same sensor housing 10 use a local signal generated by a common local signal generator 221a, it becomes easier to achieve high-precision synchronization in the units 20, 30. In this case, phase noise and the like can be received not only when radio waves are transmitted and received from one of the transmitting and receiving antennas 21, 31, but also when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31, and the target detection performance can be ensured.

[0076] (2) Each of the units 20, 30 includes a first AD converter 234 and a second AD converter 334 that convert the reception results of the reflected waves from the target into digital signals. The sampling frequency required when one of the transmitting / receiving antennas 21, 31 transmits and receives radio waves is set to a reference frequency Fs. In this case, the sampling frequency of each of the AD converters 234, 334 when the transmitting / receiving antennas 21, 31 transmit and receive radio waves mutually is set to three times the reference frequency Fs or more. This makes it possible to distinguish and detect the reception signal when the transmitting / receiving antennas 21, 31 transmit and receive radio waves mutually and the reception signal when the transmitting / receiving antennas 21, 31 transmit and receive radio waves mutually.

[0077] (3) Each unit 20, 30 is configured so that the transmission timing of radio waves from one of the transmitting / receiving antennas 21, 31 is delayed from the transmission timing of the other so that the difference in baseband frequencies of the transmission signals at each transmitting / receiving antenna 21, 31 is greater than or equal to the reference frequency Fs.

[0078] This makes it possible to separate the frequency band of a received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of a received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. Therefore, it is possible to distinguish and detect a received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from a received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. Note that the radar device 1 may be configured to delay the transmission timing of the first transmitting and receiving antenna 21 from the transmission timing of the second transmitting and receiving antenna 31.

[0079] (4) Each unit 20, 30 includes a first filter 233 and a second filter 333 that cut off frequency components outside the band used by the IF signal corresponding to the difference between the received signal and the local signal at each of the transmitting / receiving antennas 21, 31. The cutoff frequency of each filter 233, 333 when the transmitting / receiving antennas 21, 31 transmit and receive radio waves is set to be three or more times the cutoff frequency required when one of the transmitting / receiving antennas 21, 31 transmits and receives radio waves. This makes it possible to properly detect the frequency of the received signal when the transmitting / receiving antennas 21, 31 transmit and receive radio waves.

[0080] (5) Each of the units 20, 30 includes a first mixer 232 and a second mixer 332 that can distinguish between positive and negative frequency components in an IF signal. This makes it possible to appropriately detect the frequency of a received signal when radio waves are transmitted and received between the transmitting / receiving antennas 21, 31.

[0081] (6) Each of the transmitting / receiving antennas 21, 31 is arranged such that a virtual antenna element based on the reception result at one antenna overlaps with a virtual antenna element based on the reception result at the other antenna at the center of the bistatic antenna. In addition, each of the transmitting / receiving antennas 21, 31 is arranged such that the virtual antenna elements at both ends of the bistatic antenna overlap with the antenna elements constituting the first transmitting / receiving antenna 21 and the antenna elements constituting the second transmitting / receiving antenna 31. This makes it possible to realize a virtual array antenna in which the first transmitting / receiving antenna 21, the bistatic antenna, and the second transmitting / receiving antenna 31 are arranged in succession. With this virtual array antenna, it is possible to realize an antenna aperture length that is about four times that of each of the transmitting / receiving antennas 21, 31 provided in each unit 20, 30.

[0082] (Modification of the first embodiment) As in the first embodiment, when the cross path mode is configured so that radio waves corresponding to a transmission signal sent from one antenna in the direct path mode are received by the other antenna, it is possible that reflected waves reflected from a large target in the distance may be received in the cross path mode.

[0083] Therefore, as shown in FIG. 7, the control unit 50 is configured to be able to switch between the direct path mode and the cross path mode so that the direct path mode and the cross path mode can be implemented at different timings.

[0084] In such a configuration, the control unit 50 sets the cutoff frequency to three or more times the reference cutoff frequency Fc in the cross path mode. On the other hand, in the direct path mode, the control unit 50 switches the cutoff frequency of each filter 233, 333 to a frequency that does not receive a reflected wave reflected from a large target in the distance. For example, in the direct path mode, the control unit 50 switches the cutoff frequency of each filter 233, 333 to the reference cutoff frequency Fc. In addition, the control unit 50 sets the sampling frequency in the cross pass mode to three times the reference frequency Fs or more. The sampling frequency in the direct pass mode only needs to be equal to or higher than the reference frequency Fs, so the control unit 50 sets the sampling frequency to the same frequency as in the cross pass mode. The control unit 50 may be configured to switch the sampling frequency to the reference frequency Fs in the cross pass mode.

[0085] In this way, by implementing the direct path mode and the cross path mode at different times and switching the cutoff frequency of each filter 233, 333 to an appropriate frequency, it is possible to suppress reception of reflected waves from large distant targets.

[0086] Second embodiment Next, a second embodiment will be described with reference to Figures 8 and 9. In this embodiment, differences from the first embodiment will be mainly described.

[0087] The radar device 1 of this embodiment is configured to be able to distinguish between a received signal on the direct path DP and a received signal on the cross path CP by shifting the frequency of radio waves transmitted from one of the transmitting / receiving antennas 21, 31 relative to the frequency of radio waves transmitted from the other.

[0088] Such a configuration can be realized by eliminating the delay circuit 324 described in the first embodiment and instead providing a circuit for shifting the frequency of the transmission signal in at least one of the units 20, 30.

[0089] Specifically, the frequency of radio waves transmitted from one of the transmitting / receiving antennas 21, 31 is shifted relative to the frequency of radio waves transmitted from the other one so that the difference in baseband frequency of the transmission signals at each of the transmitting / receiving antennas 21, 31 is equal to or greater than a reference frequency Fs. The reference frequency Fs is a sampling frequency required in the direct path mode.

[0090] With this configuration, it is possible to separate the frequency band of the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. As a result, it is possible to distinguish and detect the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31.

[0091] Hereinafter, a description will be given of an example of a method for distinguishing between a signal received on a direct path DP and a signal received on a cross path CP in the radar device 1. Note that the performance and various settings of the radar device 1 are assumed to be the same as those in the example described in the first embodiment.

[0092] 8, the radar device 1 transmits transmission signals at the same timing from each of the transmitting and receiving antennas 21 and 31. At this time, the radar device 1 shifts the frequency of the transmission signal of the second transmitting and receiving antenna 31 relative to the frequency of the transmission signal of the first transmitting and receiving antenna 21 so that the difference between the baseband frequency of the transmission signal at each of the transmitting and receiving antennas 21 and 31 becomes a reference frequency Fs.

[0093] In the radar device 1 configured in this manner, the baseband frequency and the frequency of the IF signal in the second radar unit 30 are shifted relative to the baseband frequency and the frequency of the IF signal in the first radar unit 20 by the reference frequency Fs (40 MHz).

[0094] For example, when radio waves transmitted from the first radar unit 20 and reflected by a target 150 m away are received by the second radar unit 30 (CP: RU1 → RU2), the difference in baseband frequency between the transmitted signal and the received signal is 50 MHz (= 10 MHz + 40 MHz).

[0095] In addition, when the first radar unit 20 receives radio waves transmitted from the second radar unit 30 and reflected by a target 150 m away (CP: RU2 → RU1), the difference in baseband frequency between the transmitted signal and the received signal is 30 MHz (= 40 MHz - 10 MHz).

[0096] Here, Fig. 9 is an explanatory diagram for explaining the frequency band of the IF signal obtained in the direct path mode and the frequency band of the IF signal obtained in the cross path mode. In the graph shown in Fig. 9, the vertical axis indicates the signal strength, and the horizontal axis indicates the frequency of the IF signal.

[0097] According to the radar device 1 of this embodiment, as shown in FIG. 9, the frequency band of the IF signal in the direct path mode (0 to 20 MHz) can be separated from the frequency band of the IF signal in the cross path mode (20 MHz to 40 MHz, 40 MHz to 60 MHz).

[0098] The rest is the same as in the first embodiment. The radar device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0099] Moreover, the radar device 1 of this embodiment has the following features.

[0100] (1) Each unit 20, 30 shifts the frequency of one transmission signal from each transmitting / receiving antenna 21 relative to the frequency of the other transmission signal so that the difference in baseband frequencies of the transmission signals at each transmitting / receiving antenna 21, 31 is equal to or greater than the reference frequency Fs.

[0101] This makes it possible to separate the frequency band of a received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of a received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. Therefore, it is possible to distinguish and detect a received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from a received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. Note that the radar device 1 may be configured to shift the frequency of the transmission signal of the first transmitting and receiving antenna 21 with respect to the frequency of the transmission signal of the second transmitting and receiving antenna 31.

[0102] Third embodiment Next, a third embodiment will be described with reference to Figures 10 and 11. In this embodiment, differences from the second embodiment will be mainly described.

[0103] As in the second embodiment, when the cross path mode is configured so that radio waves corresponding to a transmission signal sent from one antenna in the direct path mode are received by the other antenna, a reflected wave reflected from a large target in the distance may be received in the cross path mode.

[0104] In contrast, the radar device 1 of this embodiment sets the amount of frequency shift of the radio waves transmitted from one of the transmitting / receiving antennas 21, 31 relative to the frequency of the radio waves transmitted from the other antenna, so as to avoid receiving reflected waves reflected from large targets in the distance in cross-path mode.

[0105] Specifically, the transmission frequency of one of the transmitting / receiving antennas 21, 31 is shifted relative to the transmission frequency of the other so that the difference in baseband frequency of the transmission signals at each of the transmitting / receiving antennas 21, 31 is at least twice the detection distance frequency corresponding to the maximum detection distance of the radar device 1. The maximum detection distance is the maximum distance to a target object in the radar device 1. The detection distance frequency is the fluctuation width of the frequency that changes during the period until the travel distance of the radio wave reaches the maximum detection distance.

[0106] With this configuration, it is possible to greatly separate the frequency band of the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31. As a result, it is possible to distinguish and detect the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the received signal when radio waves are transmitted and received between the transmitting and receiving antennas 21, 31.

[0107] Hereinafter, a description will be given of an example of a method for distinguishing between a signal received on a direct path DP and a signal received on a cross path CP in the radar device 1. Note that the performance and various settings of the radar device 1 are assumed to be the same as those in the example described in the first embodiment.

[0108] 10, the radar device 1 transmits transmission signals at the same timing from each of the transmitting and receiving antennas 21 and 31. At this time, the radar device 1 shifts the frequency of the transmission signal of the second transmitting and receiving antenna 31 relative to the frequency of the transmission signal of the first transmitting and receiving antenna 21 so that the difference between the baseband frequency of the transmission signal at each of the transmitting and receiving antennas 21 and 31 is three times the detection distance frequency.

[0109] In the radar device 1 configured in this manner, the baseband frequency and the frequency of the IF signal in the second radar unit 30 are shifted from the baseband frequency and the frequency of the IF signal in the first radar unit 20 by three times the detection distance frequency (60 MHz).

[0110] For example, when radio waves transmitted from the first radar unit 20 and reflected by a target 150 m away are received by the second radar unit 30 (CP: RU1 → RU2), the difference in baseband frequency between the transmitted signal and the received signal is 70 MHz (= 10 MHz + 60 MHz).

[0111] In addition, when the first radar unit 20 receives radio waves transmitted from the second radar unit 30 and reflected by a target 150 m away (CP: RU2 → RU1), the difference in baseband frequency between the transmitted signal and the received signal is 50 MHz (= 60 MHz - 10 MHz).

[0112] Here, Fig. 11 is an explanatory diagram for explaining the frequency band of the IF signal obtained in the direct path mode and the frequency band of the IF signal obtained in the cross path mode. In the graph shown in Fig. 11, the vertical axis indicates the signal strength, and the horizontal axis indicates the frequency of the IF signal.

[0113] According to the radar device 1 of this embodiment, as shown in FIG. 11, the frequency band of the IF signal in the direct path mode (0 to 20 MHz) can be separated from the frequency band of the IF signal in the cross path mode (40 MHz to 60 MHz, 60 MHz to 80 MHz).

[0114] In this embodiment, the frequency band (20 MHz to 40 MHz) between the frequency band of the IF signal in the direct path mode and the frequency band of the IF signal in the cross path mode is secured to allow waves reflected from large distant targets.

[0115] Here, in the radar device 1, the cutoff frequency of each filter 233, 333 and the sampling frequency of each AD converter 234, 334 are set according to the frequency band of the IF signal. For example, the cutoff frequency of each filter 233, 333 is set to four times (80 MHz) the reference cutoff frequency Fc, which is the cutoff frequency required in the direct path mode. The cutoff frequency may be set to a frequency that exceeds four times the reference cutoff frequency Fc. Furthermore, the sampling frequency of each AD converter 234, 334 is set to four times (160 MHz) the reference frequency Fs, which is the sampling frequency required in the direct path mode. The sampling frequency may be set to a frequency that exceeds four times the reference frequency Fs.

[0116] The rest is the same as in the first embodiment. The radar device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0117] Moreover, the radar device 1 of this embodiment has the following features.

[0118] (1) Each unit 20, 30 shifts the frequency of one transmission signal from each transmitting / receiving antenna 21 relative to the frequency of the other transmission signal so that the difference in baseband frequencies of the transmission signals at each transmitting / receiving antenna 21, 31 is three times the detection distance frequency.

[0119] This makes it easier to separate the frequency band of the received signal when radio waves are transmitted and received by one of the transmitting and receiving antennas 21, 31 from the frequency band of the received signal when radio waves are transmitted and received by each of the transmitting and receiving antennas 21, 31. Therefore, it is possible to detect the received signal received in the direct path mode and the received signal received in the cross path mode separately. For example, it is possible to prevent the reflected wave reflected by a large target in the distance in the direct path mode from being received in the cross path mode. In particular, in the configuration of this example, the frequency of the radio waves transmitted from each of the transmitting and receiving antennas 21, 31 is merely shifted, and switching of the cutoff frequency is not required. Note that the radar device 1 may shift the frequency of the transmission signal of the first transmitting and receiving antenna 21 relative to the frequency of the transmission signal of the second transmitting and receiving antenna 31. In addition, it is only necessary that the baseband frequency and the frequency of the IF signal of one of the units 20, 30 are shifted by more than twice the detection distance frequency relative to the frequency of the baseband frequency and the frequency of the IF signal of the other unit.

[0120] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0121] In the above embodiment, a specific antenna configuration of the radar device 1 is exemplified, but the antenna configuration of the radar device 1 is not limited to the above, and may be an antenna configuration different from the above. For example, the transmitting / receiving antennas 21, 31 are configured as MIMO antennas including virtual antenna elements, but the present invention is not limited to this, and may be configured, for example, only with actual antenna elements.

[0122] As in the above embodiment, the antenna configuration of the radar device 1 is preferably configured such that the virtual array antenna is configured such that the first transmitting / receiving antenna 21, the bistatic antenna, and the second transmitting / receiving antenna 31 are continuously arranged, but is not limited to this. The antenna configuration of the radar device 1 may be configured such that a virtual array antenna is generated that includes a portion that is discontinuous.

[0123] In the above embodiment, a specific configuration of each unit 20, 30 is exemplified, but the configuration of each unit 20, 30 is not limited to the above. For example, the radar device 1 in the above embodiment is configured such that a local signal generated by the first local oscillator 221 provided in the first radar unit 20 is provided to the second local oscillator 321, but is not limited to this. The radar device 1 may be configured such that a local signal generated by the second local oscillator 321 provided in the second radar unit 30 is provided to the first local oscillator 221. Also, a local signal generated by an oscillator provided separately from each unit 20, 30 may be provided to each local oscillator 221, 321.

[0124] In the above-described embodiment, a specific example of a method for distinguishing between a received signal on the direct path DP and a received signal on the cross path CP in the radar device 1 is given, but the method is not limited to the above-described method and may be different from the above-described method.

[0125] In the above embodiment, an example has been described in which the radar device 1 of the present disclosure is applied to a target detection device that is mounted on a vehicle and detects various targets present around the vehicle, but the application of the radar device 1 is not limited to this. The radar device 1 can also be applied to, for example, moving objects other than vehicles and stationary devices.

[0126] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0127] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0128] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc. [Explanation of symbols]

[0129] 1. Radar equipment 20. 1st Radar Unit 21 First transmitting / receiving antenna 30 2nd Radar Unit 31 Second transmitting / receiving antenna 50 Control section

Claims

1. A radar device that detects targets using radio waves, A sensor housing (10); A first radar unit (20) including a first transmitting / receiving antenna (21) for transmitting and receiving radio waves; a second radar unit (30) including a second transmitting / receiving antenna (31) for transmitting and receiving radio waves; a control unit (50) that detects the target based on reception results of a reflected wave reflected from the target at each of the first transmitting / receiving antenna and the second transmitting / receiving antenna, When a virtual line that is equidistant from a first position (P1) that is a center position of the first transmission / reception antenna in an arrangement direction of the first transmission / reception antenna and the second transmission / reception antenna, and a second position (P2) that is a center position of the second transmission / reception antenna in the arrangement direction is defined as a reference line (BL), the first transmitting / receiving antenna and the second transmitting / receiving antenna are arranged on the sensor housing such that a plurality of antenna elements constituting each antenna are linearly symmetrical with respect to the reference line, and are arranged such that a distance (DL) from the first position to the second position is not less than two times and not more than three times an antenna aperture length (PL2) of the first transmitting / receiving antenna and the second transmitting / receiving antenna, The control unit generates a bistatic antenna including a plurality of virtual antenna elements between the first transmission / reception antenna and the second transmission / reception antenna based on a reception result at the other antenna of a reflected wave formed when a radio wave is transmitted from one of the first transmission / reception antenna and the second transmission / reception antenna and reflected by the target, and detects the target based on a reception result at the first transmission / reception antenna, the second transmission / reception antenna, and the bistatic antenna of the reflected wave formed by the target.

2. The first radar unit and the second radar unit each include an AD conversion unit (234, 334) that converts a reception result of a reflected wave reflected by the target into a digital signal, 2. The radar device according to claim 1, wherein, when a sampling frequency required when transmitting and receiving radio waves from one of the first transmitting and receiving antenna and the second transmitting and receiving antenna is defined as a reference frequency (Fs), the AD conversion unit sets a sampling frequency when transmitting and receiving radio waves between the first transmitting and receiving antenna and the second transmitting and receiving antenna to be three or more times the reference frequency.

3. 3. The radar device according to claim 2, wherein the first radar unit and the second radar unit are configured so that a transmission timing of radio waves from one of the first transmitting / receiving antenna and the second transmitting / receiving antenna is delayed from a transmission timing of the other such that a difference between a baseband frequency of a transmission signal at the first transmitting / receiving antenna and a baseband frequency of a transmission signal at the second transmitting / receiving antenna is equal to or greater than the reference frequency.

4. 3. The radar device according to claim 2, wherein the first radar unit and the second radar unit are configured to shift the frequency of radio waves transmitted from one of the first transmitting / receiving antenna and the second transmitting / receiving antenna relative to the frequency of radio waves transmitted from the other antenna such that a difference between a baseband frequency of a transmission signal at the first transmitting / receiving antenna and a baseband frequency of a transmission signal at the second transmitting / receiving antenna is equal to or greater than the reference frequency.

5. the first radar unit and the second radar unit each include a low-pass filter (233, 333) configured to cut frequency components outside the band of an intermediate frequency signal corresponding to a difference between a received signal at the first transmitting / receiving antenna and a local signal at the second transmitting / receiving antenna, 5. The radar device according to claim 3, wherein when a cutoff frequency required when transmitting and receiving radio waves from one of the first transmitting and receiving antenna and the second transmitting and receiving antenna is defined as a reference cutoff frequency (Fc), the cutoff frequency of the low-pass filter when transmitting and receiving radio waves between the first transmitting and receiving antenna and the second transmitting and receiving antenna is set to be three or more times the reference cutoff frequency.

6. 6. The radar device according to claim 5, wherein the first radar unit and the second radar unit each include a mixer (232, 332) capable of distinguishing between positive and negative frequency components in the intermediate frequency signal.

7. 3. The radar device according to claim 1, wherein the first and second transmitting / receiving antennas are arranged such that, at a central portion of the bistatic antenna, the virtual antenna element based on a reception result of a wave reflected by the target at one antenna and the virtual antenna element based on a reception result of a wave reflected by the target at the other antenna overlap with each other, and the virtual antenna elements at both ends of the bistatic antenna overlap with an antenna element constituting the first transmitting / receiving antenna and an antenna element constituting the second transmitting / receiving antenna.

8. the control unit executes, at different timings, a direct path mode in which radio waves are transmitted and received by one of the first transmission / reception antenna and the second transmission / reception antenna, and a cross path mode in which radio waves are transmitted and received by both the first transmission / reception antenna and the second transmission / reception antenna, 6. The radar device according to claim 5, wherein a cutoff frequency of the low-pass filter is set to three or more times the reference cutoff frequency in the cross-pass mode, and the cutoff frequency of the low-pass filter is set to the reference cutoff frequency when the mode is switched from the cross-pass mode to the direct mode.

9. When the maximum value of the distance to the target object is defined as the maximum detection distance, and the frequency corresponding to the maximum detection distance is defined as the detection distance frequency, 3. The radar device according to claim 2, wherein the first radar unit and the second radar unit are configured to shift the frequency of radio waves transmitted from one of the first transmitting / receiving antenna and the second transmitting / receiving antenna relative to the frequency of radio waves transmitted from the other such that a difference between a baseband frequency of a transmission signal at the first transmitting / receiving antenna and a baseband frequency of a transmission signal at the second transmitting / receiving antenna is equal to or greater than twice the detection distance frequency.

Images