Radar apparatus

Abstract

To achieve a desired directivity pattern by suppressing generation of an unnecessary grating lobe even in the case of a sub-array antenna configuration.SOLUTION: In the radar device, a first interval between two adjacent transmission antennas among the plurality of transmission antennas is one wavelength or more in the first direction, an interval between two adjacent reception antennas among the plurality of reception antennas is one wavelength or more in the first direction and is narrower than the first interval between the transmission antennas, and a second interval between two adjacent transmission antennas among the plurality of transmission antennas is 0.5 wavelength or more and 0.75 wavelength or less in the second direction. An absolute value of a difference between the first interval between the two adjacent transmission antennas and the interval between the two adjacent reception antennas includes an interval of 0.5 wavelength or more and 0.75 wavelength or less in the first direction, a size of each of the plurality of transmission antennas in the short-side direction is 0.5 wavelength or less, and a size of each of the plurality of reception antennas in the short-side direction is 0.5 wavelength or less.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a radar device. [Background technology]

[0002] In recent years, radar devices using short-wavelength radar transmission signals, including microwaves and millimeter waves, which can provide high resolution, have been studied. Furthermore, to improve outdoor safety, there is a demand for the development of radar devices that can detect objects (targets) including pedestrians in addition to vehicles over a wide angle range.

[0003] For example, a pulse radar device that repeatedly emits pulse waves is known as a radar device. The received signal of a wide-angle pulse radar that detects vehicles / pedestrians over a wide angle range is a mixture of multiple reflected waves from targets (e.g., vehicles) located in close range and targets (e.g., pedestrians) located in long range. For this reason, (1) the radar transmitter must be configured to transmit pulse waves or pulse-modulated waves with autocorrelation characteristics that result in low range side lobes (hereinafter referred to as low range side lobe characteristics), and (2) the radar receiver must be configured to have a wide reception dynamic range.

[0004] The wide-angle radar device can be configured in the following two ways.

[0005] The first is a configuration in which pulsed or modulated waves are transmitted using a narrow-angle (a few degrees wide) directional beam, scanned mechanically or electronically, and the reflected waves are received using a narrow-angle directional beam. This configuration requires multiple scans to achieve high resolution, which reduces tracking ability for fast-moving targets.

[0006] The second configuration uses a method called Direction of Arrival (DOA) estimation, which receives reflected waves using an array antenna composed of multiple antennas (antenna elements) and estimates the angle of arrival of the reflected waves using a signal processing algorithm based on the reception phase difference relative to the antenna spacing. With this configuration, even if the scanning interval of the transmission beam at the radar transmitter is thinned, the arrival angle can be estimated at the radar receiver, thereby shortening the scanning time and improving tracking performance compared to the first configuration. For example, methods for estimating the direction of arrival include Fourier transform based on matrix operations, Capon's method and LP (Linear Prediction) method based on inverse matrix operations, and MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) based on eigenvalue operations.

[0007] Furthermore, a radar device has been proposed that includes multiple antennas (array antennas) in the radar transmitter as well as the radar receiver, and performs beam scanning by signal processing using the transmitting and receiving array antennas (sometimes called MIMO radar) (see, for example, Non-Patent Document 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2011-526370 [Non-patent literature]

[0009] [Non-Patent Document 1] Budisin, SZ, "New complementary pairs of sequences," Electron. Lett., 1990, 26, (13), pp.881-883 [Non-patent document 2] Jian Li, Stoica, Petre, "MIMO Radar with Colocated Antennas," Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 Summary of the Invention [Problem to be solved by the invention]

[0010] In order to increase the directional gain of an array antenna, a sub-array antenna may be used in which each of the antenna elements (hereinafter referred to as an array element) constituting the array antenna is further composed of a plurality of antenna elements.

[0011] It is difficult to arrange the element spacing of an array antenna at a spacing narrower than the size of the array elements. However, when using a sub-array antenna configuration, the size of the array elements increases, so the spacing between the sub-array antennas must be increased, which can cause grating lobes to appear in the directional pattern of the array antenna.

[0012] One aspect of the present disclosure provides a radar device that can suppress the occurrence of unnecessary grating lobes and achieve a desired directivity pattern even in the case of a sub-array antenna configuration. [Means for solving the problem]

[0013] A radar device according to one aspect of the present disclosure includes a transmitting array antenna, a receiving array antenna, a radar transmitter that transmits radar signals using the transmitting array antenna, and a radar receiver that receives, using the receiving array antenna, reflected wave signals of the radar signals reflected by a target, wherein the transmitting array antenna includes a plurality of transmitting antennas, the receiving array antenna includes a plurality of receiving antennas, the plurality of transmitting antennas being arranged at different positions in a first direction, and the plurality of receiving antennas being arranged at different positions in the first direction. The spacing between two adjacent transmitting antennas among the plurality of transmitting antennas is one wavelength or more in the first direction, the spacing between two adjacent receiving antennas among the plurality of receiving antennas is one wavelength or more in the first direction, the absolute value of the difference between the spacing between the two adjacent transmitting antennas and the spacing between the two adjacent receiving antennas is 0.5 wavelengths or more and 0.75 wavelengths or less in the first direction, and at least one of the plurality of transmitting antennas and the plurality of receiving antennas includes a plurality of antenna elements arranged in the first direction. A radar device according to another embodiment of the present disclosure includes a first array antenna, a second array antenna, a radar transmitter that transmits radar signals using one of the first array antenna and the second array antenna, and a radar receiver that receives, using the other of the first array antenna and the second array antenna, reflected wave signals of the radar signals reflected by a target, wherein the first array antenna includes a plurality of first antennas, each of the plurality of first antennas being arranged at a different position in a first direction, and the second array antenna includes a plurality of second antennas, each of the plurality of second antennas being arranged at a different position in a first direction. each of the plurality of first antennas is arranged at a different position in the first direction, the interval between two adjacent first antennas among the plurality of first antennas is one wavelength or more in the first direction, the interval between two adjacent second antennas among the plurality of second antennas is one wavelength or more in the first direction, and an absolute value of a difference between the interval between the two adjacent first antennas and the interval between the two adjacent second antennas is 0.5 wavelength or more and 0.75 wavelength or less in the first direction, and at least one of the plurality of first antennas and the plurality of second antennas includes a plurality of antenna elements arranged in the first direction.

[0014] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0015] According to one aspect of the present disclosure, even in the case of a sub-array antenna configuration, it is possible to suppress the occurrence of unnecessary grating lobes and achieve a desired directivity pattern.

[0016] Further advantages and benefits of certain aspects of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0017] [Figure 1A] A diagram showing an example of the configuration of a subarray element. [Figure 1B] A diagram showing an example of the configuration of an array antenna made up of subarray elements. [Figure 2] FIG. 1 is a block diagram illustrating a configuration of a radar device according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a diagram illustrating an example of a radar transmission signal according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a block diagram illustrating another configuration of the radar transmission signal generator according to the embodiment of the present disclosure. [Figure 5] FIG. 1 is a diagram illustrating an example of a transmission timing and a measurement range of a radar transmission signal according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a diagram showing antenna arrangements of a transmitting array, a receiving array, and a virtual receiving array according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a diagram illustrating a directivity pattern according to an embodiment of the present disclosure. [Figure 8] FIG. 10 is a diagram showing antenna arrangements of a transmitting array, a receiving array, and a virtual receiving array according to a first variation of an embodiment of the present disclosure. [Figure 9A] FIG. 10 is a diagram showing a horizontal directivity pattern according to Variation 1 of the embodiment of the present disclosure. [Figure 9B] FIG. 10 is a diagram showing a vertical directivity pattern according to Variation 1 of the embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram showing antenna arrangements of a transmitting array, a receiving array, and a virtual receiving array according to a second variation of an embodiment of the present disclosure. [Figure 11A]FIG. 10 is a diagram showing a horizontal directivity pattern according to Variation 2 of the embodiment of the present disclosure. [Figure 11B] FIG. 10 is a diagram showing a vertical directivity pattern according to Variation 2 of the embodiment of the present disclosure. [Figure 12] FIG. 10 is a diagram showing antenna arrangements of a transmitting array, a receiving array, and a virtual receiving array according to a third variation of an embodiment of the present disclosure. [Figure 13A] FIG. 10 is a diagram showing a horizontal directivity pattern according to Variation 3 of the embodiment of the present disclosure. [Figure 13B] FIG. 10 is a diagram showing a vertical directivity pattern according to Variation 3 of the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] [Background to one aspect of the present disclosure] Figure 1A shows an example of an antenna element with a subarray configuration (hereinafter, sometimes referred to as a subarray element). The subarray element shown in Figure 1A is composed of four antenna elements in a 2x2 arrangement. In the example shown in Figure 1A, the size of the subarray element is 0.8 wavelengths in both the horizontal and vertical directions.

[0019] Figure 1B shows an example of an array antenna configured by arranging four subarray elements shown in Figure 1A in series. As shown in Figure 1B, the size of each subarray element is 0.8 wavelengths (see Figure 1A), so the spacing between the subarray elements must be at least one wavelength.

[0020] For example, the array element spacing (desired element spacing) required to prevent grating lobes from occurring within ±90° of the main lobe is 0.5 wavelengths. In the array antenna shown in Figure 1B, the element spacing of the subarray elements is approximately one wavelength or more, making it difficult to set the desired element spacing, and grating lobes will occur within ±90° of the main lobe.

[0021] As described above, when the size of the subarray elements is 0.5 wavelengths or more, it may be difficult to set the element spacing of the array antenna to 0.5 wavelengths. As a result, unwanted grating lobes occur within ±90° of the main lobe, which causes false images during angle measurement and leads to erroneous detection.

[0022] Here, Patent Document 1 discloses an array antenna configuration using sub-array elements with a width d of approximately 1 wavelength. In Patent Document 1, the element spacing between transmitting antennas Tx0 and Tx1 is 6 wavelengths, and the element spacing between receiving antennas RX0, RX1, RX2, and RX3 is 1.5 wavelengths ±(λ / 8) (λ represents 1 wavelength). Furthermore, Patent Document 1 also includes a configuration in which radar transmission signals are transmitted by switching between transmitting antennas Tx0 and Tx1 in a time-division manner, and received signals are acquired by receiving antennas RX0, RX1, RX2, and RX3 in response to the radar transmission signals transmitted from each transmitting antenna Tx0 and Tx1.

[0023] With this configuration, the phase change caused by the change in the position of the transmitting antenna is superimposed on the received signal acquired by the receiving array antenna, which has the effect of virtually increasing the aperture length of the receiving antenna. Hereinafter, a virtual receiving array antenna whose effective aperture length is increased by the arrangement of antenna elements in the transmitting and receiving array antennas will be referred to as a "virtual receiving array."

[0024] However, in Patent Document 1, the element spacing of the receiving array antenna is 1.5 wavelengths±λ / 8, which results in grating lobes occurring in directions shifted by about 40° from the main beam direction.

[0025] According to one aspect of the present disclosure, even when array elements in a subarray configuration are used, the occurrence of unwanted grating lobes is suppressed and a desired directivity pattern is achieved.

[0026] Hereinafter, an embodiment according to one aspect of the present disclosure will be described in detail with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and redundant descriptions thereof will be omitted.

[0027] [Radar device configuration] FIG. 2 is a block diagram showing the configuration of the radar device 10 according to this embodiment.

[0028] The radar device 10 includes a radar transmitter 100, a radar receiver 200, and a reference signal generator 300.

[0029] The radar transmitter 100 generates a high-frequency radar signal (radar transmission signal) based on the reference signal received from the reference signal generator 300. The radar transmitter 100 then transmits the radar transmission signal at a predetermined transmission period using a transmission array antenna configured by multiple transmission antennas 106-1 to 106-Nt.

[0030] The radar receiver 200 receives reflected wave signals, which are radar transmission signals reflected by a target (not shown), using a receiving array antenna consisting of multiple receiving antennas 202-1 to 202-Na. The radar receiver 200 performs signal processing on the reflected wave signals received by each antenna 202 using a reference signal received from the reference signal generator 300, and performs detection of the presence or absence of a target, estimation of the direction, etc. The target is an object to be detected by the radar device 10, and includes, for example, a vehicle or a person.

[0031] The reference signal generating unit 300 is connected to both the radar transmitting unit 100 and the radar receiving unit 200. The reference signal generating unit 300 supplies a reference signal as a reference signal to both the radar transmitting unit 100 and the radar receiving unit 200, thereby synchronizing the processing of the radar transmitting unit 100 and the radar receiving unit 200.

[0032] [Configuration of radar transmitter 100] The radar transmitter 100 includes radar transmission signal generators 101-1 to 101-Nt, radio transmission units 105-1 to 105-Nt, and transmission antennas 106-1 to 106-Nt. That is, the radar transmitter 100 includes Nt transmission antennas 106, and each transmission antenna 106 is connected to an individual radar transmission signal generator 101 and radio transmission unit 105.

[0033] The radar transmission signal generator 101 generates a timing clock by multiplying the reference signal received from the reference signal generator 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. The radar transmission signal generator 101 then repeatedly outputs the radar transmission signal at a predetermined radar transmission period (Tr). The radar transmission signal is z (k, M)=I z (k, M)+jQ z (k, M), where z represents a number corresponding to each transmitting antenna 106, z=1,...,Nt, j represents the imaginary unit, k represents discrete time, and M represents the ordinal number of the radar transmission period.

[0034] Each radar transmission signal generator 101 includes a code generator 102, a modulator 103, and an LPF (Low Pass Filter) 104. Below, we will explain each component of the radar transmission signal generator 101-z corresponding to the zth (z=1, ..., Nt) transmitting antenna 106.

[0035] Specifically, the code generation unit 102 generates a code a(z) of a code sequence having a code length L for each radar transmission period Tr. n (n=1, ..., L) (pulse code) is generated. The code a(z) generated in each code generation unit 102-1 to 102-Nt is n Codes that are lowly correlated or uncorrelated with each other are used for (z=1, . . . , Nt). Examples of code sequences include Walsh-Hadamard codes, M-sequence codes, and Gold codes.

[0036] The modulation unit 103 modulates the code a(z) received from the code generation unit 102. nThe LPF 104 performs pulse modulation (amplitude modulation, ASK (Amplitude Shift Keying), pulse shift keying) or phase modulation (Phase Shift Keying) on ​​the signal, and outputs the modulated signal to the LPF 104.

[0037] The LPF 104 outputs signal components below a predetermined band limit, out of the modulated signal received from the modulation unit 103, to the transmission radio unit 105 as a baseband radar transmission signal.

[0038] The zth (z=1, ..., Nt) radio transmission unit 105 performs frequency conversion on the baseband radar transmission signal output from the zth radar transmission signal generation unit 101 to generate a radar transmission signal in the carrier frequency (Radio Frequency: RF) band, amplifies the signal to a predetermined transmission power P [dB] using a transmission amplifier, and outputs the amplified signal to the zth transmission antenna 106.

[0039] The zth (z=1, . . . , Nt) transmitting antenna 106 radiates the radar transmission signal output from the zth radio transmission unit 105 into space.

[0040] FIG. 3 shows radar transmission signals transmitted from the Nt transmitting antennas 106 of the radar transmitter 100. A pulse code sequence with a code length L is included in the code transmission interval Tw. In each radar transmission period Tr, the pulse code sequence is transmitted during the code transmission interval Tw, and the remaining interval (Tr-Tw) is a no-signal interval. One pulse code (a(z) n ), pulse modulation using No samples is performed, so that each code transmission interval Tw contains a signal of Nr (=No×L) samples. That is, the sampling rate in the modulation unit 103 is (No×L) / Tw. Also, it is assumed that a no-signal interval (Tr-Tw) contains Nu samples.

[0041] The radar transmitter 100 may include a radar transmission signal generator 101a shown in Fig. 4 instead of the radar transmission signal generator 101. The radar transmission signal generator 101a does not include the code generator 102, modulator 103, and LPF 104 shown in Fig. 2, but instead includes a code storage unit 111 and a DA converter 112. The code storage unit 111 stores in advance the code sequence generated by the code generator 102 (Fig. 2) and cyclically reads out the stored code sequences one by one. The DA converter 112 converts the code sequence (digital signal) output from the code storage unit 111 into an analog signal.

[0042] [Configuration of radar receiver 200] 2, the radar receiving unit 200 includes Na receiving antennas 202, which form an array antenna. The radar receiving unit 200 also includes Na antenna system processing units 201-1 to 201-Na and a direction estimating unit 214.

[0043] Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected by a target (object), and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0044] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 207 .

[0045] Radio reception unit 203 has amplifier 204, frequency converter 205, and quadrature detector 206. Radio reception unit 203 generates a timing clock by multiplying the reference signal received from reference signal generator 300 by a predetermined number, and operates based on the generated timing clock. Specifically, amplifier 204 amplifies the received signal received from receiving antenna 202 to a predetermined level, frequency converter 205 frequency-converts the received signal in the high frequency band to the baseband, and quadrature detector 206 converts the received signal in the baseband into a received signal in the baseband including an I signal and a Q signal.

[0046] Signal processing section 207 has AD conversion sections 208 and 209 and separation sections 210-1 to 210-Nt.

[0047] The I signal is input to AD conversion unit 208 from quadrature detector 206, and the Q signal is input to AD conversion unit 209 from quadrature detector 206. AD conversion unit 208 performs discrete time sampling on the baseband signal including the I signal to convert the I signal into digital data. AD conversion unit 209 performs discrete time sampling on the baseband signal including the Q signal to convert the Q signal into digital data.

[0048] Here, the AD converters 208 and 209 perform sampling by taking Ns discrete samples per time Tp (=Tw / L) of one subpulse in the radar transmission signal, i.e., the number of oversamples per subpulse is Ns.

[0049] In the following description, the baseband received signal at discrete time k of the Mth radar transmission cycle Tr[M] as the output of the AD conversion units 208 and 209 is expressed as a complex signal x(k,M)=Ir(k,M)+jQr(k,M) using the I signal Ir(k,M) and the Q signal Qr(k,M). Here, the discrete time k is defined as the start timing of the radar transmission cycle (Tr) (k=1), and the signal processing unit 207 operates cyclically up to k=(Nr+Nu)Ns / No, which is the sampling point before the radar transmission cycle Tr ends. That is, k=1,...,(Nr+Nu)Ns / No. Here, j is the imaginary unit.

[0050] The signal processing unit 207 includes Nt separators 210, the number of which is equal to the number of systems corresponding to the number of transmitting antennas 106. Each separator 210 has a correlation calculation unit 211, an addition unit 212, and a Doppler frequency analysis unit 213. The configuration of the zth (z=1, ..., Nt) separator 210 will be described below.

[0051] The correlation calculation unit 211 calculates, for each radar transmission period Tr, discrete sample values ​​x(k,M) including discrete sample values ​​Ir(k,M) and Qr(k,M) received from the AD conversion units 208 and 209, and a pulse code a(z) of code length L transmitted by the radar transmission unit 100. n (where z=1, . . . , Nt, n=1, . . . , L). For example, the correlation calculation unit 211 calculates the correlation between the discrete sample value x(k, M) and the pulse code a(z) n For example, the correlation calculation value AC of the sliding correlation calculation at discrete time k in the M-th radar transmission period Tr[M] is (z) (k, M) is calculated based on the following formula:

number

[0052] In the above formula, the asterisk (*) represents the complex conjugate operator.

[0053] The correlation calculation unit 211 performs correlation calculations over periods of k=1, . . . , (Nr+Nu)Ns / No, for example, in accordance with equation (1).

[0054] Note that the correlation calculation unit 211 is not limited to performing correlation calculations for k=1,...,(Nr+Nu)Ns / No, and may limit the measurement range (i.e., the range of k) depending on the range of targets to be measured by the radar device 10. This enables the radar device 10 to reduce the amount of calculation processing by the correlation calculation unit 211. For example, the correlation calculation unit 211 may limit the measurement range to k=Ns(L+1),...,(Nr+Nu)Ns / No-NsL. In this case, as shown in FIG. 5, the radar device 10 does not perform measurements in the time period corresponding to the code transmission period Tw.

[0055] As a result, even if the radar transmission signal directly penetrates the radar receiving unit 200, the radar device 10 does not perform processing by the correlation calculation unit 211 during the period in which the radar transmission signal penetrates (at least a period shorter than τ1), thereby enabling measurement without the influence of the penetration. Furthermore, when limiting the measurement range (the range of k), similar processing that limits the measurement range (the range of k) can be applied to the processing of the adder 212, Doppler frequency analysis unit 213, and direction estimation unit 214 described below. This reduces the processing amount in each component and reduces power consumption in the radar receiving unit 200.

[0056] The adder 212 receives the correlation calculation value AC (z) Using (k, M), the correlation calculation value AC is calculated over a period (Tr × Np) of a predetermined number (Np) of radar transmission cycles Tr. (z) (k, M) are summed (coherent integrated). The summation (coherent integration) process of Np sums over a period (Tr × Np) is expressed by the following equation.

number

[0057] Here, CI (z) (k, m) represents the sum of correlation calculation values ​​(hereinafter also referred to as correlation sum), Np is an integer value of 1 or more, and m is an integer of 1 or more that indicates the ordinal number of the number of additions when the number of additions Np in adder 212 is taken as one unit. Also, z=1,...,Nt.

[0058] The adder 212 performs addition Np times, with the output of the correlation calculator 211 obtained in units of the radar transmission period Tr as one unit. (z) (k, Np(m-1)+1)~AC (z) The correlation value CI obtained by adding the discrete time k (k, Np×m) together as a unit is (z)(k, m) is calculated for each discrete time k. As a result, the adder 212 can improve the SNR of the reflected wave signal in a range where the reflected wave signal from the target has a high correlation due to the effect of adding the correlation calculation values ​​Np times. Therefore, the measurement performance for estimating the target arrival distance can be improved.

[0059] To obtain an ideal addition gain, it is necessary to set a condition that the phase components of the correlation calculation values ​​are aligned within a certain range during the addition interval of the number of additions Np of the correlation calculation values. In other words, it is preferable to set the number of additions Np based on the expected maximum moving speed of the target to be measured. This is because the higher the expected maximum speed of the target, the greater the amount of fluctuation in the Doppler frequency contained in the reflected wave from the target, and the shorter the time period with high correlation. In this case, the number of additions Np will be a small value, and the gain improvement effect due to addition in adder 212 will be smaller.

[0060] The Doppler frequency analysis unit 213 calculates CI, which are Nc outputs of the adder 212 obtained at each discrete time k. (z) (k, Nc(w-1)+1)~CI (z) Coherent integration is performed by aligning the timing of discrete time k with (k, Nc×w) as one unit. For example, the Doppler frequency analysis unit 213 performs coherent integration after correcting the phase fluctuation Φ(fs)=2πfs(Tr×Np)ΔΦ corresponding to 2Nf different Doppler frequencies fsΔΦ, as shown in the following equation.

number

[0061] where FT_CI (z) Nant(k, fs, w) is the wth output of the Doppler frequency analysis unit 213 and indicates the coherent integration result of the Doppler frequency fsΔΦ at discrete time k in the Nant-th antenna system processing unit 201, where Nant=1 to Na, fs=-Nf+1,...,0,...,Nf, k=1,...,(Nr+Nu)Ns / No, w is an integer equal to or greater than 1, and ΔΦ is a phase rotation unit.

[0062] As a result, each antenna system processing unit 201 calculates FT_CI, which is a coherent integration result corresponding to 2Nf Doppler frequency components at every discrete time k. (z) Nant (k, -Nf+1,w),…, FT_CI (z) Nant (k, Nf-1, w) is obtained for each Np×Nc period (Tr×Np×Nc) of the radar transmission period Tr, where j is the imaginary unit and z=1,...,Nt.

[0063] When ΔΦ=1 / Nc, the processing of the Doppler frequency analysis unit 213 described above is equivalent to performing a discrete Fourier transform (DFT) on the output of the addition unit 212 with a sampling interval Tm=(Tr×Np) and a sampling frequency fm=1 / Tm.

[0064] Furthermore, by setting Nf to a power of 2, the Doppler frequency analysis unit 213 can apply fast Fourier transform (FFT) processing, which can significantly reduce the amount of calculation processing. In this case, if Nf>Nc, CI is calculated in the region where q>Nc. (z) By performing zero-padding processing such that (k, Nc(w-1)+q)=0, FFT processing can be similarly applied, and the amount of calculation processing can be significantly reduced.

[0065] Furthermore, the Doppler frequency analysis unit 213 may perform a process of sequentially calculating the product-sum operation shown in the above equation (3) without performing an FFT process. In other words, the Doppler frequency analysis unit 213 calculates CI, which are Nc outputs of the adder 212 obtained at each discrete time k. (z)For (k, Nc(w-1)+q+1), the coefficient exp[-j2πf s T r N p qΔφ] may be generated and sequentially processed by product-sum operations, where q=0 to Nc−1.

[0066] In the following description, the w-th output FT_CI obtained by performing the same processing in each of the Na antenna system processing units 201 is referred to as the w-th output FT_CI. (z) 1 (k, fs, w), FT_CI (z) 2 (k, fs, w),…, FT_CI (z) Na The sum of (k, fs, w) is expressed as the virtual receiving array correlation vector h(k, fs, w) as shown in the following equation. The virtual receiving array correlation vector h(k, fs, w) includes Nt × Na elements, which is the product of the number of transmitting antennas Nt and the number of receiving antennas Na. The virtual receiving array correlation vector h(k, fs, w) is used in the description of the process of estimating the direction of a reflected wave signal from a target based on the phase difference between receiving antennas 202, which will be described later. Here, z = 1, ..., Nt, and b = 1, ..., Na.

number

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[0067] The processing in each component of the signal processing unit 207 has been described above.

[0068] The direction estimation unit 214 calculates an array correction value h_cal for the virtual receiving array correlation vector h(k, fs, w) of the w-th Doppler frequency analysis unit 213 output from the antenna system processing units 201-1 to 201-Na. [y] The virtual receiving array correlation vector h _after_cal(k, fs, w) is calculated. The virtual receiving array correlation vector h _after_cal (k, fs, w) are expressed by the following equation, where y = 1, ..., (Nt × Na).

number

[0069] Then, the direction estimator 214 calculates the virtual receiving array correlation vector h _after_cal Using (k, fs, w), direction estimation processing is performed in the horizontal and vertical directions based on the phase difference of the reflected wave signals between the receiving antennas 202. The direction estimation unit 214 calculates a spatial profile by varying the azimuth direction θ and elevation angle direction Φ in the direction estimation evaluation function value P(θ, φ, k, fs, w) within a predetermined angle range, extracts a predetermined number of maximum peaks from the calculated spatial profile in descending order, and sets the azimuth direction and elevation angle direction of the maximum peaks as the direction-of-arrival estimates.

[0070] The evaluation function value P(θ, φ, k, fs, w) can take various values ​​depending on the direction-of-arrival estimation algorithm. For example, the estimation method using an array antenna disclosed in Non-Patent Document 1 may be used.

[0071] (Reference Non-Patent Document 1) Direction-of-arrival estimation using signal subspace modeling, Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1, Publication Year: 1992, Page(s): 64-79

[0072] For example, the beamformer method can be expressed as follows: Other methods such as Capon and MUSIC can also be applied in the same way.

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[0073] where the superscript H is the Hermitian transpose operator. Also, a(θ u , φ v ) is the azimuth direction θ u , elevation direction φ v 1 shows the direction vector of the virtual receiving array for the arriving wave of

[0074] As described above, the direction estimator 214 calculates the wth estimated direction of arrival value, the discrete time k, the Doppler frequency fsΔΦ, and the angle θ u is output as the radar positioning result.

[0075] Here, the direction vector a(θ u , φ v ) is the direction θ u Direction and elevation angle φ v It is a (Nt × Na) order column vector whose elements are the complex response of the virtual receiving array when a reflected wave from the radar transmission signal arrives. The complex response a(θ u , φ v ) represents the phase difference calculated geometrically based on the element spacing between the antennas.

[0076] Also, θ u is obtained by changing the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u is set as follows: θ u =θmin + uβ1, u=0,…, NU NU=floor[(θmax-θmin) / β1]+1 Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0077] Also, φ v is obtained by varying the elevation angle range for estimating the direction of arrival at a predetermined elevation angle interval β2. For example, φ v is set as follows: φ v =φmin + vβ2, v=0,…, NV NV=floor[(φmax-φmin) / β2]+1

[0078] In this embodiment, it is assumed that the direction vector of the virtual receiving array is calculated in advance based on the virtual receiving array arrangements VA#1, ..., VA#(Nt×Na) described later. The elements of the direction vector of the virtual receiving array represent the phase difference calculated geometrically optics based on the element spacing between the antennas in the order of the virtual receiving array arrangement numbers VA#1, ..., VA#(Nt×Na) described later.

[0079] Furthermore, the above-mentioned time information k may be converted into distance information and output. The following formula can be used to convert the time information k into distance information R(k): where Tw represents the code transmission interval, L represents the pulse code length, and C0 represents the speed of light.

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[0080] Furthermore, the Doppler frequency information (fsΔΦ) may be converted into a relative velocity component and output. The Doppler frequency fsΔΦ can be converted into the relative velocity component vd(fs) using the following equation: where λ is the wavelength of the carrier frequency of the RF signal output from the transmission radio unit 107.

number

[0081] [Antenna Arrangement in Radar Device 10] The arrangement of the Nt transmitting antennas 106 and the Na receiving antennas 202 in the radar device 10 having the above configuration will be described below.

[0082] FIG. 6 shows the antenna arrangement of a transmitting array consisting of Nt=2 transmitting antennas 106 (Tx#1, Tx#2), the antenna arrangement of a receiving array consisting of Na=3 receiving antennas 202 (Rx#1, Rx#2, Rx#3), and the antenna arrangement of a virtual receiving array (number of elements: Nt×Na=6) constructed based on these transmitting and receiving array antennas.

[0083] Each of the transmitting antenna 106 and the receiving antenna 202 is configured using sub-array elements each including two antenna elements.

[0084] In addition, the size (width) of the subarray element is D subarry and the desired antenna element spacing at which no grating lobes occur within the radar detection angle range is De. In Figure 6, the size of the sub-array element D subarry is larger than the desired antenna element spacing De (D subarry > De). The desired antenna element spacing De is between 0.5 wavelengths and 0.75 wavelengths.

[0085] Also, the subarray element spacing of the transmitting array antenna is Dt, and the subarray element spacing of the receiving array antenna is Dr. For example, in Fig. 6, the subarray element spacing Dt of the transmitting array antenna is 1.5λ (1.5 wavelengths), and the subarray element spacing Dr of the receiving antenna is 1λ (1 wavelength). In other words, the subarray element spacings Dt and Dr are approximately 1 wavelength (λ) or more.

[0086] In this embodiment, the size D of the sub-array elements is set to be smaller than the desired antenna element spacing De at which no grating lobes occur within the radar detection angle range. subarry When is wide (D subarry In this case, the transmitting array and receiving array are arranged so that the subarray element spacing Dt of the transmitting array antenna and the subarray element spacing Dr of the receiving array antenna satisfy the relationship shown in the following equation: |Dt - Dr| = De (10)

[0087] That is, the absolute value of the difference between the subarray element spacing Dt of the transmitting array antenna and the subarray element spacing Dr of the receiving array antenna is the same as the desired antenna element spacing De.

[0088] FIG. 6 shows, as an example, a case where De=λ / 2, the subarray element spacing of the transmitting array antenna is Dt=1.5λ, and the subarray element spacing of the receiving array antenna is Dr=λ.

[0089] In this case, the element spacing near the center (excluding the ends) of the virtual receiving array becomes the desired antenna element spacing De (=|Dt-Dr|=λ / 2), as shown in Fig. 6. In other words, the virtual receiving array can achieve an array arrangement in which no grating lobes occur within the radar detection angle range.

[0090] Figure 7 shows the directivity pattern (Fourier beam pattern; main beam: 0° direction) for the transmit / receive array antenna arrangement (De=0.5λ, Dt=1.5λ, Dr=λ) shown in Figure 6. As shown in Figure 7, it can be seen that no grating lobes occur within an angular range of ±90° from the main beam direction.

[0091] In this manner, in this embodiment, the transmitting antenna 106 and the receiving antenna 202 are arranged so that the difference (absolute value) between the element spacing of the transmitting array antenna formed from the transmitting antenna 106 and the element spacing of the receiving array antenna formed from the receiving antenna 202 is equal to the desired element spacing at which no grating lobes occur.

[0092] This allows the element spacing of the virtual receiving array, which is configured according to the relative positions of the transmitting antenna 106 and the receiving antenna 202, to be set to a desired element spacing that does not cause grating lobes. This makes it possible to eliminate the occurrence of erroneous detection due to grating lobes when performing direction estimation processing in the direction estimator 214.

[0093] Therefore, according to this embodiment, even when array elements in a subarray configuration are used, it is possible to suppress the occurrence of unnecessary grating lobes and achieve a desired directivity pattern.

[0094] 6 shows an example of a configuration in which array antennas are arranged linearly in the horizontal direction to estimate the direction of arrival in the horizontal direction. However, this embodiment also makes it possible to arrange a virtual receiving array with a desired element spacing in the vertical direction in a similar manner, even when array antennas are arranged linearly in the vertical direction to estimate the direction of arrival in the vertical direction.

[0095] (Variation 1) In variation 1, a case where arrival direction estimation is performed in both the horizontal and vertical directions will be described.

[0096] The transmitting array elements or receiving array elements are arranged two-dimensionally in the vertical and horizontal directions.

[0097] FIG. 8 shows the antenna arrangement of a transmitting array consisting of Nt=6 transmitting antennas 106 (Tx#1 to Tx#6), the antenna arrangement of a receiving array consisting of Na=3 receiving antennas 202 (Rx#1, Rx#2, Rx#3), and the antenna arrangement of a virtual receiving array (number of elements: Nt×Na=18) constructed based on these transmitting and receiving array antennas.

[0098] In FIG. 8, the transmitting array has sub-array elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

[0099] In addition, in Fig. 8, the size of the subarray element in the horizontal direction is D subarry and the size of the sub-array elements in the vertical direction is set to be equal to or smaller than De. In other words, the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and is equal to or smaller than the desired antenna element spacing De in the vertical direction.

[0100] 8, as an example, the desired antenna element spacing De=λ / 2, the horizontal subarray element spacing Dt of the transmitting array antenna is 1.5λ, the vertical element spacing of the transmitting array antenna is De, and the horizontal subarray element spacing Dr=λ of the receiving antenna.

[0101] In this case, the absolute value of the difference between the subarray element spacing Dt of the transmitting array antenna and the subarray element spacing Dr of the receiving array antenna in the horizontal direction is the same as the desired antenna element spacing De. Also, as shown in Fig. 8, the element spacing of the transmitting array antenna in the vertical direction is the same as the desired antenna element spacing De.

[0102] As a result, as shown in FIG. 8, the element spacing near the center (other than the ends) of the virtual receiving array in the horizontal direction becomes the desired antenna element spacing De (=|Dt−Dr|=λ / 2).

[0103] Also, as shown in FIG. 8, the element spacing of the virtual receiving array in the vertical direction is the desired antenna element spacing De, similar to the element spacing of the transmitting array in the vertical direction.

[0104] That is, the virtual receiving array can provide an array arrangement in which no grating lobes occur within the radar detection angle range in either the horizontal or vertical direction.

[0105] When the direction estimation unit 214 estimates the direction of arrival in the horizontal and vertical directions, the azimuth direction θ u and elevation direction φ v is made variable, and the direction estimation evaluation function value P(θ u , φ v , k, fs, w) are calculated, and the azimuth direction and elevation angle direction at which the maximum value is obtained are taken as the estimated direction of arrival value DOA(k, fs, w).

number

[0106] Here, u=1,...,NU. Note that arg max P(x) is an operator whose output value is the value of the domain where the function value P(x) is maximum.

[0107] In addition, the evaluation function value P(θ u , φ v, k, fs, w) vary depending on the direction of arrival estimation algorithm. For example, the estimation method using an array antenna disclosed in the above-mentioned Reference Non-Patent Document 1 may be used. For example, the beamformer method can be expressed as follows. Other methods such as Capon and MUSIC can also be applied in a similar manner.

number

[0108] where the superscript H is the Hermitian transpose operator. Also, a(θ u ,φ v ) is the azimuth direction θ u and elevation direction φ v indicates the direction vector for the incoming wave.

[0109] 9A and 9B show the horizontal and vertical directivity patterns (Fourier beam pattern; main beam: 0° direction) of the transmitting and receiving array antenna arrangement shown in FIG. 8 (when De=0.5λ, Dt=1.5λ, Dr=1λ).

[0110] As shown in Figure 9A, no grating lobes are generated in the horizontal direction within an angular range of ±90° from the main beam direction, and as shown in Figure 9B, a beam pattern is formed that is free of grating lobes in the vertical direction as well.

[0111] By using such an arrangement of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of erroneous detection due to grating lobes in both the horizontal and vertical directions when performing direction estimation processing in the direction estimation unit 214.

[0112] Therefore, according to Variation 1, even when array elements arranged two-dimensionally in a sub-array configuration are used, it is possible to suppress the occurrence of unnecessary grating lobes and achieve a desired directivity pattern.

[0113] In Fig. 8, the horizontal size of the subarray element is D subarry Variation 1 is when the vertical size of the sub-array element is D subarry In this case, the transmitting array should be arranged in the vertical direction so that the difference (absolute value) between the element spacing of the transmitting array antenna and the element spacing of the receiving array antenna is equal to the desired element spacing at which no grating lobes occur.

[0114] (Variation 2) In Variation 2, another example will be described in which arrival direction estimation is performed in both the horizontal and vertical directions.

[0115] Specifically, in a transmitting array antenna, if the horizontal element spacing is Dt (>De) and the vertical element spacing is a desired antenna element spacing De, then in the transmitting array antenna, two subarray element arrays that are adjacent in the vertical direction and aligned in a straight line in the horizontal direction are shifted in the horizontal direction by the same distance as the desired antenna element spacing De.

[0116] FIG. 10 shows the antenna arrangement of a transmitting array consisting of Nt=6 transmitting antennas 106 (Tx#1 to Tx#6), the antenna arrangement of a receiving array consisting of Na=3 receiving antennas 202 (Rx#1, Rx#2, Rx#3), and the antenna arrangement of a virtual receiving array (number of elements: Nt×Na=18) constructed based on these transmitting and receiving array antennas.

[0117] In FIG. 10, the transmitting array has sub-array elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

[0118] In addition, in Fig. 10, the horizontal size of the subarray element is D subarryand the size of the sub-array elements in the vertical direction is set to be equal to or smaller than De. In other words, the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and is equal to or smaller than the desired antenna element spacing De in the vertical direction.

[0119] 10, as in Fig. 8, the desired antenna element spacing De = λ / 2, the horizontal subarray element spacing Dt of the transmitting array antenna is 1.5λ, the vertical element spacing of the transmitting array antenna is De, and the horizontal subarray element spacing Dr = λ of the receiving array antenna.

[0120] As in Variation 1 (Fig. 8), the absolute value of the difference between the subarray element spacing Dt of the transmitting array antenna and the subarray element spacing Dr of the receiving array antenna in the horizontal direction is the same as the desired antenna element spacing De, as shown in Fig. 10. Also, as shown in Fig. 10, the element spacing of the transmitting array antenna in the vertical direction is the same as the desired antenna element spacing De.

[0121] 10, transmitting antennas 106 spaced apart by an antenna element spacing De in the vertical direction of the transmitting array antenna (transmitting antennas 106 adjacent in the vertical direction) are arranged with a horizontal offset equal to the antenna element spacing De. In other words, in the transmitting array antenna, two subarray element arrays that are adjacent in the vertical direction and aligned in a straight line in the horizontal direction are arranged with a horizontal offset equal to the desired element spacing.

[0122] For example, the array of transmitting antennas Tx#1 and Tx#2 (i.e., subarray element array; the same applies below) shown in Fig. 10 is offset from the array of transmitting antennas Tx#3 and Tx#4 adjacent to the array in the vertical direction by the same antenna element spacing De. Similarly, the array of transmitting antennas Tx#3 and Tx#4 is offset from the array of transmitting antennas T#5 and T#6 adjacent to the array in the vertical direction by the same antenna element spacing De in the horizontal direction.

[0123] In Fig. 10, the element spacing near the center (other than the ends) of the virtual receiving array in the horizontal direction is the desired antenna element spacing De (=|Dt-Dr|=λ / 2). Also, as shown in Fig. 10, the element spacing of the virtual receiving array in the vertical direction is the desired antenna element spacing De, just like the element spacing of the transmitting array in the vertical direction. In other words, the virtual receiving array provides an array arrangement in which no grating lobes occur within the radar detection angle range.

[0124] Furthermore, as shown in Fig. 10, in the vertical direction of the virtual receiving array, the arrangement of the array elements in the center (second row) is shifted by De in the horizontal direction compared to the arrangement of the array elements in the other array elements (first and third rows). As a result, in Fig. 10, the spacing between the antenna elements in the two-dimensional plane on which the virtual receiving array is arranged is closer than in Variation 1 (Fig. 8). This makes it possible to reduce the side lobe level in the virtual receiving array.

[0125] 11A and 11B show the horizontal and vertical directivity patterns (Fourier beam pattern; main beam: 0° direction) of the transmitting and receiving array antenna arrangement shown in FIG. 10 (when De=0.5λ, Dt=1.5λ, Dr=λ).

[0126] As shown in Figure 11A, no grating lobes are generated in the horizontal direction within an angular range of ±90° from the main beam direction, and as shown in Figure 11B, a beam pattern is formed in which no grating lobes are generated in the vertical direction either.

[0127] Furthermore, compared with Variation 1 (FIG. 9A), it can be seen that the side lobe level is reduced in the horizontal directivity pattern, as shown in FIG. 11A.

[0128] By using such an arrangement of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of erroneous detection due to grating lobes and side lobes in both the horizontal and vertical directions when performing direction estimation processing in the direction estimation unit 214.

[0129] Therefore, according to Variation 2, even when array elements arranged two-dimensionally in a sub-array configuration are used, it is possible to suppress the occurrence of unnecessary grating lobes and side lobe levels and achieve a desired directivity pattern.

[0130] (Variation 3) In Variation 3, another example will be described in which arrival direction estimation is performed in both the horizontal and vertical directions.

[0131] Specifically, in the transmitting array antenna, the spacing between adjacent subarray element arrays in the vertical direction and aligned in a straight line in the horizontal direction is the desired antenna element spacing De multiplied by a constant α, and two adjacent subarray element arrays in the vertical direction and aligned in a straight line in the horizontal direction are shifted horizontally by a spacing obtained by multiplying the desired antenna element spacing De by a constant β.

[0132] FIG. 12 shows the antenna arrangement of a transmitting array consisting of Nt=6 transmitting antennas 106 (Tx#1 to Tx#6), the antenna arrangement of a receiving array consisting of Na=3 receiving antennas 202 (Rx#1, Rx#2, Rx#3), and the antenna arrangement of a virtual receiving array (number of elements: Nt×Na=18) constructed based on these transmitting and receiving array antennas.

[0133] In FIG. 12, the transmitting array has sub-array elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

[0134] In addition, in Fig. 12, the size of the subarray element in the horizontal direction is D subarryand the size of the sub-array elements in the vertical direction is set to be equal to or smaller than De. In other words, the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and is equal to or smaller than the desired antenna element spacing De in the vertical direction.

[0135] 12, as in Fig. 8, the desired antenna element spacing De=λ / 2, the horizontal subarray element spacing Dt=1.5λ of the transmitting array antenna, and the horizontal subarray element spacing Dr=λ of the receiving array antenna. Also, the horizontal subarray element spacing Dr=λ of the receiving array antenna.

[0136] As in variations 1 and 2 (FIGS. 8 and 10), as shown in FIG. 12, the absolute value of the difference in the horizontal direction between the subarray element spacing Dt of the transmitting array antenna and the subarray element spacing Dr of the receiving array antenna is the same as the desired antenna element spacing De.

[0137] On the other hand, as shown in FIG. 12, the element spacing of the transmitting array antenna in the vertical direction is a spacing αDe obtained by multiplying the desired antenna element spacing De by a constant α.

[0138] 12, transmitting antennas 106 spaced apart by an element spacing αDe in the vertical direction of the transmitting array antenna (transmitting antennas 106 adjacent in the vertical direction) are arranged with a horizontal spacing βDe offset, which is the desired antenna element spacing De multiplied by a constant β. In other words, in the transmitting array antenna, two subarray element arrays that are adjacent in the vertical direction and aligned in a straight line in the horizontal direction are arranged with a horizontal spacing offset of β times the desired element spacing.

[0139] For example, the arrangement of transmitting antennas Tx#1 and Tx#2 shown in Fig. 12 is offset by a distance βDe from the arrangement of transmitting antennas T#3 and Tx#4 that are adjacent to the arrangement in the vertical direction. Similarly, the arrangement of transmitting antennas Tx#3 and Tx#4 is offset by a distance βDe in the horizontal direction from the arrangement of transmitting antennas T#5 and T#6 that are adjacent to the arrangement in the vertical direction.

[0140] For example, α=(3) 0.5 / 2≒0.866 and β=0.5.

[0141] In FIG. 12, the element spacing in the horizontal direction near the center (other than the ends) of the virtual receiving array is the desired antenna element spacing De (=|Dt−Dr|=λ / 2).

[0142] As shown in FIG. 12, the element spacing of the virtual receiving array in the vertical direction is the same as the element spacing of the transmitting array in the vertical direction, αDe(=(3) 0.5 De).

[0143] That is, the virtual receiving array can provide an array arrangement in which no grating lobes occur within the radar detection angle range.

[0144] Furthermore, as shown in Fig. 12, in the vertical direction of the virtual receiving array, the arrangement of the array elements in the center (second row) is shifted by βDe (=0.5De) in the horizontal direction compared to the arrangement of the array elements in the other array elements (first and third rows).

[0145] As a result, in Fig. 12, as with Variation 2 (Fig. 10), the spacing between the antenna elements in the two-dimensional plane on which the virtual receiving array is arranged is closer than in Variation 1 (Fig. 8), which makes it possible to reduce the side lobe level in the virtual receiving array.

[0146] 12, near the center of the virtual receiving array, the spacing between each of three adjacent antenna elements in the two-dimensional plane on which the virtual receiving array is arranged is the desired antenna element spacing De. In other words, the lines connecting three adjacent array elements in the two-dimensional plane on which the virtual receiving array is arranged form an equilateral triangle with one side equal to the antenna element spacing De. Since an equilateral triangular lattice arrangement has better grating lobe suppression performance than a rectangular lattice arrangement with the same aperture length, it is possible to further reduce the levels of grating lobes and side lobes compared to variation 2.

[0147] In other words, the constants α and β need only be set so that the element spacing between three adjacent array elements in the two-dimensional vertical and horizontal directions is the desired antenna element spacing De (shape of an equilateral triangle with one side De).

[0148] 13A and 13B are diagrams showing the arrangement of the transmitting and receiving array antennas shown in FIG. 12 (De=0.5λ, Dt=1.5λ, Dr=1λ, α=(3) 0.5 / 2, β=0.5) in the horizontal and vertical directions (Fourier beam pattern. Main beam: 0° direction).

[0149] As shown in Figure 13A, it can be seen that no grating lobes occur in the horizontal direction within an angular range of ±90° from the main beam direction, and as shown in Figure 13B, it can be seen that a beam pattern is formed that does not generate grating lobes in the vertical direction either.

[0150] Furthermore, compared with Variation 1 (FIG. 9A), it can be seen that the side lobe level is reduced in the horizontal directivity pattern, as shown in FIG. 13A.

[0151] Furthermore, compared to variation 2 (FIG. 11A), as shown in FIG. 13A, it can be seen that the side lobe level that appears in the direction closest to the main lobe (±30° direction in FIG. 13A) in the horizontal directivity pattern is reduced.

[0152] By using such an arrangement of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of erroneous detection due to grating lobes and side lobes in both the horizontal and vertical directions when performing direction estimation processing in the direction estimation unit 214.

[0153] Therefore, according to Variation 3, even when array elements arranged two-dimensionally in a sub-array configuration are used, it is possible to suppress the occurrence of unnecessary grating lobes and side lobe levels and achieve a desired directivity pattern.

[0154] The embodiment according to one aspect of the present disclosure has been described above.

[0155] The operations according to the above-described embodiment and the modifications may be combined as appropriate.

[0156] Furthermore, in the above embodiment, the case where the number of transmitting antennas 106 is Nt=2 or 3 and the number of receiving antennas 202 is Na=3 has been exemplified. However, the number of transmitting antennas 106 Nt and the number of receiving antennas 202 Na are not limited to these numbers.

[0157] In addition, in the above embodiment, the case where the transmitting antenna 106 and the receiving antenna 202 are sub-array elements each consisting of two antenna elements has been described, but the antenna elements that make up each of the transmitting antenna 106 and the receiving antenna 202 may be composed of three or more elements.

[0158] In addition, in the above-described first to third variations of the embodiment, the transmitting array antenna is arranged two-dimensionally in the horizontal and vertical directions, and the receiving array antenna is arranged one-dimensionally in the horizontal direction. However, the present disclosure may also have the receiving array antenna arranged two-dimensionally and the transmitting array antenna arranged one-dimensionally. In this case, the arrangement of the subarray elements in the transmitting array antenna described above may be applied to the arrangement of the subarray elements in the receiving array antenna.

[0159] In the above embodiment, the case where the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and equal to or smaller than the desired antenna element spacing De in the vertical direction has been described, but the size of the antenna elements may be larger than the desired antenna element spacing De in the vertical direction and equal to or smaller than the desired antenna element spacing De in the horizontal direction. In this case, the horizontal and vertical directions of the arrangement of the subarray elements in the above-described transmitting and receiving array antennas may be interchanged.

[0160] Furthermore, in the above embodiment, a case where coded pulse radar is used has been described, but the present disclosure is also applicable to radar systems that use frequency-modulated pulse waves, such as chirp pulse radar.

[0161] In the radar device 10 shown in FIG. 2, the radar transmitter 100 and the radar receiver 200 may be individually arranged in physically separate locations.

[0162] In the above-described radar device, the radar transmitter transmits different code-division multiplexed transmission signals from multiple transmission antennas, and the radar receiver separates and processes the transmission signals. However, the configuration of the radar device is not limited to this, and the radar transmitter may transmit different frequency-division multiplexed transmission signals from multiple transmission antennas, and the radar receiver may separate and process the transmission signals. Similarly, the radar device may transmit time-division multiplexed transmission signals from multiple transmission antennas, and the radar receiver may perform reception processing, and the same effects as those of the above-described embodiments can be obtained.

[0163] Although not shown, the radar device 10 also includes, for example, a central processing unit (CPU), a storage medium such as a read-only memory (ROM) that stores a control program, and a working memory such as a random access memory (RAM). In this case, the functions of the above-described units are realized by the CPU executing the control program. However, the hardware configuration of the radar device 10 is not limited to this example. For example, each functional unit of the radar device 10 may be realized as an integrated circuit (IC). Each functional unit may be individually implemented on a single chip, or a single chip may include some or all of the functional units.

[0164] Summary of this disclosure A radar device according to the present disclosure includes a radar transmitter that transmits radar signals at a predetermined transmission period using a transmitting array antenna, and a radar receiver that receives, using a receiving array antenna, reflected wave signals of the radar signals reflected by a target, wherein the transmitting array antenna and the receiving array antenna each include a plurality of subarray elements, the plurality of subarray elements being arranged on a straight line in a first direction in the transmitting array antenna and the receiving array antenna, each of the subarray elements including a plurality of antenna elements, a size of the subarray elements being larger than a desired antenna element spacing in the first direction, and an absolute value of a difference between the subarray element spacing of the transmitting array antenna and the subarray element spacing of the receiving array antenna being equal to the desired antenna element spacing.

[0165] In the radar device of the present disclosure, the desired antenna element spacing is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths.

[0166] Furthermore, in the radar device according to the present disclosure, in either the transmitting array antenna or the receiving array antenna, the plurality of subarray elements are further arranged in a second direction orthogonal to the first direction, and when the size of the subarray elements is larger than the desired antenna element spacing in the first direction and is equal to or smaller than the desired antenna element spacing in the second direction, an absolute value of the difference between the subarray element spacing of the transmitting array antenna and the subarray element spacing of the receiving array antenna in the first direction is equal to the desired antenna element spacing, and the spacing of the subarray elements in the second direction is equal to the desired antenna element spacing.

[0167] In the radar device of the present disclosure, the subarray elements arranged in the second direction are arranged in the first direction with a shift therebetween by the same interval as the desired antenna element interval.

[0168] Furthermore, in the radar device of the present disclosure, in either the transmitting array antenna or the receiving array antenna, the plurality of subarray elements are further arranged in a second direction orthogonal to the first direction, and when the size of the subarray elements is larger than the desired antenna element spacing in the first direction and equal to or smaller than the desired antenna element spacing in the second direction, the absolute value of the difference between the subarray element spacing of the transmitting array antenna and the subarray element spacing of the receiving array antenna in the first direction is the same as the desired element spacing, the spacing between the subarray elements in the second direction is ((√3) / 2) times the desired antenna element spacing, and the plurality of subarray elements arranged in the second direction are arranged with a spacing shifted by (½) times the desired antenna element spacing in the first direction.

[0169] Although various embodiments (variations) have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above embodiments (variations) may be combined in any manner without departing from the spirit of the disclosure.

[0170] In each of the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0171] Furthermore, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may have inputs and outputs. These may be individually integrated into single chips, or some or all of them may be integrated into a single chip. While the term LSI is used here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the level of integration.

[0172] Furthermore, the method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI.

[0173] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility. [Industrial Applicability]

[0174] The present disclosure is suitable for a radar device that detects a wide angle range. [Explanation of symbols]

[0175] 10 Radar equipment 100 Radar transmitter 200 Radar receiver 300 Reference signal generation section 400 control section 101, 101a Radar transmission signal generation unit 102 Code generator 103 Modulation section 104 LPF 105 Transmitting radio section 106 Transmitting Antenna 111 Code storage unit 112 DA conversion section 201 Antenna system processing unit 202 Receiving antenna 203 Receiving Radio Unit 204 Amplifier 205 Frequency Converter 206 Quadrature Detector 207 Signal Processing Unit 208,209 AD conversion section 210 Separation section 211 Correlation calculation unit 212 Addition section 213 Doppler frequency analysis unit 214 Direction estimation part

Claims

1. a transmitting array antenna; a receiving array antenna; a radar transmitter that transmits a radar signal using the transmitting array antenna; a radar receiving unit that receives, by using the receiving array antenna, a reflected wave signal that is the radar signal reflected by a target; Equipped with the transmitting array antenna includes a plurality of transmitting antennas, the receiving array antenna includes a plurality of receiving antennas, each of the plurality of transmitting antennas is disposed at a different position in each of a first direction and a second direction orthogonal to the first direction; each of the plurality of receiving antennas is disposed at a different position in the first direction; a first interval between two adjacent transmitting antennas among the plurality of transmitting antennas is equal to or greater than one wavelength in the first direction; a distance between two adjacent receiving antennas among the plurality of receiving antennas is equal to or greater than one wavelength in the first direction and is narrower than a first distance between the transmitting antennas; a second interval between two adjacent transmitting antennas among the plurality of transmitting antennas is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths in the second direction; an absolute value of a difference between a first interval between the two adjacent transmitting antennas and an interval between the two adjacent receiving antennas includes an interval that is equal to or greater than 0.5 wavelength and equal to or less than 0.75 wavelength in the first direction; a size in a short side direction of each of the plurality of transmitting antennas is 0.5 wavelengths or less; The size of each of the plurality of receiving antennas in the short side direction is 0.5 wavelengths or less. Radar equipment.

2. Each of the plurality of transmitting antennas includes an equal number of antenna elements. The radar device according to claim 1 .

3. Each of the plurality of receiving antennas includes the same number of antenna elements. The radar device according to claim 1 .

4. the number of the plurality of transmitting antennas is less than the number of the plurality of receiving antennas; 4. A radar device according to claim 1.

5. a first spacing between the two adjacent transmitting antennas is wider than a spacing between the two adjacent receiving antennas; 4. A radar device according to claim 1.

6. The wavelength is determined by the frequency of the radar signal. The radar device according to any one of claims 1 to 5.

7. a first array antenna; a second array antenna; and a radar transmitter that transmits a radar signal using one of the first array antenna and the second array antenna; a radar receiving unit that receives a reflected wave signal, which is the radar signal reflected by a target, using the other of the first array antenna and the second array antenna; Equipped with the first array antenna includes a plurality of first antennas; each of the plurality of first antennas is disposed at a different position in a first direction and a second direction orthogonal to the first direction; the second array antenna includes a plurality of second antennas; each of the plurality of second antennas is disposed at a different position in the first direction; a first distance between two adjacent first antennas among the plurality of first antennas is equal to or greater than one wavelength in the first direction; a distance between two adjacent second antennas among the plurality of second antennas is equal to or greater than one wavelength in the first direction and is narrower than a first distance between the first antennas; a second distance between two adjacent first antennas among the plurality of first antennas is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths in the second direction; an absolute value of a difference between a first interval between two adjacent first antennas and a interval between two adjacent second antennas includes an interval that is equal to or greater than 0.5 wavelength and equal to or less than 0.75 wavelength in the first direction; a size in a short side direction of each of the plurality of first antennas is 0.5 wavelength or less; The size of each of the plurality of second antennas in a short side direction is 0.5 wavelengths or less. Radar equipment.

8. Each of the plurality of first antennas includes an equal number of antenna elements.

8. The radar device according to claim 7.

9. Each of the plurality of second antennas includes the same number of antenna elements. The radar device according to claim 7.

10. the number of antennas in the plurality of first antennas is less than the number of antennas in the plurality of second antennas; 10. A radar device according to claim 7.

11. the interval between the two adjacent first antennas is wider than the interval between the two adjacent second antennas; 10. A radar device according to claim 7.

12. The wavelength is determined by the frequency of the radar signal. A radar device according to any one of claims 7 to 11.

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