JP2024055876A - Radar Equipment - Google Patents

Abstract

To provide a piece of radar equipment capable of achieving a desired directivity pattern while suppressing generation of unnecessary grating lobes even in the case of a sub-array antenna configuration.SOLUTION: Radar equipment includes: multiple transmitting antennas each of which is arranged at a different position in a first direction; and multiple receiving antennas each of which is arranged at a different position in the first direction. A distance between two adjacent transmitting antennas among multiple transmitting antennas is more than or equal to one wavelength in the first direction, and a distance between two adjacent receiving antennas among the multiple receiving antennas is more than or equal to one wavelength in the first direction. A virtual receiving array antenna consisting of a transmitting array antenna and a receiving array antenna has multiple virtual receiving antennas. In the first direction, a spacing between multiple two adjacent virtual receiving antennas includes a spacing equal to a spacing between two adjacent receiving antennas and a spacing that is greater than or equal to 0.5 wavelength and less than or equal to 0.75 wavelength.SELECTED DRAWING: Figure 6

Description

This disclosure relates to a radar device.

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

For example, a pulse radar device that repeatedly transmits pulse waves is known as a radar device. The received signal of a wide-angle pulse radar that detects vehicles/pedestrians in a wide-angle range is a signal that is a mixture of multiple reflected waves from nearby targets (e.g., vehicles) and distant targets (e.g., pedestrians). For this reason, (1) the radar transmitter is required to 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 is required to be configured to have a wide reception dynamic range.

There are two possible configurations for a wide-angle radar device:

The first is a configuration in which pulse waves or modulated waves are mechanically or electronically scanned using a narrow-angle (beam width of a few degrees) directional beam to transmit radar waves, and the narrow-angle directional beam is used to receive the reflected waves. With this configuration, many scans are required to achieve high resolution, which results in poor tracking of fast-moving targets.

The second is a configuration that uses a method (Direction of Arrival (DOA) estimation) in which reflected waves are received by an array antenna consisting of multiple antennas (antenna elements) and the angle of arrival of the reflected waves is estimated by a signal processing algorithm based on the reception phase difference relative to the antenna spacing. In this configuration, even if the scanning interval of the transmission beam in the radar transmitting unit is thinned, the angle of arrival can be estimated in the radar receiving unit, so that the scanning time can be shortened and tracking performance is improved compared to the first configuration. For example, methods of estimating the direction of arrival include Fourier transform based on matrix operations, Capon 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.

In addition, a radar device has been proposed that has 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).

JP 2011-526370 A

Budisin, S.Z., "New complementary pairs of sequences," Electron. Lett., 1990, 26, (13), pp.881-883 Jian Li, Stoica, Petre, "MIMO Radar with Colocated Antennas," Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007

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 (hereafter referred to as array elements) that make up the array antenna is further composed of multiple antenna elements.

It is difficult to arrange the spacing between array antenna elements at intervals narrower than the size of the array elements. However, when using a subarray antenna configuration, the size of the array elements increases, so the spacing between the subarray antennas must be increased, which can result in grating lobes appearing in the directional pattern of the array antenna.

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.

a radar device according to one aspect of the present disclosure comprising a transmitting array antenna, a receiving array antenna, a radar transmitter that transmits a radar signal using the transmitting array antenna, and a radar receiver that receives a reflected wave signal of the radar signal reflected by a target using the receiving array antenna, wherein the transmitting array antenna includes a plurality of transmitting antennas, and the receiving array antenna includes a plurality of receiving antennas, the plurality of transmitting antennas are arranged at different positions in a first direction, the plurality of receiving antennas are arranged at different positions in the first direction, a distance between two adjacent transmitting antennas among the plurality of transmitting antennas is one wavelength or more in the first direction, a distance between two adjacent receiving antennas among the plurality of receiving antennas is one wavelength or more in the first direction, an absolute value of a difference between a distance between the two adjacent transmitting antennas and a distance 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 aspect of the present disclosure includes a first array antenna, a second array antenna, a radar transmitter configured to transmit a radar signal using one of the first array antenna and the second array antenna, and a radar receiver configured to receive a reflected wave signal resulting from the radar signal being reflected by a target using the other of the first array antenna and the second array antenna, wherein the first array antenna includes a plurality of first antennas, each of the plurality of first antennas being disposed at a different position in a first direction, the second array antenna includes a plurality of second antennas, and each of the plurality of second antennas is configured to receive a reflected wave signal from the first array antenna. each of the plurality of first antennas is disposed at a different position in the first direction, a distance between two adjacent first antennas among the plurality of first antennas is one wavelength or more in the first direction, a distance between two adjacent second antennas among the plurality of second antennas is one wavelength or more in the first direction, an absolute value of a difference between a distance between the two adjacent first antennas and a distance between the two adjacent second 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 first antennas and the plurality of second antennas includes a plurality of antenna elements disposed in the first direction.

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.

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.

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 need be provided to obtain one or more identical features.

A diagram showing an example of the configuration of a subarray element. A diagram showing an example of the configuration of an array antenna made up of subarray elements. FIG. 1 is a block diagram showing a configuration of a radar device according to an embodiment of the present disclosure. FIG. 1 is a diagram illustrating an example of a radar transmission signal according to an embodiment of the present disclosure. FIG. 11 is a block diagram showing another configuration of the radar transmission signal generator according to the embodiment of the present disclosure. 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. 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. FIG. 1 illustrates a directional pattern according to an embodiment of the present disclosure. FIG. 1 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. FIG. 13 is a diagram showing a horizontal directivity pattern according to a first variation of an embodiment of the present disclosure; FIG. 13 is a diagram showing a vertical directivity pattern according to a first variation of an embodiment of the present disclosure; FIG. 13 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. FIG. 13 is a diagram showing a horizontal directivity pattern according to a second variation of the embodiment of the present disclosure; FIG. 13 is a diagram showing a vertical directivity pattern according to a second variation of an embodiment of the present disclosure; FIG. 13 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. FIG. 13 is a diagram showing a horizontal directivity pattern according to a third variation of the embodiment of the present disclosure; FIG. 13 is a diagram showing an example of a vertical directivity pattern according to a third variation of an embodiment of the present disclosure;

[How one aspect of the present disclosure was achieved]
Fig. 1A shows an example of an antenna element having a subarray configuration (hereinafter, sometimes referred to as a subarray element). The subarray element shown in Fig. 1A is composed of four antenna elements (2 x 2). In the example shown in Fig. 1A, the size of the subarray element is 0.8 wavelengths in both the horizontal and vertical directions.

Figure 1B shows an example of an array antenna consisting of four subarray elements, each of which is shown in Figure 1A, arranged 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.

For example, the array element spacing (desired element spacing) for preventing grating lobes from occurring within ±90° of the main lobe is 0.5 wavelengths. In the array antenna shown in FIG. 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.

As such, 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. This causes unnecessary grating lobes to appear within a range of ±90° of the main lobe, resulting in a false image when measuring the angle, which can lead to erroneous detection.

Patent Document 1 discloses an array antenna configuration using subarray elements with a width of about d = 1 wavelength. In Patent Document 1, the element spacing of the transmitting antennas Tx0 and Tx1 is 6 wavelengths, and the element spacing of the receiving antennas RX0, RX1, RX2, and RX3 is 1.5 wavelengths ± (λ/8) (λ represents 1 wavelength). Patent Document 1 also provides a configuration in which the transmitting antennas Tx0 and Tx1 are switched in a time-division manner to transmit radar transmission signals, and the receiving antennas RX0, RX1, RX2, and RX3 acquire reception signals in response to the radar transmission signals transmitted from each of the transmitting antennas Tx0 and Tx1.

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

However, in Patent Document 1, the element spacing of the receiving array antenna is 1.5 wavelengths ± λ/8, so grating lobes occur in a direction shifted by about 40° from the main beam direction.

One aspect of the present disclosure suppresses the occurrence of unwanted grating lobes and achieves a desired directivity pattern, even when using array elements in a subarray configuration.

Below, an embodiment of one aspect of the present disclosure will be described in detail with reference to the drawings. Note that in the embodiments, the same components are given the same reference numerals, and their descriptions will be omitted to avoid duplication.

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

The radar device 10 has a radar transmitter 100, a radar receiver 200, and a reference signal generator 300.

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 composed of multiple transmission antennas 106-1 to 106-Nt.

The radar receiver 200 receives the reflected wave signal, which is a radar transmission signal 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 processes the reflected wave signal received by each antenna 202 using a reference signal received from a reference signal generator 300, and detects the presence or absence of a target and estimates its direction. The target is an object that is detected by the radar device 10, and includes, for example, a vehicle or a person.

The reference signal generating unit 300 is connected to each of 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 in common, and synchronizes the processing of the radar transmitting unit 100 and the radar receiving unit 200.

[Configuration of radar transmitter 100]
The radar transmitter 100 has 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 has Nt transmission antennas 106, and each transmission antenna 106 is connected to an individual radar transmission signal generator 101 and radio transmission unit 105.

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 expressed as _rz (k,M)= _Iz (k,M)+ _jQz (k,M), where z represents a number corresponding to each transmitting antenna 106, and z=1,...,Nt. In addition, j represents an imaginary unit, k represents a discrete time, and M represents the ordinal number of the radar transmission period.

Each radar transmission signal generator 101 is composed of 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.

Specifically, the code generation unit 102 generates a code a(z) _n (n=1, ..., L) (pulse code) of a code sequence with a code length L for each radar transmission period Tr. The codes a(z) _n (z=1, ..., Nt) generated in each of the code generation units 102-1 to 102-Nt are low-correlated or uncorrelated codes. Examples of the code sequence include Walsh-Hadamard codes, M-sequence codes, and Gold codes.

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

The LPF 104 outputs the signal components of the modulated signal received from the modulation unit 103 that are below a predetermined limited band to the transmission radio unit 105 as a baseband radar transmission signal.

The zth (z=1, ..., Nt)th transmission radio 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 signal to the zth transmission antenna 106.

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

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, a pulse code sequence is transmitted during the code transmission interval Tw, and the remaining interval (Tr-Tw) is a no-signal interval. Pulse modulation using No samples is performed for one pulse code (a(z) _n ), so that a signal of Nr (=No×L) samples is included in each code transmission interval Tw. That is, the sampling rate in the modulation unit 103 is (No×L)/Tw. It is also assumed that Nu samples are included in the no-signal interval (Tr-Tw).

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, the modulator 103, and the LPF 104 shown in FIG. 2, but instead includes a code memory 111 and a DA converter 112. The code memory 111 pre-stores the code sequence generated by the code generator 102 (FIG. 2) and cyclically reads out the stored code sequences. The DA converter 112 converts the code sequence (digital signal) output from the code memory 111 into an analog signal.

[Configuration of radar receiver 200]
2, the radar receiving unit 200 includes Na receiving antennas 202 forming 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.

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.

Each antenna system processing unit 201 has a receiving radio unit 203 and a signal processing unit 207.

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

The signal processing unit 207 has AD conversion units 208 and 209 and separation units 210-1 to 210-Nt.

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

Here, in the sampling of the AD conversion units 208 and 209, Ns discrete samples are taken per time Tp (=Tw/L) of one subpulse in the radar transmission signal. In other words, the number of oversamples per subpulse is Ns.

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). In the following description, the discrete time k is based (k=1) on the timing when the radar transmission cycle (Tr) starts, and the signal processing unit 207 operates periodically up to k=(Nr+Nu)Ns/No, which is the sample point before the radar transmission cycle Tr ends. In other words, k=1,...,(Nr+Nu)Ns/No. Here, j is the imaginary unit.

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

The correlation calculation unit 211 performs a correlation calculation for each radar transmission period Tr between 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) _n (where z=1,...,Nt, n=1,...,L) having a code length L transmitted by the radar transmission unit 100. For example, the correlation calculation unit 211 performs a sliding correlation calculation between the discrete sample values x(k,M) and the pulse code a(z) _n . For example, a correlation calculation value AC _(z) (k,M) of the sliding correlation calculation at discrete time k in the Mth radar transmission period Tr[M] is calculated based on the following formula:

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

The correlation calculation unit 211 performs correlation calculations over a period of k = 1, ..., (Nr + Nu)Ns/No, for example, according to equation (1).

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) according to the range of the target to be measured by the radar device 10. This allows 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.

As a result, even if the radar transmission signal directly passes through the radar receiving unit 200, the radar device 10 does not perform processing by the correlation calculation unit 211 during the period during which the radar transmission signal passes through (at least a period less than τ1), making it possible to perform measurements that eliminate the effects of pass-through. Furthermore, when limiting the measurement range (range of k), similar processing that limits the measurement range (range of k) can be applied to the processing of the addition unit 212, Doppler frequency analysis unit 213, and direction estimation unit 214 described below. This reduces the amount of processing in each component, and reduces power consumption in the radar receiving unit 200.

The adder 212 adds (coherently integrates) the correlation calculation value AC _(z) (k, _M ) received from the correlation calculator 211 for each discrete time k of the Mth radar transmission cycle Tr over a period (Tr×Np) of a predetermined number (Np) of radar transmission cycles Tr. The addition (coherent integration) process of Np additions over the period (Tr×Np) is expressed by the following equation.

Here, CI _(z) (k,m) represents an addition value of correlation calculation values (hereinafter, may be referred to as a correlation addition value), 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 the adder 212 is regarded as one unit. Also, z=1,...,Nt.

The adder 212 performs addition Np times, with the output of the correlation calculation unit 211 obtained in units of the radar transmission period Tr as one unit. In other words, the adder 212 calculates the correlation value CI _(z) (k,m) for each discrete time k by adding the correlation calculation values AC _(z) (k,Np(m-1)+1) to AC _(z )(k,Np×m) at the same timing for the discrete time k as one unit. 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 arrival distance of the target can be improved.

In order to obtain an ideal addition gain, it is necessary to have a condition where the phase components of the correlation calculation value are aligned to a certain extent in the addition interval of the number of additions Np of the correlation calculation value. In other words, it is preferable to set the number of additions Np based on the assumed maximum moving speed of the target to be measured. This is because the greater the assumed maximum speed of the target, the greater the 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 the adder 212 will be smaller.

The Doppler frequency analysis unit 213 performs coherent integration by aligning the timing of the discrete time k, using CI _(z) (k,Nc(w-1)+1) to CI _(z) (k,Nc×w), which are the Nc outputs of the adder 212 obtained at each discrete time k, 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.

Here, 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 the Nantth discrete time k in the antenna system processing unit 201. Here, 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.

As a result, each antenna system processor 201 obtains FT_CI _(z) ^Nant (k,-Nf+1,w),..., FT_CI _(z) ^Nant (k,Nf-1,w), which are coherent integration results corresponding to 2Nf Doppler frequency components at each discrete time k, for each Np×Nc period (Tr×Np×Nc) of the radar transmission cycle Tr. Note that j is the imaginary unit, and z=1,...,Nt.

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 adder unit 212 with a sampling interval Tm = (Tr × Np) and a sampling frequency fm = 1/Tm.

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

Furthermore, the Doppler frequency analysis unit 213 may perform a process of sequentially calculating the product-sum operation shown in the above formula (3) without performing FFT processing. That is, the Doppler frequency analysis unit 213 may generate coefficients exp[-j2πf s T r N p qΔφ] corresponding to fs=-Nf+1,...,0,...,Nf-1 for CI _(z) (k,Nc(w-1)+q+1), which are Nc outputs _of the _adder unit 212 obtained _at each discrete time k, and perform sequential product-sum operation processing. Here, q=0 to Nc-1.

In the following description, the wth output FT_CI _(z) ¹ (k,fs,w), FT_CI(z) ² (k,fs,w), ..., FT_CI _{( z)} ^Na (k,fs,w) obtained by performing similar processing in each of the Na antenna system processors 201 is expressed as a 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 x 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 to explain the process of estimating the direction of a reflected wave signal from a target based on the phase difference between the receiving antennas 202, which will be described later. Here, z=1, ...,Nt, and b=1, ...,Na.

The above describes the processing in each component of the signal processing unit 207.

The direction estimation unit 214 calculates a virtual receiving array correlation vector h_after_cal(k,fs,w) by correcting the phase deviation and amplitude deviation between the antenna system processing units 201 using the array correction value h_cal _[y] for the virtual receiving array correlation vector h(k,fs,w) of the _wth Doppler frequency analysis unit 213 output from the antenna system processing units 201-1 to 201-Na. The virtual receiving array correlation vector _{h_after_cal} (k,fs,w) is expressed by the following equation, where y=1,...,(Nt×Na).

Then, the direction estimation unit 214 uses the virtual receiving array correlation vector _{h_after_cal} (k,fs,w) to perform direction estimation processing 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 the 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 arrival direction estimate value.

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

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

For example, the beamformer method can be expressed as follows: In addition, other methods such as Capon and MUSIC can also be applied in the same way.

Here, the superscript H is the Hermitian transpose operator, and a(θ _u , φ _v ) represents the direction vector of a virtual receiving array with respect to an arriving wave with an azimuth direction of θ _u and an elevation direction of φ _v .

As described above, the direction estimator 214 outputs the calculated wth arrival direction estimate, discrete time k, Doppler frequency fsΔΦ, and angle _θu as radar positioning results.

Here, the direction vector a( _θu , φv) is an (Nt× _Na ) order column vector whose elements are the complex response of the virtual receiving array when a reflected wave from a radar transmission signal arrives from the azimuth direction _θu and the _elevation direction φv. The complex response a( _θu , _φv ) of the virtual receiving array represents the phase difference calculated geometrically optics based on the element spacing between the antennas.

Moreover, _θu is obtained by varying the azimuth range in which the direction of arrival estimation is performed at a predetermined azimuth interval β _1. For example, _θu is set as follows.
_θu ＝θmin + _uβ1 , u=0,…,NU
NU=floor[(θmax-θmin)/β ₁ ]+1
Here, floor(x) is a function that returns the maximum integer value that does not exceed the real number x.

Also, φ _v is obtained by varying the elevation angle range for estimating the direction of arrival at a predetermined elevation angle interval β _2. For example, φ _v is set as follows.
φ _v ＝φmin + vβ ₂ , v=0,…, NV
NV=floor[(φmax-φmin)/ _β2 ]+1

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 x Na) described later. The elements of the direction vector of the virtual receiving array represent the phase difference calculated geometrically optically at the element spacing between the antennas in the order of the virtual receiving array arrangement numbers VA#1, ..., VA#(Nt x Na) described later.

The above-mentioned time information k may be converted into distance information and output. The following formula may be used to convert the time information k into distance information R(k). Here, Tw represents the code transmission section, L represents the pulse code length, and _C0 represents the speed of light.

In addition, 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: Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmission radio unit 107.

[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.

Figure 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.

Each of the transmitting antenna 106 and the receiving antenna 202 is configured using a sub-array element including two antenna elements.

Also, 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 Fig. 6, the subarray element size D _subarry is larger than the desired antenna element spacing De (D _subarry > De). Note that the desired antenna element spacing De is a value between 0.5 wavelengths and 0.75 wavelengths.

Furthermore, 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.

In this embodiment, when the size D _subarry of the subarray elements is wider than the desired antenna element spacing De at which no grating lobes occur within the radar detection angle range (D _subarry > De), 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 following relationship:
|Dt - Dr | = De (10)

In other words, 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.

Figure 6 shows an example 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.

In this case, as shown in Figure 6, the element spacing near the center of the virtual receiving array (other than the ends) is the desired antenna element spacing De (= |Dt-Dr|=λ/2). In other words, the virtual receiving array provides an array arrangement in which no grating lobes occur within the radar detection angle range.

Figure 7 shows the directivity pattern (Fourier beam pattern; main beam: 0° direction) for the transmit/receive array antenna arrangement shown in Figure 6 (De=0.5λ, Dt=1.5λ, Dr=λ). 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.

In this way, 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 composed of the transmitting antenna 106 and the element spacing of the receiving array antenna composed of the receiving antenna 202 is equal to the desired element spacing at which no grating lobes occur.

In this way, the element spacing of the virtual receiving array configured according to the arrangement relationship between the transmitting antenna 106 and the receiving antenna 202 can be set to the 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 estimation unit 214.

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

Note that FIG. 6 shows an example of a configuration in which the array antennas are arranged linearly in the horizontal direction to estimate the direction of arrival in the horizontal direction. However, in this embodiment, even when the array antennas are arranged linearly in the vertical direction to estimate the direction of arrival in the vertical direction, it is possible to similarly arrange a virtual receiving array with the desired element spacing in the vertical direction in such a way that no grating lobes occur.

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

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

Figure 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.

In Figure 8, the transmitting array has subarray elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

8, the size of the subarray element in the horizontal direction is denoted as D _subarry , and the size of the subarray element in the vertical direction is equal to or less than De. In other words, the size of the antenna elements is greater than the desired antenna element spacing De in the horizontal direction and equal to or less than the desired antenna element spacing De in the vertical direction.

In FIG. 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, and the vertical element spacing of the transmitting array antenna is De. In addition, the horizontal subarray element spacing Dr of the receiving antenna is λ.

In this case, as shown in FIG. 8, 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. Also, as shown in FIG. 8, in the vertical direction, the element spacing of the transmitting array antenna is the same as the desired antenna element spacing De.

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

Also, as shown in FIG. 8, in the vertical direction, the element spacing of the virtual receiving array is the desired antenna element spacing De, which is the same as the vertical element spacing of the transmitting array.

In other words, the virtual receiving array provides an array arrangement in which no grating lobes occur within the radar detection angle range in either the horizontal or vertical direction.

When estimating the direction of arrival in the horizontal and vertical directions in the direction estimation unit 214, the azimuth direction _θu and elevation angle direction _φv are varied as shown in the following equation to calculate a direction estimation evaluation function value P( _θu , _φv , k, fs, w), and the azimuth direction and elevation angle direction which give the maximum value are determined as the direction of arrival estimated value DOA(k, fs, w).

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

The evaluation function value P (θ _u , φ _v , k, fs, w) can 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 the same way.

Here, the superscript H is the Hermitian transpose operator, and a(θ _u , φ _v ) represents a direction vector for an arriving wave in the azimuth direction θ _u and the elevation direction φ _v .

Figures 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 Figure 8 (when De=0.5λ, Dt=1.5λ, Dr=1λ).

As shown in Figure 9A, it can be seen that no grating lobes occur in the horizontal direction within an angular range of ±90° from the main beam direction. Also, as shown in Figure 9B, it can be seen that a beam pattern is formed in which no grating lobes occur in the vertical direction either.

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

Therefore, according to variation 1, even when using array elements arranged in two dimensions in a subarray configuration, it is possible to suppress the occurrence of unnecessary grating lobes and achieve the desired directivity pattern.

8 has been described for the case where the horizontal size of the subarray element is D _subarry (> De), Variation 1 can also be applied to the case where the vertical size of the subarray element is D _subarry (> De). In this case, the transmitting array should be arranged so that the difference (absolute value) between the element spacing of the transmitting array antenna and the element spacing of the receiving array antenna in the vertical direction is equal to the desired element spacing at which no grating lobes occur.

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

Specifically, in a transmitting array antenna, if the horizontal element spacing is Dt (> De) and the vertical element spacing is the 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 spacing as the desired antenna element spacing De.

Figure 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.

In Figure 10, the transmitting array has subarray elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

10, the size of the subarray element in the horizontal direction is denoted as D _subarry , and the size of the subarray element in the vertical direction is equal to or less 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 equal to or less than the desired antenna element spacing De in the vertical direction.

In Fig. 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, and the vertical element spacing of the transmitting array antenna is De. In addition, the horizontal subarray element spacing Dr of the receiving array antenna is λ.

As with variation 1 (Figure 8), as shown in Figure 10, 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 Figure 10, in the vertical direction, the element spacing of the transmitting array antenna is the same as the desired antenna element spacing De.

Furthermore, in FIG. 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 offset in the horizontal direction by the same spacing as 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 offset in the horizontal direction by the same spacing as the desired element spacing.

For example, the array of transmitting antennas Tx#1, Tx#2 shown in FIG. 10 (i.e., subarray element array; the same applies below) and the array of transmitting antennas T#3, Tx#4 adjacent to said array in the vertical direction are arranged with a distance equal to the antenna element spacing De. Similarly, the array of transmitting antennas Tx#3, Tx#4 and the array of transmitting antennas T#5, T#6 adjacent to said array in the vertical direction are arranged with a distance equal to the antenna element spacing De in the horizontal direction.

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

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 in 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.

Figures 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 Figure 10 (when De=0.5λ, Dt=1.5λ, Dr=λ).

As shown in Figure 11A, it can be seen that no grating lobes occur in the horizontal direction within an angular range of ±90° from the main beam direction. Also, as shown in Figure 11B, it can be seen that a beam pattern is formed in which no grating lobes occur in the vertical direction either.

Furthermore, compared to variation 1 (Figure 9A), it can be seen that the side lobe level is reduced in the horizontal directivity pattern, as shown in Figure 11A.

By using such an arrangement of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of false detections 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.

Therefore, according to variation 2, even when using array elements arranged in a two-dimensional subarray configuration, it is possible to suppress the occurrence of unnecessary grating lobes and side lobe levels and achieve the desired directivity pattern.

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

Specifically, in the transmitting array antenna, the spacing between subarray element arrays that are adjacent 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 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 a spacing that is the desired antenna element spacing De multiplied by a constant β.

Figure 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.

In Figure 12, the transmitting array has subarray elements arranged two-dimensionally, two in the horizontal direction and three in the vertical direction.

12 , the size of the subarray element in the horizontal direction is denoted as D _subarry , and the size of the subarray element in the vertical direction is equal to or less 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 equal to or less than the desired antenna element spacing De in the vertical direction.

In Fig. 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.

As with variations 1 and 2 (Figures 8 and 10), as shown in Figure 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.

On the other hand, as shown in FIG. 12, in the vertical direction, the element spacing of the transmitting array antenna is αDe, which is the desired antenna element spacing De multiplied by a constant α.

In addition, in FIG. 12, transmitting antennas 106 separated 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 β times the desired element spacing.

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

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

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

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

In other words, the virtual receiving array provides an array arrangement in which no grating lobes occur within the radar detection angle range.

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 horizontally by βDe (= 0.5De) compared to the arrangement of the array elements in the other array elements (first and third rows).

As a result, in FIG. 12, similar to variation 2 (FIG. 10), the spacing between antenna elements in the two-dimensional plane in which the virtual receiving array is arranged is closer than in variation 1 (FIG. 8). This allows the virtual receiving array to reduce the side lobe level.

As shown in FIG. 12, near the center of the virtual receiving array, the spacing between 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 straight 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 higher 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.

In other words, the constants α and β should be set so that the element spacing between three adjacent array elements in the vertical and horizontal directions is the desired antenna element spacing De (an equilateral triangle with one side De).

13A and 13B 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. 12 (De=0.5λ, Dt=1.5λ, Dr=1λ, α=(3) 0.5} /2, β=0.5), respectively.

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. Also, as shown in Figure 13B, it can be seen that a beam pattern is formed in which no grating lobes occur in the vertical direction either.

Furthermore, compared to variation 1 (Figure 9A), it can be seen that the side lobe level is reduced in the horizontal directivity pattern, as shown in Figure 13A.

In addition, compared to variation 2 (Figure 11A), as shown in Figure 13A, it can be seen that the side lobe level that appears in the direction closest to the main lobe (±30° direction in Figure 13A) in the horizontal directivity pattern has been reduced.

By using such an arrangement of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of false detections 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.

Therefore, according to variation 3, even when using array elements arranged in a two-dimensional subarray configuration, it is possible to suppress the occurrence of unnecessary grating lobes and side lobe levels and achieve the desired directivity pattern.

The above describes one embodiment of the present disclosure.

The operations of the above embodiment and each of the modified examples may be combined as appropriate.

In addition, in the above embodiment, the number of transmitting antennas 106, Nt, is 2 or 3, and the number of receiving antennas 202, Na, is 3. However, the number of transmitting antennas 106, Nt, and the number of receiving antennas 202, Na, are not limited to these numbers.

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 constituting each of the transmitting antenna 106 and the receiving antenna 202 may be composed of three or more elements.

In addition, in the above embodiment variations 1 to 3, the case has been described where 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, in the present disclosure, the receiving array antenna may be arranged two-dimensionally and the transmitting array antenna may be arranged one-dimensionally. In this case, the arrangement of the sub-array elements in the transmitting array antenna described above may be applied to the arrangement of the sub-array elements in the receiving array antenna.

In addition, in the above embodiment, a case has been described in which 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. However, the size of the antenna elements may be larger than the desired antenna element spacing De in the vertical direction and is equal to or smaller than the desired antenna element spacing De in the horizontal direction. In this case, the arrangement of the subarray elements in the above-mentioned transmitting and receiving array antenna may be switched between the horizontal and vertical directions.

In addition, while the above embodiment describes the use of coded pulse radar, the present disclosure can also be applied to radar systems that use frequency-modulated pulse waves, such as chirp pulse radar.

In addition, 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.

In the above description, the radar device is configured such that the radar transmitter transmits different code-division multiplexed transmission signals from multiple transmission antennas, and the radar receiver separates each transmission signal and performs reception processing. 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 separates each transmission signal and performs reception processing. Similarly, the radar device may be configured such that the radar transmitter transmits time-division multiplexed transmission signals from multiple transmission antennas, and the radar receiver performs reception processing, and the same effects as those of the above embodiment can be obtained.

Although not shown, the radar device 10 has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) that stores a control program, and a working memory such as a RAM (Random Access Memory). In this case, the functions of each of the above-mentioned parts 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 part of the radar device 10 may be realized as an IC (Integrated Circuit), which is an integrated circuit. Each functional part may be individually implemented as a single chip, or may be implemented as a single chip that includes some or all of the functional parts.

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 resulting from the radar signals being 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 are arranged on a straight line in a first direction in the transmitting array antenna and the receiving array antenna, each of the subarray elements includes a plurality of antenna elements, a size of the subarray elements is 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 is equal to the desired antenna element spacing.

In addition, in the radar device disclosed herein, the desired antenna element spacing is greater than or equal to 0.5 wavelengths and less than or equal to 0.75 wavelengths.

Furthermore, in the radar device disclosed herein, in either the transmitting array antenna or the receiving array antenna, the multiple subarray elements are further arranged in a second direction perpendicular 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, 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 antenna element spacing, and the spacing of the subarray elements in the second direction is the same as the desired antenna element spacing.

In addition, in the radar device disclosed herein, the subarray elements arranged in the second direction are arranged in the first direction with a shifted distance equal to the desired antenna element spacing.

In addition, in the radar device disclosed herein, in either the transmitting array antenna or the receiving array antenna, the multiple subarray elements are further arranged in a second direction perpendicular 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, 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 of the subarray elements in the second direction is ((√3)/2) times the desired antenna element spacing, and the multiple subarray elements arranged in the second direction are arranged with a spacing shifted by (1/2) times the desired antenna element spacing in the first direction.

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 come up with various modified or revised examples 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 in the above embodiments (variations) may be combined in any manner as long as it does not deviate from the spirit of the disclosure.

In each of the above embodiments, the present disclosure has been described as being configured using hardware, but the present disclosure can also be realized using software in conjunction with hardware.

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 a single chip, or may be integrated into a single chip that includes some or all of them. Here, we refer to it as an LSI, but depending on the level of integration, it may also be called an IC, system LSI, super LSI, or ultra LSI.

In addition, 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.

Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derived technologies, it is possible to integrate functional blocks using that technology. The application of biotechnology, etc. is also a possibility.

This disclosure is suitable for use as a radar device that detects a wide angle range.

REFERENCE SIGNS LIST 10 Radar device 100 Radar transmitter 200 Radar receiver 300 Reference signal generator 400 Control unit 101, 101a Radar transmission signal generator 102 Code generator 103 Modulator 104 LPF
REFERENCE SIGNS LIST 105 Transmitting radio section 106 Transmitting antenna 111 Code storage section 112 DA conversion section 201 Antenna system processing section 202 Receiving antenna 203 Receiving radio section 204 Amplifier 205 Frequency converter 206 Quadrature detector 207 Signal processing section 208, 209 AD conversion section 210 Separation section 211 Correlation calculation section 212 Addition section 213 Doppler frequency analysis section 214 Direction estimation section

Claims (18)

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 a reflected wave signal of the radar signal reflected by a target using the receiving array antenna;
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 a first direction;
each of the plurality of receiving antennas is disposed at a different position in the first direction;
a distance 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;
a virtual receiving array antenna formed by the transmitting array antenna and the receiving array antenna has a plurality of virtual receiving antennas,
In the first direction, the spacing between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas includes a spacing equal to the spacing between the two adjacent receiving antennas and a spacing that is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths.
Radar equipment. an absolute value of a difference between a distance between the two adjacent transmitting antennas and a distance between the two adjacent receiving antennas is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths in the first direction;
2. The radar device according to claim 1. 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.
3. A radar device according to claim 1 or 2. the number of the plurality of transmitting antennas is less than the number of the plurality of receiving antennas,
The distance between the two adjacent transmitting antennas is wider than the distance between the two adjacent receiving antennas.
A radar device according to any one of claims 1 to 3. The number of antennas of the plurality of virtual receiving antennas is:
equal to the number of the plurality of transmitting antennas multiplied by the number of the plurality of receiving antennas,
A radar device according to any one of claims 1 to 4. Among the intervals between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas, an interval equal to the interval between the two adjacent receiving antennas is an interval between two antennas at each end of the plurality of virtual receiving antennas.
A radar device according to any one of claims 1 to 5. Among the intervals between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas, the interval that is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths is
When the number of virtual receiving antennas is even, the distance is between the two central antennas among the plurality of virtual receiving antennas,
When the number of virtual receiving antennas is odd, the spacing is between the central three antennas among the plurality of virtual receiving antennas.
A radar device according to any one of claims 1 to 6. an absolute value of a difference between a distance between the two adjacent transmitting antennas and an aperture length of the receiving array antenna is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths;
A radar device according to any one of claims 1 to 7. The wavelength is determined by the frequency of the radar signal.
A radar device according to any one of claims 1 to 8. 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, by 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;
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 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;
a virtual receiving array antenna formed by the first array antenna and the second array antenna has a plurality of virtual receiving antennas,
In the first direction, the spacing between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas includes a spacing equal to the spacing between the two adjacent receiving antennas and a spacing that is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths.
Radar equipment. an absolute value of a difference between a distance between two adjacent first antennas and a distance between two adjacent second antennas is 0.5 wavelengths or more and 0.75 wavelengths or less in the first direction;
The radar device according to claim 10. At least one of the first and second antennas includes a plurality of antenna elements arranged in the first direction.
The radar device according to claim 10 or 11. the number of antennas of the plurality of first antennas is less than the number of antennas of the plurality of second antennas;
a distance between the two adjacent first antennas is greater than a distance between the two adjacent second antennas;
A radar device according to any one of claims 10 to 12. The number of antennas of the plurality of virtual receiving antennas is:
equal to the number of antennas of the first plurality of antennas multiplied by the number of antennas of the second plurality of antennas;
A radar device according to any one of claims 10 to 13. Among the intervals between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas, an interval equal to the interval between the two adjacent second antennas is an interval between two antennas at each end of the plurality of virtual receiving antennas.
A radar device according to any one of claims 10 to 14. Among the intervals between two adjacent virtual receiving antennas of the plurality of virtual receiving antennas, the interval that is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths is
When the number of virtual receiving antennas is even, the distance is between the two central antennas among the plurality of virtual receiving antennas,
When the number of virtual receiving antennas is odd, the spacing is between the central three antennas among the plurality of virtual receiving antennas.
A radar device according to any one of claims 10 to 15. an absolute value of a difference between a distance between the two adjacent first antennas and an aperture length of the second array antenna is equal to or greater than 0.5 wavelengths and equal to or less than 0.75 wavelengths;
A radar device according to any one of claims 10 to 16. The wavelength is determined by the frequency of the radar signal.
A radar device according to any one of claims 10 to 17.