JP6694027B2 - Radar equipment - Google Patents

Description

  The present disclosure relates to radar devices.

  2. Description of the Related Art In recent years, a radar device using a radar transmission signal having a short wavelength including a microwave or a millimeter wave that can obtain high resolution has been studied. Further, in order to improve the outdoor safety, it is required to develop a radar device that detects an object (target) including a pedestrian in a wide angle range in addition to a vehicle.

  For example, a pulse radar device that repeatedly emits a pulse wave is known as a radar device. A received signal of a wide-angle pulse radar that detects a vehicle / pedestrian in a wide-angle range is a mixture of a plurality of reflected waves from a target (for example, a vehicle) existing at a short distance and a target (for example, a pedestrian) existing at a long distance. It becomes the signal which was done. Therefore, (1) the radar transmitter is required to have a configuration for transmitting a pulse wave or a pulse-modulated wave having an autocorrelation characteristic with a low range side lobe (hereinafter referred to as a low range side lobe characteristic), and (2) The radar receiving unit is required to have a structure having a wide receiving dynamic range.

  The configuration of the wide-angle radar device includes the following two configurations.

  The first is a narrow-angle directional beam that transmits a radar wave by mechanically or electronically scanning a pulse wave or modulated wave with a narrow-angle (beam width of several degrees) directional beam. Is used to receive the reflected wave. With this configuration, many scans are required to obtain high resolution, so the followability with respect to a target moving at high speed deteriorates.

  The second method is to estimate the angle of arrival of the reflected wave using a signal processing algorithm based on the reception phase difference with respect to the antenna spacing, by receiving the reflected wave with an array antenna composed of multiple antennas (antenna elements) (Direction of Arrival). (DOA) estimation) is used. With this configuration, the arrival angle can be estimated in the radar receiving unit even if the scanning interval of the transmission beam in the radar transmitting unit is thinned out, so that the scanning time can be shortened and the tracking performance can be improved compared to the first configuration. Is improved. For example, the DOA estimation method includes Fourier transform based on matrix operation, Capon method and LP (Linear Prediction) method based on inverse matrix operation, or MUSIC (Multiple Signal Classification) and ESPRIT (Estimation of Signal Parameters) based on eigenvalue operation. via Rotational Invariance Techniques).

  In addition, as a radar device, in addition to the radar receiving unit, the radar transmitting unit is also provided with a plurality of antennas (array antennas), and beam scanning is performed by signal processing using the transmitting and receiving array antennas (sometimes referred to as MIMO radar). Has been proposed (for example, see Non-Patent Document 2).

Special table 2011-526370 gazette

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

  By the way, in order to increase the directional gain of the array antenna, a sub-array antenna in which each of the antenna elements (hereinafter, referred to as array element) forming the array antenna further includes a plurality of antenna elements may be used.

  It is difficult to arrange the element spacing of the array antenna at a spacing narrower than the size of the array element. However, when the sub-array antenna configuration is used, the size of the array element becomes large, so it is necessary to widen the interval between the sub-array antennas, and there is a possibility that a grating lobe may be generated on the directional pattern of the array antenna.

  One aspect of the present disclosure provides a radar device capable of suppressing generation of unnecessary grating lobes and realizing a desired directivity pattern even in the case of a sub-array antenna configuration.

The radar device according to one embodiment of the present disclosure, a transmission array antenna, a reception array antenna, a radar transmitter for transmitting the record over Da signal using the transmission array antenna, the radar signal is reflected to the target reflector comprising a radar receiver for receiving with the reception array antenna wave signal, wherein the transmitting array antenna comprises a plurality of transmitting antennas, the reception array antenna includes a plurality of receiving antennas, the plurality of The transmitting antennas are arranged on a straight line in a first direction, the plurality of receiving antennas are arranged on a straight line in the first direction, and the transmitting antenna pitch of the transmitting array antennas is in the first direction. 1 wavelength or more, the reception antenna pitch of the reception array antenna is 1 wavelength or more in the first direction, and The absolute value of the difference between the transmit antennas pitch of antennas and a reception antenna pitch of the reception array antenna, in the first direction, 0.5 wavelength or more and 0.75 wavelengths or less.
A radar device according to another aspect of the present disclosure transmits a first array antenna, a second array antenna, and a radar signal using one of the first array antenna and the second array antenna. A radar transmitting unit; and a radar receiving unit that receives a reflected wave signal in which the radar signal is reflected by a target using the other of the first array antenna and the second array antenna. Array antenna includes a plurality of first antennas, the second array antenna includes a plurality of second antennas, and the plurality of first antennas are arranged on a straight line in a first direction. , The plurality of second antennas are arranged on a straight line in the first direction, and the first antenna pitch of the first array antenna is one wavelength or more in the first direction, The second antenna pitch of the second array antenna is one wavelength or more in the first direction, and the first antenna pitch of the first array antenna and the second antenna pitch of the second array antenna are equal to or larger than one wavelength. The absolute value of the difference from the antenna pitch is 0.5 wavelength or more and 0.75 wavelength or less in the first direction.
A radar device according to still another aspect of the present disclosure is a transmission array antenna, a reception array antenna, a radar transmission unit that transmits a radar signal using the transmission array antenna, and the radar signal is reflected by a target. A radar receiving unit that receives a reflected wave signal using the reception array antenna, the transmission array antenna includes a plurality of transmission antennas, and the reception array antenna includes a plurality of reception antennas. Of the transmitting antennas are arranged on a straight line in the first direction, the plurality of receiving antennas are arranged on a straight line in the first direction, and the transmitting antenna pitch of the transmitting array antenna is set to the first direction. In the first direction, the receiving antenna pitch of the receiving array antenna is 1 wavelength or more, The absolute value of the difference between the receiving antenna pitch of the receiving array antenna and the transmission antenna pitch of transmission array antenna, in the first direction, a pitch grating lobes are not generated.
A radar device according to yet another aspect of the present disclosure transmits a first array antenna, a second array antenna, and a radar signal using one of the first array antenna and the second array antenna. And a radar receiving unit that receives a reflected wave signal obtained by reflecting the radar signal on a target using the other of the first array antenna and the second array antenna. One array antenna includes a plurality of first antennas, the second array antenna includes a plurality of second antennas, and the plurality of first antennas are arranged on a straight line in a first direction. And the plurality of second antennas are arranged on a straight line in the first direction, and the first antenna pitch of the first array antenna is 1 wavelength or more in the first direction. The second antenna pitch of the second array antenna is one wavelength or more in the first direction, and the first antenna pitch of the first array antenna and the second antenna pitch of the second array antenna are The absolute value of the difference from the antenna pitch of 2 is the pitch at which no grating lobe occurs in the first direction.

  Note that these comprehensive or specific aspects may be realized by a system, method, integrated circuit, computer program, or recording medium, and any of the system, apparatus, method, integrated circuit, computer program, and recording medium may be implemented. It may be realized by any combination.

  According to one aspect of the present disclosure, even in the case of a sub array antenna configuration, it is possible to suppress the generation of unnecessary grating lobes and realize a desired directivity pattern.

  Further advantages and effects of one aspect of the present disclosure will be apparent from the specification and the drawings. Such advantages and / or effects are provided by the features described in several embodiments and in the specification and drawings, respectively, but not necessarily all to obtain one or more of the same features. There is no.

Diagram showing a configuration example of a sub-array element The figure which shows the structural example of the array antenna which consists of sub array elements. Block diagram showing the configuration of a radar device according to an embodiment of the present disclosure The figure which shows an example of the radar transmission signal which concerns on one embodiment of this indication. A block diagram showing another configuration of the radar transmission signal generation unit according to the embodiment of the present disclosure. The figure which shows an example of the transmission timing of the radar transmission signal which concerns on one Embodiment of this indication, and a measurement range. The figure which shows the antenna arrangement of the transmission array based on one Embodiment of this indication, a reception array, and a virtual reception array. The figure which shows the directivity pattern which concerns on one Embodiment of this indication. The figure which shows the antenna arrangement of the transmission array, the reception array, and the virtual reception array which concerns on the variation 1 of one embodiment of this indication. The figure which shows the directivity pattern of the horizontal direction which concerns on the variation 1 of one embodiment of this indication. The figure which shows the directivity pattern of the vertical direction which concerns on the variation 1 of one embodiment of this indication. The figure which shows the antenna arrangement of the transmission array which concerns on the variation 2 of one embodiment of this indication, a reception array, and a virtual reception array. The figure which shows the directivity pattern of the horizontal direction which concerns on the variation 2 of one embodiment of this indication. The figure which shows the directivity pattern of the vertical direction which concerns on the variation 2 of one embodiment of this indication. The figure which shows the antenna arrangement of the transmission array which concerns on the variation 3 of one embodiment of this indication, a receiving array, and a virtual receiving array. The figure which shows the directivity pattern of the horizontal direction which concerns on the variation 3 of one Embodiment of this indication. The figure which shows the example of a figure which shows the directivity pattern of the vertical direction which concerns on the variation 3 of one embodiment of this indication.

[Background of One Aspect of the Present Disclosure]
FIG. 1A shows an example of an antenna element having a sub-array structure (hereinafter also referred to as a sub-array element). The sub-array element shown in FIG. 1A is composed of four 2 × 2 antenna elements. In the example shown in FIG. 1A, the size of the sub-array element is 0.8 wavelength in both the horizontal and vertical directions.

  FIG. 1B shows an example of an array antenna configured by arranging four sub-array elements shown in FIG. 1A in series. As shown in FIG. 1B, since the size of each sub-array element is 0.8 wavelength (see FIG. 1A), it is necessary to set the spacing between sub-array elements to be about 1 wavelength or more.

  For example, the array element spacing (desired element spacing) for preventing the generation of grating lobes within ± 90 ° of the main lobe is 0.5 wavelength. In the array antenna shown in FIG. 1B, since the element spacing of the sub-array element is about 1 wavelength or more, it is difficult to set the desired element spacing, and a grating lobe occurs within ± 90 ° of the main lobe. become.

  As described above, when the size of the sub array element is 0.5 wavelength or more, it may be difficult to set the element spacing of the array antenna to 0.5 wavelength. Therefore, an unnecessary grating lobe is generated within the range of ± 90 ° of the main lobe, and a virtual image is generated at the time of measuring the angle, which causes a false detection.

  Here, Patent Document 1 discloses an array antenna configuration using a sub array element having a width of about d = 1 wavelength. In Patent Document 1, the element spacing between the transmitting antennas Tx0 and Tx1 is 6 wavelengths, and the element spacing between the receiving antennas RX0, RX1, RX2, and RX3 is 1.5 wavelengths ± (λ / 8) (λ represents one wavelength). ). Further, in Patent Document 1, the transmitting antennas Tx0, Tx1 are switched in time division to transmit a radar transmitting signal, and the receiving antennas RX0, RX1, RX2, for the radar transmitting signals transmitted from the respective transmitting antennas Tx0, Tx1. The RX3 has a configuration to receive the received signal.

  With such a configuration, a phase change due to a change in the position of the transmission antenna is superimposed on the reception signal acquired by the reception array antenna, so that an effect of virtually increasing the aperture length of the reception antenna can be obtained. Hereinafter, a virtual reception array antenna in which the effective aperture length increases due to the arrangement of antenna elements in the transmission / reception array antenna is called a “virtual reception array”.

  However, in Patent Document 1, since the element spacing of the reception array antenna is 1.5 wavelengths ± λ / 8, a grating lobe occurs in a direction deviated by about 40 ° from the main beam direction.

  One aspect according to the present disclosure suppresses the generation of unnecessary grating lobes and realizes a desired directivity pattern even when an array element having a sub-array configuration is used.

  Hereinafter, embodiments according to one aspect of the present disclosure will be described in detail with reference to the drawings. In addition, in the embodiments, the same components are designated by the same reference numerals, and the description thereof will be omitted to avoid duplication.

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

  The radar device 10 includes 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. Then, the radar transmitter 100 transmits the radar transmission signal at a predetermined transmission cycle by using the transmission array antenna including the plurality of transmission antennas 106-1 to 106-Nt.

  The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a reception array antenna including a plurality of reception antennas 202-1 to 202-Na. The radar receiver 200 uses the reference signal received from the reference signal generator 300 to perform signal processing on the reflected wave signal received by each antenna 202 to detect the presence / absence of a target and estimate the direction. The target is an object to be detected by the radar device 10, and includes, for example, a vehicle or a person.

  The reference signal generator 300 is connected to each of the radar transmitter 100 and the radar receiver 200. The reference signal generation unit 300 supplies the reference signal as the reference signal to the radar transmission unit 100 and the radar reception unit 200 in common, and synchronizes the processes of the radar transmission unit 100 and the radar reception unit 200.

[Structure of Radar Transmitter 100]
The radar transmission unit 100 includes radar transmission signal generation units 101-1 to 101-Nt, transmission radio units 105-1 to 105-Nt, and transmission antennas 106-1 to 106-Nt. That is, the radar transmission unit 100 has Nt transmission antennas 106, and each transmission antenna 106 is connected to the individual radar transmission signal generation unit 101 and transmission radio unit 105.

The radar transmission signal generation unit 101 generates a timing clock by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. Then, the radar transmission signal generation unit 101 repeatedly outputs the radar transmission signal at a predetermined radar transmission cycle (Tr). The radar transmission signal is represented by r _z (k, M) = I _z (k, M) + jQ _z (k, M). Here, z represents the number corresponding to each transmitting antenna 106, and z = 1, ..., Nt. Also, j represents an imaginary unit, k represents a discrete time, and M represents an ordinal number of a radar transmission cycle.

  Each radar transmission signal generation unit 101 includes a code generation unit 102, a modulation unit 103, and an LPF (Low Pass Filter) 104. Hereinafter, each component of the radar transmission signal generation unit 101-z corresponding to the zth (z = 1, ..., Nt) transmission antenna 106 will be described.

Specifically, the code generation unit 102 generates the code a (z) _n (n = 1, ..., L) (pulse code) of the code sequence having the code length L for each radar transmission cycle Tr. For the codes a (z) _n (z = 1, ..., Nt) generated in the code generation units 102-1 to 102-Nt, codes having low correlation or no correlation are used. Examples of the code sequence include Walsh-Hadamard code, M-sequence code, Gold code and the like.

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 to obtain a modulated signal. To the LPF 104.

  The LPF 104 outputs, to the transmission radio unit 105, a signal component within a predetermined limit band of the modulated signal received from the modulation unit 103 as a baseband radar transmission signal.

  The z-th (z = 1, ..., Nt) -th transmission radio section 105 performs frequency conversion on the baseband radar transmission signal output from the z-th radar transmission signal generation section 101 to generate a carrier frequency ( A radar transmission signal in the radio frequency (RF) band is generated, amplified by a transmission amplifier to a predetermined transmission power P [dB], and output to the zth transmission antenna 106.

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

FIG. 3 shows radar transmission signals transmitted from Nt transmission antennas 106 of the radar transmission unit 100. A pulse code sequence having a code length L is included in the code transmission section Tw. In each radar transmission cycle Tr, the pulse code sequence is transmitted during the code transmission section Tw, and the remaining section (Tr-Tw) is a no-signal section. By performing pulse modulation using No samples per pulse code (a (z) _n ), signals of Nr (= No × L) samples are included in each code transmission section Tw. Is included. That is, the sampling rate in the modulator 103 is (No × L) / Tw. Further, it is assumed that Nu signal samples are included in the no-signal section (Tr-Tw).

  The radar transmission unit 100 may include a radar transmission signal generation unit 101a shown in FIG. 4 instead of the radar transmission signal generation unit 101. The radar transmission signal generation unit 101a does not include the code generation unit 102, the modulation unit 103, and the LPF 104 illustrated in FIG. 2, but includes a code storage unit 111 and a DA conversion unit 112 instead. The code storage unit 111 stores in advance the code sequence generated by the code generation unit 102 (FIG. 2), and sequentially reads the stored code sequence cyclically. The DA conversion unit 112 converts the code sequence (digital signal) output from the code storage unit 111 into an analog signal.

[Structure of Radar Receiver 200]
In FIG. 2, the radar receiving unit 200 includes Na receiving antennas 202 and constitutes 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 that 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 reception radio unit 203 and a signal processing unit 207.

  The reception wireless unit 203 includes an amplification unit 204, a frequency converter 205, and a quadrature detector 206. The reception wireless unit 203 generates a timing clock by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies the reception signal received from the reception antenna 202 to a predetermined level, the frequency converter 205 frequency-converts the reception signal in the high frequency band into the baseband band, and the quadrature detector 206 determines the baseband. The received signal in the band band is converted into the received signal in the base band band including the I signal and the Q signal.

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

  The AD converter 208 receives the I signal from the quadrature detector 206, and the AD converter 209 receives the Q signal from the quadrature detector 206. The AD conversion unit 208 converts the I signal into digital data by sampling the baseband signal including the I signal in discrete time. The AD conversion unit 209 converts the Q signal into digital data by sampling the baseband signal including the Q signal in discrete time.

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

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

  The signal processing unit 207 includes Nt demultiplexing units 210, which is equal in number to the number of transmission antennas 106. Each separation unit 210 has a correlation calculation unit 211, an addition unit 212, and a Doppler frequency analysis unit 213. The configuration of the z-th (z = 1, ..., Nt) -th separation unit 210 will be described below.

The correlation calculation unit 211 receives, 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, 209, Correlation calculation is performed with the pulse code a (z) _n (where z = 1, ..., Nt, n = 1, ..., L) of code length L transmitted by the radar transmitter 100. For example, the correlation calculator 211 performs a sliding correlation calculation between the discrete sample value x (k, M) and the pulse code a (z) _n . For example, the correlation calculation value AC _(z) (k, M) of the sliding correlation calculation at the discrete time k in the Mth radar transmission cycle Tr [M] is calculated based on the following equation.

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

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

  The correlation calculation unit 211 is not limited to the case where the correlation calculation is performed on k = 1, ..., (Nr + Nu) Ns / No, and the correlation calculation unit 211 performs measurement according to the existence range of the target to be measured by the radar device 10. The range (ie, the range of k) may be limited. As a result, in the radar device 10, the amount of calculation processing of the correlation calculation unit 211 can be reduced. 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 measurement in the time section corresponding to the code transmission section Tw.

  As a result, in the radar device 10, even when the radar transmission signal directly wraps around the radar reception unit 200, the correlation calculation unit 211 does not perform the process during the wraparound of the radar transmission signal (at least the period of less than τ1). Therefore, it is possible to perform measurement without the influence of wraparound. Further, when the measurement range (range of k) is limited, the measurement range (range of k) is similarly limited for the processing of the adder 212, the Doppler frequency analysis unit 213, and the direction estimation unit 214 described below. The processing described above may be applied. As a result, the amount of processing in each component can be reduced, and the power consumption in the radar receiver 200 can be reduced.

The addition unit 212 uses the correlation calculation value AC _(z) (k, M) received from the correlation calculation unit 211 at each discrete time k of the M-th radar transmission cycle Tr to perform a predetermined number (Np times) of radar transmissions. The correlation calculation value AC _(z) (k, M) is added (coherent integration) over the period (Tr × Np) of the cycle Tr. The addition (coherent integration) process of the addition number Np 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, also referred to as a correlation addition value), Np is an integer value of 1 or more, and m is an addition unit 212. It is an integer of 1 or more indicating the ordinal number of the number of additions when the number of additions Np is one unit. Also, z = 1, ..., Nt.

The adder 212 performs addition Np times using the output of the correlation calculator 211 obtained in the radar transmission period Tr as a unit. That is, the addition unit 212 aligns the timings of the discrete times k with the correlation calculation values AC _(z) (k, Np (m-1) +1) to AC _(z) (k, Np × m) as one unit. Then, the correlation value CI _(z) (k, m) obtained by the addition is calculated for each discrete time k. Thereby, the addition unit 212 can improve the SNR of the reflected wave signal in the range where the reflected wave signal from the target has a high correlation due to the effect of addition of the correlation calculation value over Np times. Therefore, the measurement performance related to the estimation of the arrival distance of the target can be improved.

  In order to obtain an ideal addition gain, it is necessary to have a condition that the phase components of the correlation calculation value are uniform within a certain range in the addition section of the number Np of additions of the correlation calculation value. That is, the number of additions Np is preferably set based on the assumed maximum moving speed of the target to be measured. This is because the greater the assumed maximum velocity of the target, the greater the amount of fluctuation of the Doppler frequency contained in the reflected wave from the target, and the shorter the time period having a high correlation. In this case, the number of additions Np has a small value, and thus the gain improving effect due to the addition in the adder 212 is small.

The Doppler frequency analysis unit 213 outputs N c outputs of the addition unit 212 at each discrete time k, that is, CI _(z) (k, Nc (w-1) +1) to CI _(z) (k, Nc Xw) as one unit, coherent integration is performed at the discrete time k. For example, the Doppler frequency analysis unit 213 corrects the phase fluctuation Φ (fs) = 2πfs (Tr × Np) ΔΦ according to 2Nf different Doppler frequencies fsΔΦ, and then performs coherent integration, as shown in the following equation. ..

Here, FT_CI _(z) ^Nant (k, fs, w) is the w-th output in the Doppler frequency analysis unit 213, and is the Doppler frequency fsΔΦ at the discrete time k in the Nant-th antenna system processing unit 201. The coherent integration result is shown. However, Nant = 1 to Na, fs = -Nf + 1, ..., 0, ..., Nf, k = 1, ..., (Nr + Nu) Ns / No, and w is an integer of 1 or more. , ΔΦ is a phase rotation unit.

Thereby, each antenna system processing unit 201 is a coherent integration result FT_CI _(z) ^Nant (k, -Nf + 1, w), ..., FT_CI ₍ corresponding to 2Nf Doppler frequency components at each discrete time k. _z) ^Nant (k, Nf-1, w) is obtained every Np × Nc period (Tr × Np × Nc) of the radar transmission cycle Tr multiple times. Note that j is an imaginary unit and z = 1, ..., Nt.

  When ΔΦ = 1 / Nc, the processing of the Doppler frequency analysis unit 213 described above is performed by the sampling interval Tm = (Tr × Np) and the sampling frequency fm = 1 / Tm, and the output of the addition unit 212 is subjected to the discrete Fourier transform (DFT). It is equivalent to processing.

Further, 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 greatly reduced. At this time, when Nf> Nc, the FFT is similarly performed by performing the zero-filling process with CI _(z) (k, Nc (w-1) + q) = 0 in the area where q> Nc. Processing can be applied, and the amount of calculation processing can be greatly reduced.

In addition, the Doppler frequency analysis unit 213 may perform the process of sequentially calculating the product-sum calculation shown in the above equation (3) without performing the FFT process. That is, the Doppler frequency analysis unit 213 uses fs for CI _(z) (k, Nc (w-1) + q + 1) which is Nc outputs of the addition unit 212 obtained at each discrete time k. = -Nf + 1, ..., 0, ..., Nf-1 may be generated, and exp [-j2πf _s T _r N _{p q} Δφ] may be generated and the product-sum calculation process may be sequentially performed. Here, q = 0 to Nc-1.

In the following description, the w-th output FT_CI _(z) ¹ (k, fs, w), FT_CI _(z) ² obtained by performing similar processing in each of the Na antenna system processing units 201. (k, fs, w), ..., FT_CI _{(z) A} collection of ^Na (k, fs, w) is expressed as a virtual reception array correlation vector h (k, fs, w) as in the following equation. The virtual reception array correlation vector h (k, fs, w) includes Nt × Na elements, which is the product of the number of transmission antennas Nt and the number of reception antennas Na. The virtual reception array correlation vector h (k, fs, w) will be used in the description of the process of performing direction estimation based on the phase difference between the reception antennas 202 for the reflected wave signal from the target, which will be described later. Here, z = 1, ..., Nt and b = 1, ..., Na.

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

The direction estimation unit 214 has an array correction value h_cal with respect to the virtual reception 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. _The virtual reception array correlation vector _{h_after_cal} (k, fs, w) in which the phase deviation and the amplitude deviation between the antenna system processing units 201 are corrected using _[y] is calculated. The virtual reception array correlation vector _{h_after_cal} (k, fs, w) is expressed by the following equation. Note that y = 1, ..., (Nt × Na).

Then, the direction estimation unit 214 uses the virtual reception array correlation vector _{h_after_cal} (k, fs, w) to estimate the direction in the horizontal direction and the vertical direction based on the phase difference between the reflected wave signals between the reception antennas 202. I do. The azimuth 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, and calculates the calculated spatial profile. A predetermined number of local maximum peaks are extracted in descending order, and the azimuth direction and elevation angle direction of the local maximum peaks are used as the arrival direction estimation values.

  There are various evaluation function values P (θ, φ, k, fs, w) depending on the arrival direction 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 beam former method can be expressed as the following equation. Other methods such as Capon and MUSIC are also applicable.

Here, the superscript H is a Hermitian transpose operator. Further, a (θ _u , φ _v ) represents the direction vector of the virtual reception array for the incoming wave in the azimuth direction θ _u and the elevation angle direction φ _v .

As described above, the direction estimation unit 214 outputs the calculated w-th arrival direction estimated value, the discrete time k, the Doppler frequency fsΔΦ, and the angle θ _u as the radar positioning result.

Here, the directional vector a (θ _u , φ _v ) has elements (Nt × Na) as the complex response of the virtual reception array when the reflected wave for the radar transmission signal arrives from the azimuth θ _u direction and the elevation angle direction φ _v. ) The next column vector. The complex response a (θ _u , φ _v ) of the virtual reception array represents the phase difference calculated geometrically by the element spacing between the antennas.

Further, θ _u is obtained by changing the azimuth range in which the arrival direction is estimated at a predetermined azimuth interval β ₁ . For example, θ _u is set as follows.
θ _u = θ min + _u β ₁ , 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.

Further, φ _v is obtained by changing the elevation angle range in which the arrival direction is estimated at a predetermined elevation angle interval β ₂ . For example, φ _v is set as follows.
φ _v = φ min + v β ₂ , v = 0, ..., NV
NV = floor [(φmax-φmin) / β ₂ ] +1

  In this embodiment, it is assumed that the direction vector of the virtual reception array is calculated in advance based on the virtual reception array arrangement VA # 1, ..., VA # (Nt × Na) described later. The element of the direction vector of the virtual reception array represents the phase difference geometrically calculated by the element spacing between the antennas in the virtual reception array arrangement number order VA # 1, ..., VA # (Nt × Na) described later.

The time information k described above may be converted into distance information and output. The following equation may be used when converting the time information k into the distance information R (k). Here, Tw represents the code transmission section, L represents the pulse code length, and C ₀ represents the speed of light.

Also, the Doppler frequency information (fsΔΦ) may be converted into a relative velocity component and output. When converting the Doppler frequency fsΔΦ into the relative velocity component vd (fs), it can be converted using the following equation. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmission wireless 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.

  FIG. 6 shows an antenna arrangement of a transmitting array composed of Nt = 2 transmitting antennas 106 (Tx # 1, Tx # 2) and Na = 3 receiving antennas 202 (Rx # 1, Rx # 2, Rx #). The antenna arrangement of the receiving array composed of 3) and the antenna arrangement of the virtual receiving array (the number of elements: Nt × Na = 6) formed based on these transmitting and receiving array antennas are shown.

  Each of the transmission antenna 106 and the reception antenna 202 is configured by using a sub array element including two antenna elements.

Further, the size (width) of the sub-array elements is D _subarry, and the desired antenna element interval in which no grating lobe occurs in the radar detection angle range is De. In FIG. 6, the size D _subarry of the _sub array elements is larger than the desired antenna element spacing De (D _subarry > De). As the desired antenna element spacing De, a value of 0.5 wavelength or more and 0.75 wavelength or less is used.

  Further, the sub array element spacing of the transmitting array antenna is Dt, and the sub array element spacing of the receiving array antenna is Dr. For example, in FIG. 6, the sub array element spacing Dt of the transmitting array antenna is set to 1.5λ (1.5 wavelength), and the sub array element spacing Dr of the receiving antenna is set to 1λ (1 wavelength). That is, the sub-array element intervals Dt and Dr are about one wavelength (λ) or more.

In the present embodiment, the subarray element size D _subarry is wider than the desired antenna element spacing De at which no grating lobe occurs in the radar detection angle range (D _subarry > De). In this case, the transmission array and the reception array are arranged so as to satisfy the relationship shown in the following equation between the sub array element spacing Dt of the transmission array antenna and the sub array element spacing Dr of the reception array antenna.
｜ Dt-Dr | = De (10)

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

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

  In this case, as shown in FIG. 6, the element spacing near the center (other than the ends) of the virtual reception array becomes the desired antenna element spacing De (= | Dt-Dr | = λ / 2). That is, in the virtual reception array, an array arrangement in which no grating lobe is generated in the radar detection angle range can be obtained.

  FIG. 7 shows a directivity pattern (Fourier beam pattern; main beam: 0 ° direction) in the transmitting / receiving array antenna arrangement (when De = 0.5λ, Dt = 1.5λ, Dr = λ) shown in FIG. As shown in FIG. 7, it can be seen that no grating lobe is generated in the angle range of ± 90 ° from the main beam direction.

  In this way, in the present embodiment, the difference (absolute value) between the element spacing of the transmission array antenna configured by transmission antenna 106 and the element spacing of the reception array antenna configured by reception antenna 202 is the grating lobe. The transmitting antenna 106 and the receiving antenna 202 are arranged so as to be equal to a desired element interval in which no noise occurs.

  By doing so, it is possible to set the element spacing of the virtual reception array configured according to the positional relationship between the transmission antenna 106 and the reception antenna 202 to a desired element spacing in which no grating lobe occurs. This makes it possible to eliminate the occurrence of erroneous detection due to the grating lobe when performing the direction estimation processing in the direction estimation unit 214.

  Therefore, according to this embodiment, it is possible to suppress the generation of unnecessary grating lobes and realize a desired directivity pattern even when an array element having a sub-array configuration is used.

  In addition, in FIG. 6, in order to perform the arrival direction estimation in the horizontal direction, the configuration in which the array antennas are linearly arranged in the horizontal direction is shown as an example. However, in the present embodiment, even when the array antennas are arranged linearly in the vertical direction in order to perform the DOA estimation in the vertical direction, in the same manner, in the vertical direction, a desired element spacing that does not cause grating lobes is generated. Virtual reception arrays can be arranged.

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

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

  FIG. 8 shows an antenna arrangement of a transmission array composed of Nt = 6 transmission antennas 106 (Tx # 1 to Tx # 6) and Na = 3 reception antennas 202 (Rx # 1, Rx # 2, Rx #). The antenna arrangement of the receiving array composed of 3) and the antenna arrangement of the virtual receiving array (the number of elements: Nt × Na = 18) formed based on these transmitting and receiving array antennas are shown.

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

In FIG. 8, the size of the sub array element in the horizontal direction is D _subarry, and the size of the _sub array element in the vertical direction is De or less. That is, the size of the antenna element is larger than the desired antenna element interval De in the horizontal direction and is equal to or smaller than the desired antenna element interval 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. Further, the sub-array element spacing in the horizontal direction of the receiving antenna is Dr = λ.

  In this case, as shown in FIG. 8, the absolute value of the difference between the sub array element spacing Dt of the transmitting array antenna and the sub array element spacing Dr of the receiving array antenna in the horizontal direction is the same as the desired antenna element spacing De. .. Further, as shown in FIG. 8, the element spacing of the transmission array antenna is the same as the desired antenna element spacing De in the vertical direction.

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

  Further, as shown in FIG. 8, the element spacing of the virtual reception array in the vertical direction is the desired antenna element spacing De, like the vertical element spacing of the transmission array.

  That is, in the virtual reception array, an array arrangement can be obtained in which the grating lobe does not occur in the radar detection angle range in both the horizontal direction and the vertical direction.

When the arrival direction estimation in the horizontal direction and the vertical direction is performed in the direction estimation unit 214, the azimuth direction θ _u and the elevation direction φ _v are made variable as shown in the following equations, and the direction estimation evaluation function value P (θ _u , Φ _v , k, fs, w) is calculated, and the azimuth direction and the elevation direction at which the maximum values are obtained are set as the DOA estimated value DOA (k, fs, w).

  Where 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.

There are various evaluation function values P (θ _u , φ _v , k, fs, w) depending on the arrival direction estimation algorithm. For example, the estimation method using the array antenna disclosed in Reference Non-Patent Document 1 described above may be used. For example, the beam former method can be expressed as the following equation. Other methods such as Capon and MUSIC are also applicable.

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

  9A and 9B show directivity patterns (Fourier beam patterns. Main beam: main beam: the transmission / reception array antenna arrangement (when De = 0.5λ, Dt = 1.5λ, Dr = 1λ) shown in FIG. 8 in the horizontal and vertical directions. 0 ° direction).

  As shown in FIG. 9A, it can be seen that in the horizontal direction, no grating lobe is generated in the angle range of ± 90 ° from the main beam direction. Further, as shown in FIG. 9B, it can be seen that a beam pattern is formed in which no grating lobe is generated even in the vertical direction.

  By using such a layout of the transmitting and receiving array antennas, it is possible to eliminate the occurrence of erroneous detection due to the grating lobe in both the horizontal and vertical directions when performing the direction estimation processing in the direction estimation unit 214.

  Therefore, according to variation 1, even when using an array element that is two-dimensionally arranged and has a sub-array configuration, it is possible to suppress the generation of unnecessary grating lobes and realize a desired directivity pattern.

In FIG. 8, the case where the size of the sub array element in the horizontal direction is D _subarry (> De) has been described. However, in variation 1, the size of the sub array element in the vertical direction is D _subarry (> De). Can be similarly applied. In this case, in the vertical arrangement of the transmission array, the difference (absolute value) between the element spacing of the transmission array antenna and the element spacing of the reception array antenna is equal to the desired element spacing at which no grating lobe occurs, A transmission array may be arranged.

(Variation 2)
In variation 2, another example of performing arrival direction estimation in both the horizontal direction and the vertical direction will be described.

  Specifically, in the transmission array antenna, when the horizontal element spacing is Dt (> De) and the vertical element spacing is the desired antenna element spacing De, in the transmission array antenna, adjacent in the vertical direction, The two sub-array element arrays arranged in a straight line in the horizontal direction are arranged in the horizontal direction with the same spacing as the desired antenna element spacing De.

  FIG. 10 shows an antenna arrangement of a transmission array composed of Nt = 6 transmission antennas 106 (Tx # 1 to Tx # 6) and Na = 3 reception antennas 202 (Rx # 1, Rx # 2, Rx #). The antenna arrangement of the receiving array composed of 3) and the antenna arrangement of the virtual receiving array (the number of elements: Nt × Na = 18) formed based on these transmitting and receiving array antennas are shown.

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

In FIG. 10, the size of the sub array element in the horizontal direction is D _subarry, and the size of the _sub array element in the vertical direction is De or less. That is, the size of the antenna element is larger than the desired antenna element interval De in the horizontal direction and is equal to or smaller than the desired antenna element interval 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 transmission array antenna is 1.5λ, and the vertical element spacing of the transmission array antenna is De. .. Further, the sub-array element interval in the horizontal direction of the receiving array antenna is Dr = λ.

  As in variation 1 (FIG. 8), as shown in FIG. 10, the absolute value of the difference between the sub-array element spacing Dt of the transmitting array antenna and the sub-array element spacing Dr of the receiving array antenna in the horizontal direction is the desired antenna element. It is the same as the interval De. Also, as shown in FIG. 10, the element spacing of the transmission array antenna is the same as the desired antenna element spacing De in the vertical direction.

  Further, in FIG. 10, the transmission antennas 106 that are apart from each other by the antenna element spacing De in the vertical direction of the transmission array antennas (the transmission antennas 106 that are adjacent to each other in the vertical direction) are arranged with the same spacing as the antenna element spacing De in the horizontal direction. It In other words, in the transmission array antenna, two sub-array element arrays that are vertically adjacent to each other and are arranged in a straight line in the horizontal direction are arranged in the horizontal direction at the same intervals as the desired element intervals.

  For example, the array of transmitting antennas Tx # 1 and Tx # 2 shown in FIG. 10 (that is, the sub-array element array; the same applies hereinafter) and the array of transmitting antennas T # 3 and Tx # 4 that are vertically adjacent to the array are described. , And the antenna elements are spaced from each other by the same distance De. Similarly, the array of transmitting antennas Tx # 3, Tx # 4 and the array of transmitting antennas T # 5, T # 6 adjacent to the array in the vertical direction are shifted by the same spacing as the antenna element spacing De in the horizontal direction. It is arranged.

  In FIG. 10, the element spacing near the center of the virtual reception array (other than the ends) in the horizontal direction is the desired antenna element spacing De (= | Dt-Dr | = λ / 2). Further, as shown in FIG. 10, in the vertical direction, the element spacing of the virtual reception array becomes a desired antenna element spacing De, like the vertical element spacing of the transmission array. That is, in the virtual reception array, an array arrangement in which no grating lobe is generated in the radar detection angle range can be obtained.

  Further, as shown in FIG. 10, in the vertical direction of the virtual reception array, the array of array elements in the center (second stage) is compared with the array of array elements in other array elements (first and third stages). Then, they are arranged with a horizontal shift of De. As a result, in FIG. 10, the spacing between the antenna elements in the two-dimensional plane on which the virtual reception array is arranged becomes closer than that in variation 1 (FIG. 8). As a result, the side lobe level can be reduced in the virtual reception array.

  11A and 11B show directivity patterns (Fourier beam patterns. Main beam: main beam: the transmission / reception array antenna arrangement (when De = 0.5λ, Dt = 1.5λ, Dr = λ) shown in FIG. 10 in the horizontal and vertical directions. 0 ° direction).

  As shown in FIG. 11A, it can be seen that in the horizontal direction, no grating lobe is generated in the angle range of ± 90 ° from the main beam direction. Further, as shown in FIG. 11B, it can be seen that a beam pattern in which no grating lobes are generated even in the vertical direction is formed.

  Further, as 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.

  By using such arrangement of the transmitting and receiving array antennas, when performing the direction estimation processing in the direction estimating unit 214, it is possible to eliminate the occurrence of erroneous detection due to the grating lobe and the side lobe in both the horizontal direction and the vertical direction. it can.

  Therefore, according to the variation 2, even when the two-dimensionally arranged array elements having the sub-array configuration are used, it is possible to suppress the generation of unnecessary grating lobes and the side lobe level and realize a desired directivity pattern. it can.

(Variation 3)
In variation 3, another example of performing arrival direction estimation in both the horizontal direction and the vertical direction will be described.

  Specifically, in the transmission array antenna, vertically adjacent, the spacing of the sub-array element array arranged in a straight line in the horizontal direction is the spacing obtained by multiplying the desired antenna element spacing De by a constant α, and the vertical Two sub-array element arrays that are adjacent to each other in the direction and arranged in a straight line in the horizontal direction are arranged in the horizontal direction with an interval deviation obtained by multiplying a desired antenna element interval De by a constant β.

  FIG. 12 shows an antenna arrangement of a transmission array composed of Nt = 6 transmission antennas 106 (Tx # 1 to Tx # 6) and Na = 3 reception antennas 202 (Rx # 1, Rx # 2, Rx #). The antenna arrangement of the receiving array composed of 3) and the antenna arrangement of the virtual receiving array (the number of elements: Nt × Na = 18) formed based on these transmitting and receiving array antennas are shown.

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

In FIG. 12, the size of the sub array element in the horizontal direction is D _subarry, and the size of the _sub array element in the vertical direction is De or less. That is, the size of the antenna element is larger than the desired antenna element interval De in the horizontal direction and is equal to or smaller than the desired antenna element interval De in the vertical direction.

  Similar to FIG. 8, in FIG. 12, 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. And Further, the sub-array element interval in the horizontal direction of the receiving array antenna is Dr = λ.

  As in Variations 1 and 2 (FIGS. 8 and 10), as shown in FIG. 12, the absolute value of the difference between the sub array element spacing Dt of the transmission array antenna and the sub array element spacing Dr of the reception array antenna in the horizontal direction is , The same as the desired antenna element spacing De.

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

  Further, in FIG. 12, the transmission antennas 106 separated from each other in the vertical direction of the transmission array antennas (the transmission antennas 106 adjacent to each other in the vertical direction) have the desired antenna element interval De multiplied in the horizontal direction by a constant β. It is arranged with a gap of βDe. In other words, in the transmission array antenna, two sub-array element arrays that are vertically adjacent to each other and arranged on a straight line in the horizontal direction are arranged in the horizontal direction with a gap of β times the desired element interval.

  For example, the array of transmission antennas Tx # 1 and Tx # 2 shown in FIG. 12 and the array of transmission antennas T # 3 and Tx # 4 that are vertically adjacent to the array are arranged with a gap βDe between them. Similarly, the array of the transmitting antennas Tx # 3 and Tx # 4 and the array of the transmitting antennas T # 5 and T # 6 which are vertically adjacent to the array are arranged with a gap βDe between them in the horizontal direction.

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

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

Further, as shown in FIG. 12, the element spacing of the virtual reception array in the vertical direction is αDe (= (3) ^0.5 De), similarly to the vertical element spacing of the transmission array.

  That is, in the virtual reception array, an array arrangement in which no grating lobe is generated in the radar detection angle range can be obtained.

  Furthermore, as shown in FIG. 12, in the vertical direction of the virtual reception array, the array of array elements in the center (second stage) is compared with the array of array elements in other array elements (first and third stages). Then, they are arranged with a horizontal shift of βDe (= 0.5De).

  As a result, in FIG. 12, as in variation 2 (FIG. 10), the spacing between the antenna elements in the two-dimensional plane on which the virtual reception array is arranged is closer than in variation 1 (FIG. 8). As a result, the side lobe level can be reduced in the virtual reception array.

  Here, as shown in FIG. 12, in the vicinity of the center of the virtual reception array, the respective intervals of the three antenna elements adjacent to each other in the two-dimensional plane on which the virtual reception array is arranged become the desired antenna element interval De. In other words, a straight line connecting three adjacent array elements in the two-dimensional plane on which the virtual reception array is arranged forms an equilateral triangle with one side being the antenna element spacing De. The equilateral triangular lattice arrangement has a higher grating lobe suppressing performance than the rectangular lattice arrangement having the same aperture length, and therefore the level of the grating lobe and the side lobe can be further reduced as compared with the variation 2.

  In other words, the constants α and β are such that the element spacing between three array elements adjacent to each other in two dimensions in the vertical direction and the horizontal direction is the desired antenna element spacing De (a regular triangular shape with one side as De). Should be set to.

FIGS. 13A and 13B show the transmitting and receiving array antenna arrangements (De = 0.5λ, Dt = 1.5λ, Dr = 1λ, α = (3) ^0.5 / 2, β = ^0.5 ) shown in FIG. 12 in the horizontal and vertical directions. The directivity pattern (Fourier beam pattern, main beam: 0 ° direction) is shown.

  As shown in FIG. 13A, it can be seen that in the horizontal direction, no grating lobe is generated in the angle range of ± 90 ° from the main beam direction. Further, as shown in FIG. 13B, it can be seen that a beam pattern is formed in which no grating lobe occurs even in the vertical direction.

  Further, as compared with Variation 1 (FIG. 9A), it is found that the side lobe level is reduced in the horizontal directivity pattern, as shown in FIG. 13A.

  Further, as compared with Variation 2 (FIG. 11A), as shown in FIG. 13A, the side lobe level appearing in the direction closest to the main lobe (± 30 ° direction in FIG. 13A) in the horizontal directivity pattern. It can be seen that it has been reduced.

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

  Therefore, according to the variation 3, even when the two-dimensionally arranged array elements having the sub-array configuration are used, it is possible to suppress the generation of unnecessary grating lobes and the side lobe level and realize a desired directivity pattern. it can.

  The embodiments according to one aspect of the present disclosure have been described above.

  In addition, you may implement combining the operation | movement which concerns on the said embodiment and each modification suitably.

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

  Further, in the above embodiment, the case where the transmitting antenna 106 and the receiving antenna 202 are sub-array elements including two antenna elements has been described, but the number of antenna elements forming each of the transmitting antenna 106 and the receiving antenna 202 is three. It may be composed of one or more elements.

  Further, in the variations 1 to 3 of the above-described embodiment, the case where the transmission array antennas are arranged two-dimensionally in the horizontal direction and the vertical direction and the reception array antennas are arranged one-dimensionally in the horizontal direction has been described. 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.

  Further, in the above embodiment, the size of the antenna element is described as being larger than the desired antenna element interval De in the horizontal direction and not more than the desired antenna element interval De in the vertical direction, but the size of the antenna element is It may be greater than the desired antenna element spacing De in the vertical direction and less than or equal to the desired antenna element spacing De in the horizontal direction. In this case, regarding the arrangement of the sub-array elements in the above-mentioned transmitting / receiving array antenna, the horizontal direction and the vertical direction may be interchanged.

  Further, although cases have been described with the above embodiments where a coded pulse radar is used, the present disclosure is also applicable to a radar system that uses a frequency-modulated pulse wave, such as a chirp pulse radar.

  Further, in the radar device 10 shown in FIG. 2, the radar transmitter 100 and the radar receiver 200 may be individually arranged at physically separated places.

  In the radar device, the radar transmission section outputs different transmission signals code-division-multiplexed from a plurality of transmission antennas, and the radar reception section separates each transmission signal and performs reception processing. The configuration of the radar device is not limited to this, and the radar transmission unit transmits different frequency-division-multiplexed transmission signals from a plurality of transmission antennas, and the radar reception unit separates each transmission signal and performs reception processing. It may be configured. Similarly, the configuration of the radar device may be such that the radar transmitter transmits time-division-multiplexed transmission signals from a plurality of transmission antennas, and the radar receiver performs reception processing. 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) storing a control program, and a working memory such as a RAM (Random Access Memory). . In this case, the function of each unit described above is 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 IC (Integrated Circuit) which is an integrated circuit. Each functional unit may be individually made into one chip, or may be made into one chip so as to include a part or all thereof.

<Summary of the present disclosure>
A radar device according to the present disclosure receives a radar transmission unit that transmits a radar signal using a transmission array antenna at a predetermined transmission cycle, and a reflected wave signal that is a reflection signal reflected from a target using the reception array antenna. A radar receiving section, wherein the transmitting array antenna and the receiving array antenna each include a plurality of sub array elements, and the plurality of sub array elements are the first transmitting array antenna and the receiving array antenna. Arranged on a straight line in a direction, each sub-array element includes a plurality of antenna elements, and the size of the sub-array element is larger than a desired antenna element interval in the first direction, and the sub-array element of the transmission array antenna is The absolute value of the difference between the interval and the sub array element interval of the receiving array antenna is Is the same as the antenna element spacing of Nozomu.

  In the radar device of the present disclosure, the desired antenna element interval is 0.5 wavelength or more and 0.75 wavelength or less.

  In the radar device of the present disclosure, in any one of the transmission array antenna and the reception array antenna, the plurality of sub-array elements are further arranged in a second direction orthogonal to the first direction, and When the size of the sub-array element 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 size of the transmission array antenna in the first direction is smaller than that of the transmission array antenna. The absolute value of the difference between the sub-array element spacing and the sub-array element spacing of the receiving array antenna is the same as the desired antenna element spacing, and the spacing between the sub-array elements in the second direction is the desired antenna element spacing. It is the same as the interval.

  Further, in the radar device of the present disclosure, the plurality of sub-array elements arranged in the second direction are arranged with the same spacing as the desired antenna element spacing shifted in the first direction.

  Further, in the radar device of the present disclosure, in any one of the transmission array antenna and the reception array antenna, the plurality of sub-array elements are further arranged in a second direction orthogonal to the first direction, and When the size of the sub-array element 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 size of the transmission array antenna in the first direction is smaller than that of the transmission array antenna. The absolute value of the difference between the sub-array element spacing and the sub-array element spacing of the receiving array antenna is the same as the desired element spacing, and the spacing of the sub-array elements in the second direction is the desired antenna element spacing. ((√3) / 2) times as long, and the plurality of sub-array elements arranged in the second direction are Serial intervals (1/2) times the desired antenna element spacing in a first direction is arranged to be shifted.

  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 obvious to those skilled in the art that various changes or modifications can be conceived within the scope described in the claims, and naturally, they also belong to the technical scope of the present disclosure. Understood. In addition, the constituent elements in the above-described embodiments (variations) may be arbitrarily combined without departing from the spirit of the disclosure.

  In each of the above-described embodiments, the present disclosure has been described as an example in which the present disclosure is configured using hardware, but the present disclosure can also be implemented by software in cooperation with hardware.

  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 of the functional blocks used in the description of the above embodiments and may have an input and an output. These may be individually made into one chip, or may be made into one chip so as to include some or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI, and it may be realized using a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor (Reconfigurable Processor) capable of reconfiguring connection or setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. The application of biotechnology is possible.

  The present disclosure is suitable as a radar device that detects a wide-angle range.

10 radar device 100 radar transmission unit 200 radar reception unit 300 reference signal generation unit 400 control unit 101, 101a radar transmission signal generation unit 102 code generation unit 103 modulation unit 104 LPF
105 transmission wireless unit 106 transmission antenna 111 code storage unit 112 DA conversion unit 201 antenna system processing unit 202 reception antenna 203 reception wireless unit 204 amplifier 205 frequency converter 206 quadrature detector 207 signal processing unit 208, 209 AD conversion unit 210 separation unit 211 Correlation calculation unit 212 Addition unit 213 Doppler frequency analysis unit 214 Direction estimation unit

Claims (18)

A transmit array antenna,
A receiving array antenna,
A radar transmitter that transmits a radar signal using the transmission array antenna;
A radar receiving unit for receiving a reflected wave signal in which the radar signal is reflected by a target using the reception array antenna,
Equipped with,
The transmission array antenna includes a plurality of transmission antennas,
The receiving array antenna includes a plurality of receiving antennas,
The plurality of transmission antennas are arranged linearly in the first direction,
The plurality of receiving antennas are arranged linearly in said first direction,
The transmission antenna pitch of the transmission array antenna is one wavelength or more in the first direction,
The receiving antenna pitch of the receiving array antenna is one wavelength or more in the first direction,
An absolute value of a difference between a transmission antenna pitch of the transmission array antenna and a reception antenna pitch of the reception array antenna is 0.5 wavelength or more and 0.75 wavelength or less in the first direction,
Radar equipment. The transmission array antenna and the reception array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas,
The virtual reception antenna pitch of the virtual reception array antenna is 0.5 wavelength or more and 0.75 wavelength or less in the first direction,
The radar device according to claim 1. The absolute value of the difference between the transmission antenna pitch of the transmission array antenna and the reception antenna pitch of the reception array antenna is 0.5 wavelength in the first direction,
The radar device according to claim 1. The transmission array antenna and the reception array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas,
A virtual reception antenna pitch of the virtual reception array antenna is 0.5 wavelength in the first direction,
The radar device according to claim 3. Each of the plurality of transmit antennas includes a plurality of transmit antenna elements,
Each of the plurality of receiving antennas includes a plurality of receiving antenna elements,
The radar device according to any one of claims 1 to 4. In the transmission array antenna, the plurality of transmission antennas are further arranged in a second direction orthogonal to the first direction.
The radar device according to any one of claims 1 to 5. In the reception array antenna, the plurality of reception antennas are further arranged in a second direction orthogonal to the first direction.
The radar device according to any one of claims 1 to 5. The wavelength is determined by the frequency of the radar signal,
The radar device according to any one of claims 1 to 7. A first array antenna,
A second array antenna,
A radar transmitter that transmits a radar signal using one of the first array antenna and the second array antenna;
A radar receiver that receives a reflected wave signal in which the radar signal is 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,
The second array antenna includes a plurality of second antennas,
Wherein the plurality of first antenna are arranged linearly in the first direction,
Wherein the plurality of second antennas are arranged linearly in said first direction,
A first antenna pitch of the first array antenna is one wavelength or more in the first direction,
The second antenna pitch of the second array antenna is one wavelength or more in the first direction,
The absolute value of the difference between the first antenna pitch of the first array antenna and the second antenna pitch of the second array antenna is 0.5 wavelength or more and 0.75 wavelength in the first direction. Is less than
Radar equipment. The first array antenna and the second array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas,
The virtual reception antenna pitch of the virtual reception array antenna is 0.5 wavelength or more and 0.75 wavelength or less in the first direction,
The radar device according to claim 9. The absolute value of the difference between the first antenna pitch of the first array antenna and the second antenna pitch of the second array antenna is 0.5 wavelength in the first direction,
The radar device according to claim 9. The first array antenna and the second array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas,
A virtual reception antenna pitch of the virtual reception array antenna is 0.5 wavelength in the first direction,
The radar device according to claim 11. Each of the plurality of first antennas includes a plurality of first antenna elements,
Each of the plurality of second antennas includes a plurality of second antenna elements,
The radar device according to any one of claims 9 to 12. In the first array antenna, the plurality of first antennas are further arranged in a second direction orthogonal to the first direction.
The radar device according to any one of claims 9 to 13. In the second array antenna, the plurality of second antennas are further arranged in a second direction orthogonal to the first direction,
The radar device according to any one of claims 9 to 13. The wavelength is determined by the frequency of the radar signal,
The radar device according to any one of claims 9 to 15. A transmit array antenna,
A receiving array antenna,
A radar transmitter that transmits a radar signal using the transmission array antenna;
A radar receiving unit for receiving a reflected wave signal in which the radar signal is reflected by a target using the reception array antenna,
Equipped with,
The transmission array antenna includes a plurality of transmission antennas,
The receiving array antenna includes a plurality of receiving antennas,
The plurality of transmission antennas are arranged linearly in the first direction,
The plurality of receiving antennas are arranged linearly in said first direction,
The transmission antenna pitch of the transmission array antenna is one wavelength or more in the first direction,
The receiving antenna pitch of the receiving array antenna is one wavelength or more in the first direction,
The absolute value of the difference between the transmission antenna pitch of the transmission array antenna and the reception antenna pitch of the reception array antenna is a pitch at which a grating lobe does not occur within ± 90 ° of the main lobe in the first direction. ,
Radar equipment. A first array antenna,
A second array antenna,
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 in which the radar signal is 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,
The second array antenna includes a plurality of second antennas,
Wherein the plurality of first antenna are arranged linearly in the first direction,
Wherein the plurality of second antennas are arranged linearly in said first direction,
A first antenna pitch of the first array antenna is one wavelength or more in the first direction,
The second antenna pitch of the second array antenna is one wavelength or more in the first direction,
The absolute value of the difference between the first antenna pitch of the first array antenna and the second antenna pitch of the second array antenna is within ± 90 ° of the main lobe in the first direction. The pitch is such that no grating lobes occur,
Radar equipment.

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