JP2021060422A - Radar device - Google Patents

Abstract

To suppress the occurrence of an unnecessary grating lobe and realize a desired directional pattern, even for the case of a sub-array antenna structure.SOLUTION: In a radar device, a plurality of transmit antennas are linearly arranged in a first direction, and a plurality of receive antennas are linearly arranged in the first direction, each of the plurality of transmit antennas including a plurality of transmit antenna elements arranged in a row in a second direction orthogonal to the first direction, each of the plurality of receive antennas including a plurality of receive antenna elements arranged in a row in the second direction orthogonal to the first direction. A transmit antenna pitch of a transmit array antenna is one wavelength or longer in the first direction, and a receive antenna pitch of a receive array antenna is one wavelength or longer in the first direction, the absolute value of a difference between the transmit antenna pitch of the transmit array antenna and the receive antenna pitch of the receive array antenna being 0.5 wavelengths or longer and 0.75 wavelengths or shorter in the first direction.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to a radar device.

In recent years, studies have been conducted on radar devices using radar transmission signals having a short wavelength including microwaves or millimeter waves that can obtain high resolution. Further, in order to improve 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, as a radar device, a pulse radar device that repeatedly transmits a pulse wave is known. The received signal of the wide-angle pulse radar that detects a vehicle / pedestrian in a wide-angle range is a mixture of multiple reflected waves from a target existing at a short distance (for example, a vehicle) and a target existing at a long distance (for example, a pedestrian). It becomes a signal. Therefore, (1) the radar transmitter is required to transmit a pulse wave or a pulse-modulated wave having an autocorrelation characteristic (hereinafter referred to as a low-range sidelobe characteristic) that has a low range sidelobe, and (2). The radar receiver is required to have a configuration having a wide reception dynamic range.

The following two configurations can be mentioned as the configuration of the wide-angle radar device.

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

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

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

Japanese Patent Application Laid-Open No. 2011-526370

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 directivity gain of the array antenna, a sub-array antenna in which each of the antenna elements (hereinafter, referred to as array elements) constituting the array antenna is further composed of 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 that it is necessary to widen the distance between the sub-array antennas, and a grating lobe may occur on the directivity pattern of the array antenna.

One aspect of the present disclosure provides a radar device capable of suppressing the 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 aspect of the present disclosure includes a transmitting array antenna, a receiving array antenna, a radar transmitting unit that transmits a radar signal using the transmitting array antenna, and a reflected wave signal in which the radar signal is reflected by a target. The receiving array antenna includes a plurality of transmitting antennas, the receiving array antenna includes a plurality of receiving antennas, and the plurality of transmitting antennas are provided. 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 1 in the first direction. It is equal to or more than a wavelength, and the receiving antenna pitch of the receiving array antenna is one wavelength or more in the first direction, and the absolute difference between the transmitting antenna pitch of the transmitting array antenna and the receiving antenna pitch of the receiving array antenna is absolute. The values are 0.5 wavelength or more and 0.75 wavelength or less in the first direction.
The radar device according to another aspect of the present disclosure transmits a radar signal by using one of the first array antenna, the second array antenna, and the first array antenna and the second array antenna. The first includes a radar transmitting unit and a radar receiving unit that receives a reflected wave signal from which the radar signal is reflected on a target by using the other of the first array antenna and the second array antenna. The 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 the 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 of the second array antenna are The absolute value of the difference from the pitch is 0.5 wavelength or more and 0.75 wavelength or less in the first direction.
The radar device according to still another aspect of the present disclosure includes a transmitting array antenna, a receiving array antenna, a radar transmitting unit that transmits a radar signal using the transmitting array antenna, and the radar signal reflected by a target. A radar receiving unit that receives a reflected wave signal by using the receiving array antenna, the transmitting array antenna includes a plurality of transmitting antennas, and the receiving array antenna includes a plurality of receiving antennas. The transmitting antenna is 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 in the first direction. In the above, the receiving antenna pitch of the receiving array antenna is one wavelength or more, and the receiving antenna pitch of the receiving array antenna is one wavelength or more in the first direction, and the transmitting antenna pitch of the transmitting array antenna and the receiving antenna pitch of the receiving array antenna The absolute value of the difference is the pitch at which the grating lobe does not occur in the first direction.
The radar device according to still another aspect of the present disclosure transmits a radar signal by using one of the first array antenna, the second array antenna, and the first array antenna and the second array antenna. A radar transmitting unit for receiving the radar signal, and a radar receiving unit for receiving the reflected wave signal reflected by the target by using the other of the first array antenna and the second array antenna. The array antenna 1 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 the 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 The absolute value of the difference from the antenna pitch is the pitch at which the grating lobe does not occur in the first direction.

It should be noted that these comprehensive or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium, and any of the system, a device, a method, an integrated circuit, a computer program, and a recording medium. It may be realized by various combinations.

According to one aspect of the present disclosure, even in the case of the 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 in one aspect of the present disclosure will be apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and features described in the specification and drawings, respectively, but not all need to be provided in order to obtain one or more identical features. There is no.

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

[Background to one aspect of this disclosure]
FIG. 1A shows an example of an antenna element having a sub-array configuration (hereinafter, may be referred to as a sub-array element). The sub-array element shown in FIG. 1A is composed of four 2 × 2 antenna elements. Further, in the example shown in FIG. 1A, the size of the sub-array element is set to 0.8 wavelength in both the horizontal direction and the vertical direction.

FIG. 1B shows an example of an array antenna in which four sub-array elements shown in FIG. 1A are arranged 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 take an interval of about 1 wavelength or more as an interval between the sub-array elements.

For example, the array element spacing (desired element spacing) for not generating a grating lobe within the range of ± 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 elements is about one wavelength or more, it is difficult to set the desired element spacing, and a grating lobe is generated within the range of ± 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 angle measurement, which causes erroneous detection.

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

With such a configuration, since the phase change due to the change in the position of the transmitting antenna is superimposed on the received signal acquired by the receiving array antenna, the effect of virtually increasing the aperture length of the receiving antenna can be obtained. Hereinafter, a virtual reception array antenna whose effective aperture length is increased by the arrangement of antenna elements in the transmission / reception array antenna is referred to as a “virtual reception array”.

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

One aspect of 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 the embodiment, the same components are designated by the same reference numerals, and the description thereof will be duplicated and will be omitted.

[Radar device configuration]
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 transmitting unit 100, a radar receiving unit 200, and a reference signal generating unit 300.

The radar transmission unit 100 generates a high-frequency radar signal (radar transmission signal) based on the reference signal received from the reference signal generation unit 300. Then, the radar transmission unit 100 transmits a radar transmission signal at a predetermined transmission cycle by using a transmission array antenna composed of a plurality of transmission antennas 106-1 to 106-Nt.

The radar receiving unit 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a receiving array antenna composed of a plurality of receiving antennas 202-1 to 202-Na. The radar receiving unit 200 processes the reflected wave signal received by each antenna 202 by using the reference signal received from the reference signal generating unit 300, detects the presence or absence of a target, estimates the direction, and the like. 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 generation unit 300 is connected to each of the radar transmission unit 100 and the radar reception unit 200. The reference signal generation unit 300 commonly supplies a reference signal as a reference signal to the radar transmission unit 100 and the radar reception unit 200, and synchronizes the processing of the radar transmission unit 100 and the radar reception unit 200.

[Structure of radar transmitter 100]
The radar transmission unit 100 includes a radar transmission signal generation unit 101-1 to 101-Nt, a transmission radio unit 105-1 to 105-Nt, and a transmission antenna 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 an individual radar transmission signal generation unit 101 and a transmission radio unit 105, respectively.

The radar transmission signal generation unit 101 generates a timing clock obtained by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number of times, 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 in 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 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 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 in the radar transmission signal generation unit 101-z corresponding to the z-th (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 each code generation unit 102-1 to 102-Nt, codes that are low-correlated or uncorrelated with each other are used. Examples of the code sequence include a Walsh-Hadamard code, an M-sequence code, and a Gold code.

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 performs a modulation signal. Is output to LPF104.

The LPF 104 outputs a signal component below a predetermined limiting band among the modulated signals received from the modulation unit 103 to the transmission radio unit 105 as a baseband radar transmission signal.

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

The z-th (z = 1, ..., Nt) th-th transmitting antenna 106 radiates a radar transmission signal output from the z-th-th transmitting 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. Of each radar transmission cycle Tr, a pulse code sequence is transmitted during the code transmission section Tw, and the remaining section (Tr-Tw) is a non-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 modulation unit 103 is (No × L) / Tw. Further, it is assumed that the non-signal section (Tr-Tw) includes Nu samples.

The radar transmission unit 100 may include the 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 have the code generation unit 102, the modulation unit 103, and the LPF 104 shown in FIG. 2, but instead includes the code storage unit 111 and the DA conversion unit 112. The code storage unit 111 stores in advance the code sequence generated by the code generation unit 102 (FIG. 2), and sequentially reads out the stored code sequence in a cyclic manner. 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. Further, the radar receiving unit 200 has Na antenna system processing units 201-1 to 201-Na and a direction estimation 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 receiving signal.

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

The receiving radio unit 203 includes an amplification unit 204, a frequency converter 205, and an orthogonal detector 206. The reception radio unit 203 generates a timing clock obtained by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number of times, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies the received signal received from the receiving antenna 202 to a predetermined level, the frequency converter 205 frequency-converts the received signal in the high frequency band into the base band, and the orthogonal detector 206 frequency-converts the received signal into the base band. The band band received signal is converted into a base band band received signal 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.

An I signal is input from the orthogonal detector 206 to the AD conversion unit 208, and a Q signal is input from the orthogonal detector 206 to the AD conversion unit 209. The AD conversion unit 208 converts the I signal into digital data by sampling the baseband signal including the I signal at a discrete time. The AD conversion unit 209 converts the Q signal into digital data by sampling the baseband signal including the Q signal at a 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, the discrete time of the Mth radar transmission period Tr [M] as the output of the AD converters 208 and 209 is used by using the I signal Ir (k, M) and the Q signal Qr (k, M). The baseband received signal at k is expressed as a complex signal x (k, M) = Ir (k, M) + jQr (k, M). Further, in the following, the discrete time k is based on the timing at which the radar transmission cycle (Tr) starts (k = 1), and the signal processing unit 207 is a sample point before the radar transmission cycle Tr ends. = (Nr + Nu) Operates periodically up to Ns / No. That is, k = 1, ..., (Nr + Nu) Ns / No. Here, j is an imaginary unit.

The signal processing unit 207 includes Nt separation units 210 equal to the number of systems corresponding to the number of transmitting antennas 106. Each separation unit 210 includes a correlation calculation unit 211, an addition unit 212, and a Doppler frequency analysis unit 213. Hereinafter, the configuration of the z-th (z = 1, ..., Nt) th separation unit 210 will be described.

The correlation calculation unit 211 includes discrete sample values x (k, M) including discrete sample values Ir (k, M) and Qr (k, M) received from AD conversion units 208 and 209 for each radar transmission cycle Tr. _{Correlation calculation is performed with the pulse code a (z) n} (where z = 1, ..., Nt, n = 1, ..., L) of the 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 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 equation, the asterisk (*) represents the complex conjugate operator.

For example, the correlation calculation unit 211 performs the correlation calculation over a period of k = 1, ..., (Nr + Nu) Ns / No 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 measurement is performed 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 the measurement in the time section corresponding to the code transmission section Tw.

As a result, even if the radar transmission signal wraps around the radar receiving unit 200 directly, the radar device 10 does not perform processing by the correlation calculation unit 211 during the period when the radar transmission signal wraps around (at least a 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 addition unit 212, the Doppler frequency analysis unit 213, and the direction estimation unit 214 described below. The processing that has been performed may be applied. As a result, the amount of processing in each component can be reduced, and the power consumption in the radar receiving unit 200 can be reduced.

_{The addition unit 212 uses the correlation calculation values AC (z)} (k, M) received from the correlation calculation unit 211 for each discrete time k of the Mth radar transmission cycle Tr to transmit radar a predetermined number of times (Np times). _{The correlation calculation values AC (z)} (k, M) are added (coherent integration) over the period of the period Tr (Tr × Np). 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 the addition value of the correlation calculation value (hereinafter, may be referred to as the correlation addition value), Np is an integer value of 1 or more, and m is the addition unit 212. It is an integer of 1 or more indicating the order of the number of additions when the number of additions Np is one unit. Also, z = 1, ..., Nt.

The addition unit 212 performs Np additions using the output of the correlation calculation unit 211 obtained in units of the radar transmission cycle Tr as one unit. That is, the addition unit 212 _{aligns the timing of the discrete time k with the correlation calculation values AC (z)} (k, Np (m-1) +1) to AC _(z) (k, Np × m) as one unit. _{Calculate the correlation value CI (z)} (k, m) added by the above for each discrete time k. As a result, the addition unit 212 can improve the SNR of the reflected wave signal in the range in which the reflected wave signal from the target has a high correlation due to the effect of adding the correlation calculation value over Np times. Therefore, it is possible to improve the measurement performance regarding the estimation of the arrival distance of the target.

In order to obtain the ideal addition gain, it is necessary to have a condition in which the phase components of the correlation calculation values are aligned within a certain range in the addition interval of the number of additions of the correlation calculation values Np. 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 larger the assumed maximum velocity of the target, the larger the fluctuation amount 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, since the number of additions Np is a small value, the gain improvement effect due to the addition by the addition unit 212 becomes small.

Doppler frequency analyzing unit 213, a Nc-number of the output of the adder 212 obtained for each discrete time _{k CI (z) (k,} Nc (w-1) +1) ~CI (z) (k, Nc Coherent integration is performed with the timing of the discrete time k aligned with xw) as one unit. 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 as shown in the following equation, and then performs coherent integration. ..

Here, FT_CI _(z) ^Nant (k, fs, w) is the w-th output in the Doppler frequency analysis unit 213, and the Doppler frequency fsΔΦ in 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.

As a result, each antenna system processing unit 201 can perform coherent integration results corresponding to 2 Nf Doppler frequency components for each discrete time k. FT_CI _(z) ^Nant (k, -Nf + 1, w), ..., FT_CI _{( z)} ^Nant (k, Nf-1, w) is obtained every multiple times Np × Nc period (Tr × Np × Nc) of Tr between radar transmission cycles. 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 sets the sampling interval Tm = (Tr × Np), the sampling frequency fm = 1 / Tm, and the output of the addition unit 212 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 a fast Fourier transform (FFT) process, and can greatly reduce the amount of arithmetic processing. At this time, when Nf> Nc _{, the FFT is similarly performed by performing zero-filling processing in which CI (z)} (k, Nc (w-1) + q) = 0 in the region where q> Nc. Processing can be applied, and the amount of arithmetic processing can be greatly reduced.

Further, the Doppler frequency analysis unit 213 may perform a process of sequentially calculating the product-sum operation shown in the above equation (3) without performing the FFT process. _{That is, the Doppler frequency analysis unit 213 fs with respect to CI (z)} (k, Nc (w-1) + q + 1), which is the output of Nc of the addition unit 212 obtained for each discrete time k. _{The coefficient exp [-j 2πf s Tr} N _{p q} Δφ] corresponding to = -Nf + 1, ..., 0, ..., Nf-1 may be generated and the product-sum operation process may be performed sequentially. Here, q = 0 to Nc-1.

_{In the following description, the wth output FT_CI (z)} ¹ (k, fs, w), FT_CI _(z) ² obtained by performing the same processing in each of the Na antenna system processing units 201. The sum of (k, fs, w),…, FT_CI _(z) ^Na (k, fs, w) is expressed as the virtual reception array correlation vector h (k, fs, w) as shown in the following equation. The virtual reception array correlation vector h (k, fs, w) includes Nt × Na elements which are the products of the number of transmitting antennas Nt and the number of receiving antennas Na. The virtual reception array correlation vector h (k, fs, w) is used in a description of a process for estimating the direction of the reflected wave signal from the 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 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. _{Using [y] , 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 is calculated. The virtual reception array correlation vector h _{_after_cal} (k, fs, w) is expressed by the following equation. It should be noted 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 perform horizontal and vertical direction estimation processing based on the phase difference of the reflected wave signals between the receiving antennas 202. I do. The azimuth estimation unit 214 calculates a spatial profile in which the directional direction θ and the elevation angle direction Φ in the directional estimation evaluation function value P (θ, φ, k, fs, w) are variable within a predetermined angle range, and the calculated spatial profile is calculated. A predetermined number of the maximum peaks are extracted in descending order, and the directional direction and the elevation angle direction of the maximum peaks are used as the estimated values in the arrival direction.

There are various evaluation function values P (θ, φ, k, fs, w) depending on the arrival direction estimation algorithm. For example, an 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 the following equation. Other methods such as Capon and MUSIC can be applied as well.

Here, the superscript H is the Hermitian transpose operator. Further, a (θ _u , φ _v ) indicates the direction vector of the virtual reception array with respect to the incoming wave in the directional 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 direction vector a (θ _u , φ _v ) is based on the complex response of the virtual reception array when the reflected wave for the radar transmission signal arrives from the _{directional θ u} direction and the elevation angle direction φ _{v (Nt × Na).} ) The following column vector. The complex response a (θ _u , φ _v ) of the virtual reception array represents the phase difference calculated geometrically and optically by the element spacing between the antennas.

Further, θ _u is obtained by changing the directional range in which the arrival direction is estimated by a predetermined directional 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.

In addition, φ _v is the range of elevation angles for which the direction of arrival is estimated, which is changed by a _{predetermined elevation angle interval β 2.} For example, φ _v is set as follows.
φ _v ＝ φ min + vβ 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 arrangements VA # 1, ..., VA # (Nt × Na) described later. The elements of the direction vector of the virtual reception array represent the phase difference calculated geometrically and optically at the element spacing between the antennas in the order of the virtual reception array arrangement numbers VA # 1, ..., VA # (Nt × Na), which will be described later.

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

Further, the Doppler frequency information (fsΔΦ) may be converted into a relative velocity component and output. When converting the Doppler frequency fsΔΦ to 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 radio unit 107.

[Antenna arrangement in radar device 10]
The arrangement of the Nt transmitting antenna 106 and the Na receiving antenna 202 in the radar device 10 having the above configuration will be described.

FIG. 6 shows an antenna arrangement of a transmission 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 reception array composed of 3) and the antenna arrangement of the virtual reception array (number of elements: Nt × Na = 6) configured based on these transmission / reception array antennas are shown.

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

Further, the size (width) of the sub-array element is _{defined as D subarry,} and the desired antenna element spacing at which the grating lobe does not occur in the radar detection angle range is defined as De. In FIG. 6, the size D _{subarry of the} subarray element 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 1.5λ (1.5 wavelength), and the sub-array element spacing Dr of the receiving antenna is 1λ (1 wavelength). That is, the sub-array element spacings Dt and Dr are about one wavelength (λ) or more.

_{In the present embodiment, when the size D subarry of the sub-} array element is wider than the desired antenna element spacing De where the grating lobe does not occur 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 transmitting array antenna and the sub-array element spacing Dr of the receiving 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 a case where De = λ / 2, the sub-array element spacing of the transmitting array antenna is Dt = 1.5λ, and the sub-array element spacing of the receiving array antenna is Dr = λ.

In this case, as shown in FIG. 6, the element spacing near the center (other than the end) of the virtual reception array is the desired antenna element spacing De (= | Dt-Dr | = λ / 2). That is, in the virtual reception array, an array arrangement in which a grating lobe does not occur in the radar detection angle range can be obtained.

FIG. 7 shows a directivity pattern (Fourier beam pattern. Main beam: 0 ° direction) in the transmission / reception array antenna arrangement (in the case of De = 0.5λ, Dt = 1.5λ, Dr = λ) shown in FIG. As shown in FIG. 7, it can be seen that the grating lobe is not 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 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 the grating lobe. The transmitting antenna 106 and the receiving antenna 202 are arranged so as to be equal to the desired element spacing in which

By doing so, the element spacing of the virtual reception array configured according to the arrangement relationship of the transmitting antenna 106 and the receiving antenna 202 can be set to a desired element spacing at which the grating lobe does not occur. As a result, it is possible to eliminate the occurrence of erroneous detection due to the grating lobe when performing the direction estimation process in the direction estimation unit 214.

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

Note that FIG. 6 shows, as an example, a configuration in which the array antennas are linearly arranged in the horizontal direction in order to estimate the arrival direction in the horizontal direction. However, in the present embodiment, even when the array antennas are arranged in a straight line in the vertical direction in order to estimate the arrival direction in the vertical direction, similarly, a desired element spacing in which a grating lobe does not occur in the vertical direction is desired. Virtual reception array can be placed.

(Variation 1)
Variation 1 describes a case where the arrival direction is estimated in both the horizontal direction and the vertical direction.

The transmission array element or the reception array element is arranged in two dimensions in the vertical direction and the horizontal direction.

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

In FIG. 8, in the transmission array, each sub-array element is arranged in two dimensions, two in the horizontal direction and three in the vertical direction.

Further, in FIG. 8, the size of the sub-array element in the horizontal direction is set to D _subarry, and the size of the sub-array element in the vertical direction is set to De or less. That is, the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and less than or equal to 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 sub-array 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 horizontal sub-array element spacing of the receiving antenna is set to 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, 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 FIG. 8, in the horizontal direction, the element spacing near the center (other than the end) of the virtual reception array becomes the desired antenna element spacing De (= | Dt-Dr | = λ / 2). ..

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

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

When the direction estimation unit 214 estimates the arrival directions in the horizontal and vertical directions, the direction estimation evaluation function value P (θ _{u) is set by making the azimuth direction θ u} and the elevation angle direction φ _{v variable as shown in the following equation.} , Φ _v , k, fs, w), and let the azimuth direction and elevation angle direction at which the maximum value is obtained be the arrival direction 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 maximized.

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 beamformer method can be expressed as the following equation. Other methods such as Capon and MUSIC can be applied as well.

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

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

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

By using such an arrangement of the transmission / reception array antennas, it is possible to eliminate the occurrence of erroneous detection due to the grating lobe in both the horizontal direction and the vertical direction when the direction estimation process in the direction estimation unit 214 is performed.

Therefore, according to Variation 1, even when an array element having a sub-array configuration arranged in two dimensions is used, it is possible to suppress the generation of unnecessary grating lobes and realize a desired directivity pattern.

In FIG. 8, the case where the horizontal size of the sub-array element is D _subarry (> De) has been described, but the variation 1 is the case where the vertical size of the sub-array element is D _subarry (> De). Can be applied in the same way. In this case, in the vertical arrangement of the transmitting array, the difference (absolute value) between the element spacing of the transmitting array antenna and the element spacing of the receiving array antenna is equal to the desired element spacing in which the grating lobe does not occur. A transmission array may be placed.

(Variation 2)
Variation 2 describes another example of estimating the arrival direction in both the horizontal direction and the vertical direction.

Specifically, in the transmission array antenna, when the element spacing in the horizontal direction is Dt (> De) and the element spacing in the vertical direction is the desired antenna element spacing De, the transmitting array antennas are adjacent in the vertical direction. The two sub-array element arrangements arranged in a straight line in the horizontal direction are arranged in the horizontal direction with a distance equal to the desired antenna element distance De.

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

In FIG. 10, in the transmission array, each sub-array element is arranged in two dimensions, two in the horizontal direction and three in the vertical direction.

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

Similar to 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. Same as interval De. Further, as shown in FIG. 10, in the vertical direction, the element spacing of the transmitting array antenna is the same as the desired antenna element spacing De.

Further, in FIG. 10, the transmitting antennas 106 that are separated by the antenna element spacing De in the vertical direction of the transmitting array antennas (transmitting antennas 106 that are adjacent to each other in the vertical direction) are arranged at the same spacing as the antenna element spacing De in the horizontal direction. To. In other words, in the transmitting 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 interval as the desired element spacing.

For example, the arrangement of transmitting antennas Tx # 1 and Tx # 2 shown in FIG. 10 (that is, the arrangement of sub-array elements; the same applies hereinafter) and the arrangement of transmitting antennas T # 3 and Tx # 4 vertically adjacent to the arrangement are , It is arranged at the same interval as the antenna element interval De. Similarly, the arrangement of the transmitting antennas Tx # 3 and Tx # 4 and the arrangement of the transmitting antennas T # 5 and T # 6 vertically adjacent to the arrangement are laterally offset by the same distance as the antenna element spacing De. Have been placed.

In FIG. 10, in the horizontal direction, the element spacing near the center (other than the end) of the virtual reception array 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 is the desired antenna element spacing De, similar to the element spacing in the vertical direction of the transmission array. That is, in the virtual reception array, an array arrangement in which a grating lobe does not occur 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 arrangement of the array elements in the center (second stage) is compared with the arrangement of the array elements of the other array elements (first and third stages). Then, it is arranged with a De shift in the horizontal direction. As a result, in FIG. 10, the distance between the antenna elements in the two-dimensional plane in which the virtual reception array is arranged becomes closer as compared with the variation 1 (FIG. 8). This makes it possible to reduce the sidelobe level in the virtual reception array.

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

As shown in FIG. 11A, it can be seen that in the horizontal direction, no grating lobe is generated in an 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 lobe is generated is formed even in the vertical direction.

Further, as compared with Variation 1 (FIG. 9A), it can be seen that the sidelobe level is reduced in the horizontal directivity pattern, as shown in FIG. 11A.

By using such an arrangement of the transmission / reception 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 the direction estimation process in the direction estimation unit 214 is performed. it can.

Therefore, according to Variation 2, even when an array element having a sub-array configuration arranged in two dimensions is 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)
Variation 3 describes another example of estimating the arrival direction in both the horizontal direction and the vertical direction.

Specifically, in the transmitting array antenna, the spacing between the sub-array element arrays that are vertically adjacent and arranged in a straight line in the horizontal direction is the desired antenna element spacing De multiplied by the constant α, and is vertical. Two sub-array element arrays that are adjacent in the direction and arranged in a straight line in the horizontal direction are arranged at intervals that are obtained by multiplying the desired antenna element interval De by the constant β in the horizontal direction.

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

In FIG. 12, in the transmission array, each sub-array element is arranged in two dimensions, two in the horizontal direction and three in the vertical direction.

Further, in FIG. 12, the size of the sub-array element in the horizontal direction is set to D _subarry, and the size of the sub-array element in the vertical direction is set to De or less. That is, the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and less than or equal to the desired antenna element spacing De in the vertical direction.

FIG. 12 shows the desired antenna element spacing De = λ / 2, the horizontal sub-array element spacing Dt = 1.5λ of the transmitting array antenna, and the horizontal sub-array element spacing Dr = λ of the receiving array antenna, as in FIG. And. Further, the horizontal sub-array element spacing Dr = λ of the receiving array antenna.

Similar to 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 transmitting array antenna and the sub-array element spacing Dr of the receiving array antenna in the horizontal direction is , It 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 the spacing αDe obtained by multiplying the desired antenna element spacing De by the constant α.

Further, in FIG. 12, transmitting antennas 106 that are separated by element spacing αDe in the vertical direction of the transmitting array antennas (transmitting antennas 106 that are adjacent to each other in the vertical direction) multiply the desired antenna element spacing De by a constant β in the horizontal direction. The intervals βDe are offset. In other words, in the transmitting array antenna, two sub-array element arrays that are vertically adjacent to each other and arranged in a straight line in the horizontal direction are arranged in the horizontal direction with a spacing β times the desired element spacing.

For example, the arrangement of the transmitting antennas Tx # 1 and Tx # 2 shown in FIG. 12 and the arrangement of the transmitting antennas T # 3 and Tx # 4 vertically adjacent to the arrangement are arranged at intervals βDe. Similarly, the arrangement of the transmitting antennas Tx # 3 and Tx # 4 and the arrangement of the transmitting antennas T # 5 and T # 6 vertically adjacent to the arrangement are arranged with a horizontal interval βDe.

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

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

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

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

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

As a result, in FIG. 12, as in variation 2 (FIG. 10), the distance between the antenna elements in the two-dimensional plane on which the virtual reception array is arranged becomes closer as compared with variation 1 (FIG. 8). This makes it possible to reduce the sidelobe level in the virtual reception array.

Here, as shown in FIG. 12, in the vicinity of the center of the virtual reception array, the distance between the three adjacent antenna elements in the two-dimensional plane in which the virtual reception array is arranged is the desired antenna element distance De. In other words, the straight line connecting the three adjacent array elements in the two-dimensional plane in which the virtual reception array is arranged forms an equilateral triangle with one side as the antenna element spacing De. Since the equilateral triangle grating arrangement has higher grating lobe suppression performance than the square grating arrangement having the same opening length, the levels of the grating lobe and the side lobe can be further reduced as compared with the variation 2.

That is, the constants α and β are such that the element spacing between the three adjacent array elements in the vertical and horizontal directions is the desired antenna element spacing De (a regular triangle shape having one side as De). It may be set to.

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

Further, as compared with Variation 1 (FIG. 9A), it can be seen that the sidelobe 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) among the horizontal directivity patterns It can be seen that it has been reduced.

By using such an arrangement of the transmission / reception 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 process in the direction estimation unit 214. it can.

Therefore, according to the variation 3, even when an array element having a sub-array configuration arranged in two dimensions is 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 embodiment according to one aspect of the present disclosure has been described above.

It should be noted that the above-described embodiment and the operations related to each modification may be combined as appropriate.

Further, in the above embodiment, the case where the number of transmitting antennas 106 is Nt = 2 or 3 and the number of receiving antennas 202 is Na = 3 is illustrated. However, the number Nt of the transmitting antenna 106 and the number Na of the receiving antenna 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 composed of two antenna elements has been described, but the antenna elements constituting each of the transmitting antenna 106 and the receiving antenna 202 are 3. It may be composed of more than one element.

Further, in the variations 1 to 3 of the above-described embodiment, the case where the transmitting array antenna is arranged in two dimensions in the horizontal direction and the vertical direction and the receiving array antenna is arranged in one dimension in the horizontal direction has been described. However, in the present disclosure, the receiving array antenna may be arranged in two dimensions and the transmitting array antenna may be arranged in one dimension. In this case, the arrangement of the sub-array elements in the transmission array antenna described above may be applied to the arrangement of the sub-array elements in the reception array antenna.

Further, in the above embodiment, the case where the size of the antenna elements is larger than the desired antenna element spacing De in the horizontal direction and equal to or less than the desired antenna element spacing De in the vertical direction has been described. It may be larger 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, the horizontal direction and the vertical direction may be interchanged with respect to the arrangement of the sub-array elements in the above-mentioned transmission / reception array antenna.

Further, in the above embodiment, the case where the coded pulse radar is used has been described, but the present disclosure is also applicable to a radar method using a frequency-modulated pulse wave such as a chirp pulse radar.

Further, in the radar device 10 shown in FIG. 2, the radar transmitting unit 100 and the radar receiving unit 200 may be individually arranged at physically separated locations.

In the radar device, the radar transmitting unit transmits different transmission signals code-divided and multiplexed from a plurality of transmitting antennas, and the radar receiving unit separates each transmission signal for reception processing. The configuration of the radar device is not limited to this, and the radar transmitting unit transmits different transmission signals frequency-divided and multiplexed from a plurality of transmitting antennas, and the radar receiving unit separates each transmission signal for reception processing. It may be configured. Similarly, the radar device may be configured such that the radar transmitting unit transmits time-division-multiplexed transmission signals from a plurality of transmitting antennas and the radar receiving unit performs reception processing, as in the above embodiment. Effect 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) in which a control program is stored, and a working memory such as a RAM (Random Access Memory). .. In this case, the functions 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 such an 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 integrated into one chip, or may be integrated into one chip so as to include a part or all thereof.

<Summary of this disclosure>
The radar device of the present disclosure uses a radar transmitting unit that transmits a radar signal at a predetermined transmission cycle using a transmitting array antenna, and a receiving array antenna that receives a reflected wave signal in which the radar signal is reflected by a target. A radar receiving unit is provided, and 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 in the transmitting array antenna and the receiving array antenna. Arranged on a straight line of direction, each of the sub-array elements includes a plurality of antenna elements, the size of the sub-array elements is larger than the desired antenna element spacing in the first direction, and the sub-array elements of the transmitting array antenna. The absolute value of the difference between the interval and the sub-array element interval of the receiving array antenna is the same as the desired antenna element interval.

Further, in the radar device of the present disclosure, the desired antenna element spacing is 0.5 wavelength or more and 0.75 wavelength or less.

Further, in the radar device of the present disclosure, in either the transmission array antenna or the reception array antenna, the plurality of sub-array elements are further arranged in a second direction orthogonal to the first direction, and the said. When the size of the sub-array element is larger than the desired antenna element spacing in the first direction and equal to or less than the desired antenna element spacing in the second direction, the transmitting array antenna in the first direction 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 in the second direction, the sub-array element spacing is the desired antenna element. 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 so as to be shifted in the first direction by the same interval as the desired antenna element interval.

Further, in the radar device of the present disclosure, in either the transmission array antenna or the reception array antenna, the plurality of sub-array elements are further arranged in a second direction orthogonal to the first direction, and the said. When the size of the sub-array element is larger than the desired antenna element spacing in the first direction and equal to or less than the desired antenna element spacing in the second direction, the transmitting array antenna in the first direction 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 in the second direction, the sub-array element spacing is the desired antenna element spacing. The plurality of sub-array elements, which are ((√3) / 2) times as long as the above, and are arranged in the second direction, are (1/2) of the desired antenna element spacing in the first direction. The double intervals are shifted and placed.

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 modifications or modifications within the scope of the claims, which naturally belong to the technical scope of the present disclosure. Understood. Further, each component in the above embodiment (each variation) may be arbitrarily combined as long as the purpose of the disclosure is not deviated.

In each of the above embodiments, the present disclosure has been described for an example of configuring using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

Further, 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 embodiment and include an input and an output. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them. Although it is referred to as an LSI here, it may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

Further, the method of making an integrated circuit is not limited to LSI, and may be realized by using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection or setting of circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, the functional blocks may be integrated using that technology. There is a possibility of applying biotechnology.

The present disclosure is suitable as a radar device for detecting a wide-angle range.

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 Modulation unit 104 LPF
105 Transmission radio unit 106 Transmission antenna 111 Code storage unit 112 DA conversion unit 201 Antenna system processing unit 202 Reception antenna 203 Reception radio unit 204 Amplifier 205 Frequency converter 206 Orthogonal 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 (11)

With the transmitting array antenna
With the receiving array antenna,
A radar transmitter that transmits a radar signal using the transmission array antenna,
A radar receiving unit that receives the reflected wave signal reflected by the target by the radar signal using the receiving array antenna, and a radar receiving unit.
Equipped with
The transmitting array antenna includes a plurality of transmitting antennas and includes a plurality of transmitting antennas.
The receiving array antenna includes a plurality of receiving antennas and includes a plurality of receiving antennas.
The plurality of transmitting antennas are arranged linearly in the first direction.
The plurality of receiving antennas are arranged linearly in the first direction.
Each of the plurality of transmitting antennas includes a plurality of transmitting antenna elements arranged in a row in a second direction orthogonal to the first direction.
Each of the plurality of receiving antennas includes a plurality of receiving antenna elements arranged in a row in a second direction orthogonal to the first direction.
The transmitting antenna pitch of the transmitting 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 transmitting antenna pitch of the transmitting array antenna and the receiving antenna pitch of the receiving array antenna is 0.5 wavelength or more and 0.75 wavelength or less in the first direction.
Radar device. The transmitting array antenna and the receiving array antenna realize a virtual receiving array antenna having a plurality of virtual receiving antennas.
The virtual receiving antenna pitch of the virtual receiving array antenna includes those having a virtual receiving antenna pitch of 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 transmitting antenna pitch of the transmitting array antenna and the receiving antenna pitch of the receiving array antenna is 0.5 wavelength in the first direction.
The radar device according to claim 1. The transmitting array antenna and the receiving array antenna realize a virtual receiving array antenna having a plurality of virtual receiving antennas.
The virtual receiving antenna pitch of the virtual receiving array antenna is 0.5 wavelength in the first direction.
The radar device according to claim 3. The wavelength is determined by the frequency of the radar signal.
The radar device according to any one of claims 1 to 4. The first array antenna and
With the second array antenna,
A radar transmitter that transmits a radar signal using one of the first array antenna and the second array antenna, and a radar transmitter.
A radar receiving unit that receives a reflected wave signal in which the radar signal is 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.
The second array antenna includes a plurality of second antennas.
The plurality of first antennas are arranged linearly in the first direction.
The plurality of second antennas are arranged linearly in the first direction.
Each of the plurality of transmitting antennas includes a plurality of transmitting antenna elements arranged in a row in a second direction orthogonal to the first direction.
Each of the plurality of receiving antennas includes a plurality of receiving antenna elements arranged in a row in a second direction orthogonal to the first direction.
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.
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 below,
Radar device. The first array antenna and the second array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas.
The virtual receiving antenna pitch of the virtual receiving array antenna includes those having a virtual receiving antenna pitch of 0.5 wavelength or more and 0.75 wavelength or less in the first direction.
The radar device according to claim 6. 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 6. The first array antenna and the second array antenna realize a virtual reception array antenna having a plurality of virtual reception antennas.
The virtual receiving antenna pitch of the virtual receiving array antenna is 0.5 wavelength in the first direction.
The radar device according to claim 8. 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 6 to 9. The wavelength is determined by the frequency of the radar signal.
The radar device according to any one of claims 6 to 10.

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