JP7189034B2 - Direction-of-arrival estimation device and direction-of-arrival estimation method - Google Patents

Description

The present invention relates to technology for estimating the direction of arrival of radio waves.

A radar device emits radio waves and receives radio waves (reflected waves) reflected from a target, thereby estimating the direction of arrival of the reflected waves. The method of estimating the direction of arrival is a method of calculating the direction of arrival (angle) from information on the phase difference and amplitude difference of received signals obtained by a plurality of receiving antennas that receive reflected waves.

JP-A-2000-230974

In calculating the direction of arrival (angle), the distance between the receiving antennas is very important, and greatly affects the angular accuracy and phase folding. There is a trade-off relationship between angular accuracy and phase folding. Specifically, if the receiving antenna spacing is wide, the angle accuracy of the target is improved, but phase folding is likely to occur. gets worse.

In the radar device disclosed in Patent Document 1, the angle (azimuth) of the target detected by the radar device when the angles (azimuths) of the targets detected by two pairs of receiving antennas having different antenna intervals match each other is calculated. By adopting it as an angle, the angle accuracy of the target is improved while solving the problem of phase folding.

However, the radar device disclosed in Patent Document 1 cannot calculate directions of arrival (angles) for a plurality of targets having similar distances to the radar device and relative velocities to the radar device. .

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a direction-of-arrival estimation technique capable of improving the angular accuracy of each of a plurality of targets while solving the problem of phase folding.

A direction-of-arrival estimation apparatus according to the present invention includes a first angle of each of a plurality of targets derived from received signals obtained by a plurality of first receiving antennas arranged at a first interval, and the first an angle calculator for calculating a second angle of each of the plurality of targets derived from received signals obtained by a plurality of second receiving antennas arranged at a second interval wider than one interval; an estimating unit for estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the first angle, the plurality of second angles, and the phase folding angles of each of the plurality of second angles; wherein the estimating unit sets one of the second angle and the phase folding angle as the direction of arrival for each of the plurality of targets (first configuration).

In the direction-of-arrival estimation apparatus of the first configuration, a configuration in which a portion of the plurality of first reception antennas and a portion of the plurality of second reception antennas are common reception antennas (second configuration).

Another direction-of-arrival estimating apparatus according to the present invention is a receiving signal obtained by a first sub-array which is a combination of a plurality of receiving antennas, and a signal having the same shape as the first sub-array and the first sub-array. A first angle of each of a plurality of targets derived using a received signal obtained by a second subarray in which a first phase difference occurs between them, and a first angle having the same shape as the first subarray A fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the received signals obtained by the third sub-array and the third sub-array. an angle calculator that calculates a second angle of each of a plurality of targets derived using the received signals obtained in the above; a plurality of the first angles, a plurality of the second angles, and a plurality of the an estimating unit for estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the phase folding angles of the respective second angles, wherein the estimating unit estimates the direction of arrival of each of the plurality of targets, A configuration (third configuration) in which one of the second angle and the phase folding angle is set as the arrival direction.

In the direction-of-arrival estimation device having any one of the first to third configurations, the estimating unit includes a plurality of the first angles, a plurality of the second angles, and a phase folding angle for each of the plurality of the second angles. From the combination of , find one pair that minimizes the angular difference, and estimate the direction of arrival of the radio waves reflected from each of the plurality of targets based on the one pair (fourth configuration) good.

In the direction-of-arrival estimating apparatus having any one of the first to third configurations, the estimating unit adjusts the plurality of may be a configuration (fifth configuration) for estimating the direction of arrival of the radio waves reflected from each of the targets.

A direction-of-arrival estimation method according to the present invention includes: a first angle of each of a plurality of targets derived from received signals obtained by a plurality of first receiving antennas arranged at a first interval; an angle calculating step of calculating a second angle of each of the plurality of targets derived from received signals obtained by a plurality of second receiving antennas arranged at a second interval wider than one interval; an estimating step of estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the first angle of the plurality of second angles and the phase folding angles of each of the plurality of second angles; wherein in the estimating step, one of the second angle and the phase folding angle is set as the direction of arrival for each of the plurality of targets (sixth configuration).

Another direction-of-arrival estimation method according to the present invention is a method of estimating a received signal obtained by a first subarray that is a combination of a plurality of receiving antennas and the first subarray that has the same shape as the first subarray. A first angle of each of a plurality of targets derived using a received signal obtained by a second subarray in which a first phase difference occurs between them, and a first angle having the same shape as the first subarray A fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the received signals obtained by the third sub-array and the third sub-array. an angle calculation step of calculating a second angle of each of a plurality of targets derived using the received signals obtained in and a plurality of the first angles, the plurality of the second angles, and the plurality of the an estimating step of estimating directions of arrival of the radio waves reflected from each of the plurality of targets based on the phase folding angles of the respective second angles; One of the second angle and the phase folding angle is the arrival direction (seventh configuration).

According to the direction-of-arrival estimation technique according to the present invention, it is possible to improve the angular accuracy of each of a plurality of targets while solving the problem of phase folding.

A diagram showing a configuration example of a radar device The figure which shows the positional relationship of a radar installation and a target. The figure which shows the positional relationship of a radar installation and a target. Flowchart showing the flow of a first example of angle calculation processing and estimation processing Flowchart showing flow of second example of angle calculation processing and estimation processing Diagram showing an example of the arrangement of receiving antennas The figure which shows the other structural example of a radar apparatus

Exemplary embodiments of the invention are described in detail below with reference to the drawings.

<1. Configuration of Radar Device>
FIG. 1 is a diagram showing the configuration of a radar device 1 according to this embodiment. The radar device 1 is mounted on a vehicle such as an automobile. When the radar device 1 is mounted at the front end of the own vehicle, the radar device 1 acquires target object data related to a target existing in front of the own vehicle using transmission waves. The target data includes the distance to the target, the relative speed of the target with respect to the radar device 1, and the like. However, since the radar apparatus 1 according to this embodiment will be described as an example of a direction-of-arrival estimation apparatus, only the portion related to direction-of-arrival estimation will be described in the following description.

As shown in FIG. 1, the radar device 1 mainly includes a transmission section 2, reception sections 3n and 3w, and a signal processing device 4. As shown in FIG.

The receiving unit 3n includes a plurality of receiving antennas 31n. For example, the receiving unit 3n includes four receiving antennas 31n arranged along the lateral direction of the vehicle and corresponding to receiving channels ch1 to ch4, respectively. The receiving section 3w includes a plurality of receiving antennas 31w. For example, the receiver 3w includes four receiving antennas 31w arranged along the left-right direction of the vehicle and corresponding to the receiving channels ch5 to ch8.

The interval between adjacent receiving antennas 31n is a first interval d1, and in the receiving section 3w, the interval between adjacent receiving antennas 31w is a second interval d2 wider than the first interval d1. Note that the plurality of first intervals d1 may not be strictly the same as long as the plurality of first intervals d1 can be regarded as the same after considering design errors and variations. Preferably, the first interval d1 is less than half the wavelength of the received signal obtained by the receiving antenna 31n so that phase folding does not occur. However, even if phase folding occurs, it is possible to prevent phase folding within the FOV depending on the setting of the FOV of the radar device 1. Therefore, the first interval d1 is the received signal obtained by the receiving antenna 31n. may be greater than half the wavelength of In this embodiment, the first interval d1 is set to less than half the wavelength of the received signal obtained by the receiving antenna 31n. The plurality of second spacings d2 may not be strictly the same, as long as the plurality of second spacings d2 can be considered to be the same after considering design errors and variations. In this embodiment, the second spacing d2 is made larger than half the wavelength of the received signal obtained at the receiving antenna 31w.

As described above, in the receiving section 3n, the spacing between the adjacent receiving antennas 31n is the first spacing d1, and in the receiving section 3w, the spacing between the adjacent receiving antennas 31w is the second spacing d2 wider than the first spacing d1. However, the basic configuration of the receiving section 3n and the receiving section 3w is the same. Therefore, in the following description, the receiver 3n and the receiver 3w are appropriately described as the receiver 3 without distinguishing between them.

The transmitter 2 includes a signal generator 21 and a transmitter 22 . The transmitter 22 modulates the signal generated by the signal generator 21 to generate a transmission signal. The transmission antenna 23 converts a transmission signal into a transmission wave TW and outputs it.

The receiving section 3 includes a plurality of receiving antennas 31 and a plurality of individual receiving sections 32 connected to the plurality of receiving antennas 31 . In this embodiment, the receiving section 3 includes, for example, four receiving antennas 31 and four individual receiving sections 32 . The four individual receivers 32 correspond to the four receiving antennas 31, respectively. Each receiving antenna 31 receives a reflected wave RW from an object and acquires a received signal, and each individual receiving section 32 processes the received signal obtained by the corresponding receiving antenna 31 .

Each individual receiver 32 includes a mixer 33 and an A/D converter 34 . A received signal obtained by the receiving antenna 31 is sent to the mixer 33 after being amplified by a low-noise amplifier (not shown). A transmission signal from the transmitter 22 of the transmission unit 2 is input to the mixer 33 , and the transmission signal and the reception signal are mixed in the mixer 33 . As a result, a beat signal having a beat frequency that is the difference between the frequency of the transmission signal and the frequency of the reception signal is generated. The beat signal generated by the mixer 33 is converted to a digital signal by the A/D converter 34 and then output to the signal processing device 4 .

The signal processing device 4 includes a microcomputer including a CPU (Central Processing Unit), a memory 41, and the like. The signal processing device 4 stores various data to be operated on in the memory 41, which is a storage device. The memory 41 is, for example, a RAM (Random Access Memory). The signal processing device 4 includes a transmission control section 42, a Fourier transform section 43, and a data processing section 44 as functions realized by software on a microcomputer. The transmission controller 42 controls the signal generator 21 of the transmitter 2 . The data processor 44 includes a peak extractor 45 , an angle calculator 46 and an estimator 47 .

Since the receiving antenna 31 receives the reflected waves from a plurality of targets in a state in which they overlap each other, the Fourier transform unit 43 extracts the frequency components based on the reflected waves from each target from the beat signal generated based on the received signal. are separated (for example, FFT (Fast Fourier Transfer) processing). In FFT processing, reception level and phase information are calculated for each frequency point (sometimes referred to as frequency bin) set at predetermined frequency intervals.

The peak extraction unit 45 detects peaks from the results of FFT processing, etc., performed by the Fourier transform unit 43 .

The angle calculator 46 uses well-known azimuth calculation processing such as DBF and MUSIC to calculate the first angles of each of the plurality of targets derived from the reception signals obtained by the plurality of reception antennas 31n. The angle calculator 46 also calculates a second angle of each of the plurality of targets derived from the reception signals obtained by the plurality of reception antennas 31w using well-known azimuth calculation processing such as DBF and MUSIC.

A case in which two targets having similar distances to the radar device 1 and similar relative velocities to the radar device 1 are derived will be described below. The angle calculator 46 derives two targets _α1 and α2 shown in FIG. angle _θα2 is calculated.

The angle calculator 46 derives two targets _β1 and β2 shown in FIG. angle θ _β2 is calculated. At the second angles θ _β1 and θ _β2 , although the accuracy is high, phase folding occurs. Therefore, the original position of the target β1 may be the phase folding position β1′ or β1″ shown in FIG. The original position of may be the phase folding position β2' or β2'' shown in FIG. The number of phase folds is determined by the relationship between the second interval d2 and the wavelength of the received signal obtained by the receiving antenna 31w, and is not limited to the number in this embodiment. In the following description, θ _β1 ′ and θ _β1 ″ are used as the phase folding angles of the second angle θ _β1 , and θ _β2 ′ and θ _β2 ″ are used as the phase folding angles of the second angle θ _β2 . The phase fold angles θ _β1 ′, θ _β1 ″, θ _β2 ', and θ _β2 ″ are the respective angles of the phase fold positions β1′, β1″, β2′, and β1″.

_{The estimating unit 47 calculates 2 _ _} The direction of arrival of the radio waves reflected from each of the two targets is estimated. The estimating unit 47 can use the first angles θ _α1 and θ _α2 to resolve the phase folding problem of the targets β1 and β2, respectively.

Then, the estimating unit 47 sets one of the second angle θ _β1 and the phase folding angles θ _β1 ′ and θ _β1 ″ as the arrival direction of the radio wave reflected from the one target. For the other target, the estimator 47 determines one of the second angle θ _β2 and the phase folding angles θ _β2 ′ and θ _β2 ″ as the arrival direction of the radio wave reflected from the one target. Thereby, the angular accuracy of each of the plurality of targets can be improved.

The estimation unit 47 outputs the estimated azimuth (angle) at which the target exists to the memory 41, the vehicle control ECU 5, and the like.

<2. First Example of Angle Calculation Processing and Estimation Processing>
FIG. 4 is a flow chart showing a flow of a first example of calculation processing executed by the angle calculation unit 46 and estimation processing executed by the estimation unit 47. As shown in FIG.

The angle calculator 46 calculates first angles θ _α1 and θ _α2 (step S1). Next, the angle calculator 46 calculates second angles θ _β1 and θ _β2 (step S2). Steps S1 and S2 may be executed in a different order or in parallel.

After steps S1 and S2 are completed, either the angle calculator 46 or the estimator 47 calculates the phase folding angles θ _β1 ′, θ _β1 ″, θ _β2 ′, and θ _β2 ″ (step S3).

In step S4 following step S3, the estimator 47 calculates 12 angular differences. The 12 angular differences are the following (1) to (12). Each angle difference is an absolute value.
(1) Angle difference between first angle θ _α1 and phase folding angle θ _β1 ′ (2) Angle difference between first angle θ _α1 and phase folding angle θ _β2 ′ (3) First angle θ _α1 and Angle difference from second angle θ _β1 (4) Angle difference between first angle θ _α1 and second angle θ _β2 (5) Angle difference between first angle θ _α1 and phase folding angle θ _β1 ″ (6) Angle difference between first angle θ _α1 and phase folding angle θ _β2 ″ (7) Angle difference between first angle θ _α2 and phase folding angle θ _β1 ′ (8) First angle θ _α2 and Angle difference from the phase folding angle θ _β2 ' (9) Angle difference between the first angle θ _α2 and the second angle θ _β1 (10) Angle difference between the first angle θ _α2 and the second angle θ _β2 (11) Angle difference between first angle θ _α2 and phase folding angle θ _β1 ″ (12) Angle difference between first angle θ _α2 and phase folding angle θ _β2 ″

In step S5 following step S4, the estimating unit 47 finds (specifies) one pair with the smallest angle difference from among the 12 patterns, and converts the second angle or phase folding angle belonging to the specified pair to is the direction of arrival of the radio wave reflected from the target. In the following, the explanation will be continued taking as an example the case where one pair with the smallest angular difference is the above (1).

In step S6 following step S5, the estimator 47 calculates three angular differences for the other target. If the pair with the smallest angular difference is (1) above, the three angular differences in step S6 are (8), (10) and (12) above.

In step S7 following step S6, the estimating unit 47 finds (specifies) one pair having the smallest angle difference among the above three pairs, and calculates the second angle or phase folding angle belonging to the specified pair. , the direction of arrival of the radio waves reflected from the other target.

<3. Second Example of Angle Calculation Processing and Estimation Processing>
FIG. 5 is a flow chart showing a flow of a second example of calculation processing executed by the angle calculation unit 46 and estimation processing executed by the estimation unit 47. As shown in FIG. 5 that are the same as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

After completing step S3, the estimation unit 47 executes the process of step 8. FIG. The estimating unit 47 makes a first assumption that the target α1 and the target β1 are one of the targets, and the target α2 and the target β2 are the other target. ) and (5) to find (specify) one pair with the smallest angular difference, and from the above (8), (10), and (12), one pair with the smallest angular difference is found. Find (specify) and calculate the sum of the angular differences between the two specified pairs (step S8). Next, a second assumption is made that the targets α1 and β2 are one target, and the targets α2 and β1 are the other target, and the above (2), (4), Find (specify) one pair with the smallest angular difference from (6), find one pair with the smallest angular difference from the above (7), (9), and (11) ( specified), and the sum of the angular differences between the two specified pairs is calculated (step S9). It should be noted that steps S8 and S9 may be executed in a different order, or may be executed in parallel.

After steps S8 and S9 are completed, the estimating unit 47 adopts the first assumption when the sum calculated in step S8 is smaller than the sum calculated in step S9, and the sum calculated in step S9 is If it is smaller than the sum calculated in , the above second assumption is adopted (step S10). Then, when the above first assumption is adopted, the estimating unit 47 sets the arrival direction of the radio wave reflected from the target as the second angle or the phase folding angle belonging to the pair specified in step S8, and If assumption 2 is adopted, the direction of arrival of the radio wave reflected from the target is determined as the second angle or phase folding angle belonging to the pair specified in step S9 (step S10).

It cannot be generally said which of the above-described "first example of angle calculation processing and estimation processing" and "second example of angle calculation processing and estimation processing" is superior. For this reason, for example, it is sufficient to determine which one to adopt in consideration of the results of simulations or experiments in consideration of the assumed arrangement of a plurality of targets, the assumed specifications of the radar device 1, and the like.

<4. Others>
Various modifications can be made to the various technical features disclosed in this specification without departing from the gist of the technical creation in addition to the above-described embodiments. In addition, multiple embodiments and modifications shown in this specification may be implemented in combination to the extent possible.

In the above-described embodiment, the radar device 1 is configured to include the four receiving antennas 31n and the four receiving antennas 31w, but instead of the four receiving antennas 31n and the four receiving antennas 31w, for example, Six receiving antennas 31 may be provided. A reception channel ch11 shown in FIG. 6 is used instead of the reception channels ch1 and CH5 shown in FIG. 1, a reception channel ch12 shown in FIG. 6 is used instead of the reception channel ch2 shown in FIG. Receive channels ch14 to Ch16 shown in FIG. 6 are used instead of receive channels ch4, CH7 and CH8 shown in FIG. 1, respectively.

When the six receiving antennas 31 shown in FIG. 6 are provided, some of the plurality of receiving antennas having the first antenna spacing d1 and one of the plurality of receiving antennas having the second antenna spacing d2 are arranged. , and become a common receiving antenna. Therefore, when six receiving antennas 31 shown in FIG. 6 are provided, the number of receiving antennas 31 can be reduced, and accordingly the number of individual receiving units 32 can also be reduced.

Further, the radar device 1 described in the above-described embodiment is a radar device that solves the problem caused by the trade-off relationship between the angular accuracy and the phase folding according to the distance between the receiving antennas. Here, for example, when using azimuth calculation processing that calculates the angle from the phase difference between subarrays, such as ESPRIT and DoA-matrix, there is a problem caused by the trade-off relationship between the angle accuracy and phase folding according to the phase difference. need to be resolved. In terms of the trade-off relationship between the angle accuracy and phase folding according to the phase difference, if the amount of movement between the subarrays is large, the angle accuracy of the target is improved, but phase folding is likely to occur. If is small, phase folding is less likely to occur, but the angle accuracy of the target deteriorates.

Therefore, the radar device 1 shown in FIG. 1 may be changed to the configuration shown in FIG. 7, and the angle calculation section 46 may calculate the angle as follows. Other configurations and operations are basically the same as those of the above-described embodiment, so description thereof will be omitted.

The angle calculator 46 calculates the received signal obtained by the first subarray that is a combination of the 1ch receiving antenna 31 and the 2ch receiving antenna 31, and the second subarray that is a combination of the 2ch receiving antenna 31 and the 3ch receiving antenna 31. Two targets α1 and α2 shown in FIG. 2 are derived from the received signals obtained by the subarrays of , and the first angle θα1 of the target _α1 and the first angle θα2 of the target _α2 are calculated. .

The angle calculator 46 calculates the received signal obtained by the third sub-array, which is a combination of the 1ch receiving antenna 31 and the 2ch receiving antenna 31, and the fourth subarray, which is a combination of the 3ch receiving antenna 31 and the 4ch receiving antenna 31. Two targets β1 and β2 shown in FIG. 3 are derived from the received signals obtained by the subarrays of , and the second angle θ β1 of the target _β1 and the second angle θ _β2 of the target β2 are calculated. .

The radar device 1 shown in FIG. 7 can solve the problem caused by the trade-off relationship between the angle accuracy and the phase folding according to the phase difference. Therefore, it is possible to improve the angular accuracy of each of the plurality of targets while solving the problem of phase folding.

In the above-described embodiment, the vehicle-mounted radar system has been described, but the present invention can also be applied to an infrastructure radar system installed on a road or the like, an aircraft surveillance radar system, and the like.

Reference Signs List 1 radar device 2 transmitter 3 receiver 31, 31n, 31w receiving antenna 4 signal processor 46 angle calculator 47 estimator

Claims (7)

a first angle of each of a plurality of targets derived from received signals obtained by a plurality of first receiving antennas arranged at a first spacing, and at a second spacing wider than the first spacing; an angle calculator that calculates a second angle of each of the plurality of targets derived from received signals obtained by the plurality of arranged second receiving antennas;
An estimating unit for estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the plurality of first angles, the plurality of second angles, and the phase folding angles of each of the plurality of second angles. When,
with
The direction-of-arrival estimation device, wherein the estimating unit sets one of the second angle and the phase folding angle as the direction of arrival for each of the plurality of targets. 2. The direction-of-arrival estimation apparatus according to claim 1, wherein some of said plurality of first reception antennas and some of said plurality of second reception antennas are common reception antennas. A received signal obtained by a first subarray that is a combination of a plurality of receiving antennas, and a second subarray that has the same shape as the first subarray and produces a first phase difference between the first subarray and the first subarray. A first angle of each of a plurality of targets derived using a received signal obtained by a subarray, a received signal obtained by a third subarray having the same shape as the first subarray, and the and a received signal obtained by a fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the third sub-array and the third sub-array. an angle calculator that calculates a second angle of each of the plurality of targets;
An estimating unit for estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the plurality of first angles, the plurality of second angles, and the phase folding angles of each of the plurality of second angles. When,
with
The direction-of-arrival estimation device, wherein the estimating unit sets one of the second angle and the phase folding angle as the direction of arrival for each of the plurality of targets. The estimating unit finds one pair that minimizes the angle difference from a combination of the plurality of first angles, the plurality of second angles, and the phase folding angles of each of the plurality of second angles, The direction-of-arrival estimation apparatus according to any one of claims 1 to 3, which estimates directions of arrival of radio waves reflected from each of said plurality of targets based on said one pair. The estimating unit estimates the direction of arrival of the radio waves reflected from each of the plurality of targets so that a sum of angular differences between the first angle and the angle of the direction of arrival is minimized. A direction-of-arrival estimation device according to any one of 1 to 3. a first angle of each of a plurality of targets derived from received signals obtained by a plurality of first receiving antennas arranged at a first spacing, and at a second spacing wider than the first spacing; an angle calculation step of calculating a second angle of each of the plurality of targets derived from received signals obtained by a plurality of arranged second receiving antennas;
an estimation step of estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the plurality of first angles, the plurality of second angles, and the phase folding angles of each of the plurality of second angles; When,
with
The direction-of-arrival estimation method, wherein in the estimation step, one of the second angle and the phase folding angle is set as the direction of arrival for each of the plurality of targets. A received signal obtained by a first subarray that is a combination of a plurality of receiving antennas, and a second subarray that has the same shape as the first subarray and produces a first phase difference between the first subarray and the first subarray. A first angle of each of a plurality of targets derived using a received signal obtained by a subarray, a received signal obtained by a third subarray having the same shape as the first subarray, and the and a received signal obtained by a fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the third sub-array and the third sub-array. an angle calculation step of calculating a second angle of each of the plurality of targets;
an estimation step of estimating directions of arrival of radio waves reflected from each of the plurality of targets based on the plurality of first angles, the plurality of second angles, and the phase folding angles of each of the plurality of second angles; When,
with
The direction-of-arrival estimation method, wherein in the estimation step, one of the second angle and the phase folding angle is set as the direction of arrival for each of the plurality of targets.

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