Clutter suppression device, clutter suppression method, and target detection device

Abstract

The clutter suppression device (5) is configured to include a received signal acquisition unit (11) that acquires a received signal of a reflected wave, which is an electromagnetic wave reflected by a target, a convolution processing unit (12) that repeatedly convolves the received signal acquired by the received signal acquisition unit (11) with a distribution function while updating clutter parameters of the distribution function that indicates the distribution of clutter, and outputs multiple convolution results of the received signal and the distribution function, and a parameter search unit (13) that compares the multiple convolution results by the convolution processing unit (12) with each other and searches for clutter parameters corresponding to the clutter included in the received signal based on the comparison results of the multiple convolution results.The clutter suppression device (5) also includes a filter calculation unit (14) that calculates a filter for suppressing clutter included in the received signal using the clutter parameters searched for by the parameter search unit (13), and a clutter suppression unit (15) that suppresses clutter included in the received signal using the filter calculated by the filter calculation unit (14).

Description

[Technical Field]

[0001] The present disclosure relates to a clutter suppression device, a clutter suppression method, and a target detection device. [Background technology]

[0002] There is a clutter suppression device that suppresses clutter contained in a received signal. As such a clutter suppression device, for example, Non-Patent Document 1 discloses a clutter suppression device that calculates a filter for suppressing clutter contained in a received signal using a clutter parameter indicating the center frequency of the clutter and a clutter parameter indicating the frequency width of the clutter, and uses the filter to suppress the clutter contained in the received signal. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Ryuhei Takahashi, Kazufumi Hirata, Teruyuki Hara, and Atsushi Okamura Information Technology R&D Center, Mitsubishi Electric Corporation, Kamakura, Kanagawa, Japan “Coherent Integration with Null Constraint on Clutter Spectrum for Pulse Doppler Radar”, 2012 IEEE Summary of the Invention [Problem to be solved by the invention]

[0004] In the clutter suppression device disclosed in Non-Patent Document 1, the clutter parameters indicating the center frequency of the clutter and the clutter parameters indicating the frequency width of the clutter are not always set appropriately. For this reason, the clutter suppression device disclosed in Non-Patent Document 1 has a problem in that it may not be able to suppress the clutter contained in the received signal.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a clutter suppression device that can suppress clutter contained in a received signal. [Means for solving the problem]

[0006] A clutter suppression device according to the present disclosure includes a received signal acquisition unit that acquires a received signal of a reflected wave, which is an electromagnetic wave reflected by a target, a convolution processing unit that repeatedly convolves the received signal acquired by the received signal acquisition unit with the distribution function while updating clutter parameters of the distribution function that indicates the distribution of clutter, and outputs multiple convolution results of the received signal and the distribution function, and a parameter search unit that compares the multiple convolution results by the convolution processing unit with each other and searches for clutter parameters corresponding to the clutter included in the received signal based on the comparison results of the multiple convolution results. The clutter suppression device also includes a filter calculation unit that calculates a filter for suppressing the clutter included in the received signal using the clutter parameters searched for by the parameter search unit, and a clutter suppression unit that suppresses the clutter included in the received signal using the filter calculated by the filter calculation unit. and a threshold determination unit that determines a threshold to be used in CFAR (Constant False Alarm Rate) processing based on the clutter parameters searched for by the parameter search unit, where the threshold determination unit selects a threshold corresponding to the clutter parameter searched for by the parameter search unit from among thresholds to be used in CFAR processing that correspond to each of a plurality of clutter parameters and that result in a specified false alarm probability in CFAR processing. [Effects of the Invention]

[0007] According to the present disclosure, clutter contained in a received signal can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to a first embodiment. [Figure 2] 1 is a hardware configuration diagram showing hardware of a clutter suppression device 5 according to the first embodiment. [Figure 3] FIG. 10 is a hardware configuration diagram of a computer when the clutter suppression device 5 is realized by software, firmware, or the like. [Figure 4] 4 is a flowchart showing a clutter suppression method, which is a processing procedure of the clutter suppression device 5 according to the first embodiment. [Figure 5] FIG. 2 is an explanatory diagram showing the convolution result of the Doppler spectrum of the received signal x and a filter with appropriate clutter parameters. [Figure 6] FIG. 10 is an explanatory diagram showing the convolution result of the Doppler spectrum of the received signal x and a filter with an inappropriate clutter parameter. [Figure 7] FIG. 7A is an explanatory diagram showing a range-Doppler map of clutter when multiple clutters are included in the received signal x, FIG. 7B is an explanatory diagram showing an example of clutter simulated as a collection of multiple point wave sources, and FIG. 7C is an explanatory diagram showing an example of a spectrum of clutter having clutter parameters searched for by the parameter search unit 13. [Figure 8] FIG. 10 is an explanatory diagram showing the eigenvalue number K when the cumulative sum of eigenvalues ​​exceeds a certain value. [Figure 9] FIG. 10 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to a second embodiment. [Figure 10] FIG. 10 is a hardware configuration diagram showing hardware of a clutter suppression device 5 according to a second embodiment. [Figure 11] 1 is an explanatory diagram showing an example in which the Doppler spectrum shape of a received signal x has sparse and dense portions. FIG. [Figure 12] FIG. 10 is an explanatory diagram showing an example of eliminating the density variation in the Doppler spectrum shape. [Figure 13] FIG. 10 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to a third embodiment. [Figure 14] FIG. 10 is a hardware configuration diagram showing hardware of a clutter suppression device 5 according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1 FIG. 1 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to the first embodiment. FIG. 2 is a hardware configuration diagram showing the hardware of the clutter suppression device 5 according to the first embodiment. The target detection device shown in FIG. 1 includes a transmitter 1, a transmitting antenna 2, a receiving antenna 3, a receiver 4, a clutter suppression device 5, a detector 6, and a tracker .

[0011] The transmitter 1 generates a transmission signal and outputs the transmission signal to the transmission antenna 2 . The transmitting antenna 2 radiates the transmission signal output from the transmitter 1 into space as an electromagnetic wave. The receiving antenna 3 receives reflected waves, which are electromagnetic waves that are reflected by a target after being radiated into space from the transmitting antenna 2, and outputs a received signal of the reflected waves to the receiver 4. The receiver 4 performs various signal processing on the received signal output from the receiving antenna 3, and outputs the processed received signal to the clutter suppression device 5. The various types of signal processing include, for example, demodulating the received signal, amplifying the received signal, converting the received signal from an analog signal to a digital signal, pulse compressing the received signal, and integrating the received signal.

[0012] The clutter suppression device 5 includes a received signal acquisition unit 11, a convolution processing unit 12, a parameter search unit 13, a filter calculation unit 14, and a clutter suppression unit 15. The clutter suppression device 5 suppresses clutter contained in the received signal output from the receiver 4 and outputs the clutter-suppressed received signal to the detector 6.

[0013] The detector 6 acquires the clutter-suppressed received signal from the clutter suppression device 5 . The detector 6 detects a target based on the received signal after clutter suppression. The detector 6 outputs the target detection result to the tracker 7 . The tracker 7 acquires the target detection result from the detector 6 . The tracker 7 performs a process of tracking the target based on the detection result of the target.

[0014] The received signal acquisition unit 11 is realized by, for example, a received signal acquisition circuit 21 shown in FIG. The received signal acquisition unit 11 acquires the received signal from the receiver 4 . The received signal acquisition unit 11 outputs the received signal to the convolution processing unit 12 and the clutter suppression unit 15, respectively.

[0015] The convolution processing unit 12 is realized by, for example, a convolution processing circuit 22 shown in FIG. The convolution processing unit 12 acquires the received signal from the received signal acquisition unit 11 . The convolution processing unit 12 repeatedly performs convolution of the received signal with the distribution function while updating the clutter parameters of the distribution function that indicates the distribution of the clutter, and outputs multiple convolution results of the received signal with the distribution function to the parameter search unit 13.

[0016] The parameter search unit 13 is realized by, for example, a parameter search circuit 23 shown in FIG. The parameter search unit 13 acquires a plurality of convolution results from the convolution processing unit 12 . The parameter search unit 13 compares the multiple convolution results with each other. The parameter search unit 13 searches for clutter parameters corresponding to the clutter contained in the received signal based on the comparison result of the multiple convolution results. The clutter parameters of the distribution function are a parameter indicating the center frequency of the clutter and a parameter indicating the frequency width of the clutter. The parameter search unit 13 outputs the clutter parameters corresponding to the clutter to the filter calculation unit 14 .

[0017] The filter calculation unit 14 is realized by, for example, a filter calculation circuit 24 shown in FIG. The filter calculation unit 14 acquires clutter parameters corresponding to the clutter from the parameter search unit 13. The filter calculation unit 14 uses the clutter parameters to calculate a clutter suppression filter, which is a filter for suppressing clutter contained in the received signal. The clutter suppression filter is, for example, a Gaussian filter. The filter calculation unit 14 outputs the clutter suppression filter to the clutter suppression unit 15 .

[0018] The clutter suppression unit 15 is realized by, for example, a clutter suppression circuit 25 shown in FIG. The clutter suppression unit 15 acquires the received signal from the received signal acquisition unit 11 and acquires the clutter suppression filter from the filter calculation unit 14 . The clutter suppressor 15 uses a clutter suppression filter to suppress clutter contained in the received signal. The clutter suppressor 15 outputs the clutter-suppressed received signal to the detector 6 .

[0019] 1, it is assumed that each of the components of the clutter suppression device 5, namely, the received signal acquisition section 11, the convolution processing section 12, the parameter search section 13, the filter calculation section 14, and the clutter suppression section 15, is realized by dedicated hardware as shown in Fig. 2. In other words, it is assumed that the clutter suppression device 5 is realized by a received signal acquisition circuit 21, a convolution processing circuit 22, a parameter search circuit 23, a filter calculation circuit 24, and a clutter suppression circuit 25. Each of the received signal acquisition circuit 21, the convolution processing circuit 22, the parameter search circuit 23, the filter calculation circuit 24, and the clutter suppression circuit 25 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0020] The components of the clutter suppression device 5 are not limited to those realized by dedicated hardware, and the clutter suppression device 5 may be realized by software, firmware, or a combination of software and firmware. The software or firmware is stored as a program in the memory of a computer. A computer refers to hardware that executes the program, such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor).

[0021] FIG. 3 is a hardware configuration diagram of a computer when the clutter suppression device 5 is realized by software, firmware, or the like. When the clutter suppression device 5 is realized by software, firmware, or the like, a program for causing a computer to execute the respective processing procedures of the received signal acquisition unit 11, the convolution processing unit 12, the parameter search unit 13, the filter calculation unit 14, and the clutter suppression unit 15 is stored in the memory 31. Then, a processor 32 of the computer executes the program stored in the memory 31.

[0022] 2 shows an example in which each of the components of the clutter suppression device 5 is realized by dedicated hardware, while Fig. 3 shows an example in which the clutter suppression device 5 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the clutter suppression device 5 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0023] Next, the operation of the target detection device shown in FIG. 1 will be described. FIG. 4 is a flowchart showing a clutter suppression method, which is a processing procedure of the clutter suppression device 5 according to the first embodiment.

[0024] The transmitter 1 generates a transmission signal and outputs the transmission signal to the transmission antenna 2 . When the transmitting antenna 2 receives a transmission signal from the transmitter 1, it radiates the transmission signal into space as an electromagnetic wave. The electromagnetic waves emitted into space are reflected by a target. The reflected waves, which are the electromagnetic waves reflected by the target, are received by the receiving antenna 3. When the receiving antenna 3 receives the reflected waves, it outputs a received signal of the reflected waves to the receiver 4. When the receiver 4 receives a received signal from the receiving antenna 3, it performs various signal processing on the received signal and outputs the processed received signal x to the clutter suppression device 5.

[0025] The received signal acquisition unit 11 of the clutter suppression device 5 acquires the received signal x from the receiver 4 (step ST1 in FIG. 4). The received signal acquisition unit 11 outputs the received signal x to the convolution processing unit 12 and the clutter suppression unit 15, respectively.

[0026] The convolution processing unit 12 acquires the received signal x from the received signal acquisition unit 11 . The convolution processing unit 12 calculates a distribution function h(f c ,σ d ) clutter parameter f c ,σ dWhile updating the received signal x and distribution function h(f c ,σ d ) is repeatedly convolved with (step ST2 in FIG. 4). f c denotes the central frequency of the clutter, and σ d indicates the frequency width of the clutter. Clutter central frequency f c For example, there are 10 possible frequencies, and the frequency width of the clutter is σ d If the number of assumed frequency bands is, for example, five, the convolution processing unit 12 generates (10×5) distribution functions h(f c ,σ d ) is convolved with the received signal x.

[0027] TIFF0007814649000001.tif60166

[0028] The convolution processing unit 12 calculates the received signal x and the distribution function h(f c ,σ d ) and outputs the results of convolution with the parameter search unit 13. Distribution function h(f c ,σ d ) clutter parameter, the central frequency f c and the clutter frequency width σ d If the values ​​of are appropriate, the received signal x and the distribution function h(f c ,σ d ) results in a spectrum with a large amplitude, as shown in FIG. FIG. 5 is an explanatory diagram showing the convolution result of the Doppler spectrum of the received signal x and a filter with appropriate clutter parameters. Figure 5 shows the shape of the Doppler frequency domain in a filter with appropriate clutter parameters. In a filter with appropriate clutter parameters, the central frequency f of the clutter, which is the clutter parameter of the filter, is c is the center frequency f of the clutter contained in the received signal x.c and the clutter frequency width σ of the clutter, which is a clutter parameter of the filter, d is the frequency width σ of the clutter contained in the received signal x. d It matches.

[0029] Distribution function h(f c ,σ d ) clutter parameter, the central frequency f c or clutter frequency width σ d If any of the values ​​is inappropriate, the received signal x and the distribution function h(f c ,σ d ) results in a spectrum with a small amplitude, as shown in FIG. FIG. 6 is an explanatory diagram showing the convolution result of the Doppler spectrum of the received signal x and a filter with an inappropriate clutter parameter. Figure 6 shows the shape of the Doppler frequency domain in a filter with inappropriate clutter parameters. In a filter with inappropriate clutter parameters, the central frequency f of the clutter, which is the clutter parameter of the filter, c is the center frequency f of the clutter contained in the received signal x. c or the frequency width σ of the clutter, which is a clutter parameter of the filter. d is the frequency width σ of the clutter contained in the received signal x. d is inconsistent with

[0030] The parameter search unit 13 acquires a plurality of convolution results from the convolution processing unit 12 . The parameter search unit 13 compares the multiple convolution results with each other. The parameter search unit 13 searches for a clutter parameter f corresponding to the clutter included in the received signal x based on a comparison result of the plurality of convolution results. c ,σ d (Step ST3 in FIG. 4). Specifically, the parameter search unit 13 selects f corresponding to the maximum convolution result among the multiple convolution results as shown in the following equation (4): c ,σ d Explore. Here, the parameter search unit 13 selects f corresponding to the maximum convolution result among the multiple convolution results. c ,σ d However, this is merely an example, and the parameter search unit 13 may search for, for example, f corresponding to the second largest convolution result within a practically acceptable range. c ,σ d Alternatively, we can search for f corresponding to the third largest convolution result. c ,σ d It is also possible to search for: The parameter search unit 13 searches for a clutter parameter f c ,σ d is output to the filter calculation unit 14.

[0031] TIFF0007814649000002.tif13166

[0032] 7A is an explanatory diagram showing a range-Doppler map of clutter when multiple clutters are included in the received signal x. The spread of the clutter in the range-Doppler direction has a Gaussian distribution. The clutter shown in FIG. 7A can be simulated as a collection of multiple point wave sources, as shown in FIG. 7B. FIG. 7B is an explanatory diagram showing an example of clutter simulated as a collection of multiple point wave sources. FIG. 7C is an explanatory diagram showing an example of the spectrum of clutter having clutter parameters searched for by the parameter search unit 13. As shown in FIG.

[0033] The filter calculation unit 14 receives from the parameter search unit 13 the clutter parameter f corresponding to the clutter. c ,σ d Get. The filter calculation unit 14 calculates the clutter parameter f c ,σ d is used to generate a clutter suppression filter w NCCI (f) is calculated (step ST4 in FIG. 4). The filter calculation unit 14 calculates the clutter suppression filter w NCCI (f) is output to the clutter suppression unit 15.

[0034] Hereinafter, the clutter suppression filter w NCCI The calculation process of (f) will be specifically explained. The filter calculation unit 14 calculates the clutter parameter f as shown in the following equation (5). c ,σ d Using this, the clutter correlation matrix R cc Calculate.

[0035] TIFF0007814649000003.tif65166In equation (6), Δt is the PRI (Pulse Repetition Interval) and M is the number of FFT (Fast Fourier Transformation) points.

[0036] The filter calculation unit 14 calculates the clutter correlation matrix R as shown in the following equation (9): cc is expanded into eigenvalues, and the eigenvectors corresponding to the eigenvalues ​​are E s Let's say.

[0037] TIFF0007814649000004.tif27166

[0038] The eigenvector is E=[e1,e2,...,e M ], as shown in Figure 8, if the eigenvalue number when the cumulative sum of the eigenvalues ​​exceeds a certain value is K, then the eigenvector E corresponding to the eigenvalue s is E s =[e1,e2, ,e K ]. FIG. 8 is an explanatory diagram showing the eigenvalue number K when the cumulative sum of the eigenvalues ​​exceeds a certain value.

[0039] The filter calculation unit 14 calculates the eigenvector E s Calculate P·a(f) using The filter calculation unit 14 calculates the clutter suppression filter w using P·a(f) as shown in the following equation (11): NCCI Calculate (f).

[0040] TIFF0007814649000005.tif32166In equations (10) and (11), I is an identity matrix, and f is a frequency corresponding to the Doppler bin of interest.

[0041] The clutter suppression unit 15 acquires the received signal x from the received signal acquisition unit 11 and calculates the clutter suppression filter w from the filter calculation unit 14. NCCI Obtain (f). The clutter suppression unit 15 includes a clutter suppression filter w NCCI (f) is used to suppress clutter contained in the received signal x (step ST5 in FIG. 4). That is, the clutter suppression unit 15 uses a clutter suppression filter w NCCI (f) and the received signal x are substituted into the following equation (12) to obtain the received signal P after clutter suppression. NCCI Calculate (f). The clutter suppressor 15 receives the clutter-suppressed received signal P NCCI (f) is output to detector 6.

[0042] TIFF0007814649000006.tif12166

[0043] The detector 6 receives the clutter-suppressed received signal P from the clutter suppressor 15. NCCI Obtain (f). The detector 6 detects, for example, the received signal P after clutter suppression. NCCIThe target is detected by performing CFAR (Constant False Alarm Rate) processing on (f). The received signal P after clutter suppression by the clutter suppressor 15 NCCI (f) is a received signal from which clutter has been removed, improving the accuracy with which the detector 6 detects targets. The detector 6 outputs the target detection result to the tracker 7 .

[0044] The tracker 7 acquires the target detection result from the detector 6 . The tracker 7 performs a process of tracking the target based on the detection result of the target.

[0045] In the first embodiment described above, the clutter suppression device 5 is configured to include a received signal acquisition unit 11 that acquires a received signal of a reflected wave, which is an electromagnetic wave reflected by a target; a convolution processing unit 12 that repeatedly convolves the received signal acquired by the received signal acquisition unit 11 with a distribution function while updating clutter parameters of the distribution function that indicates the distribution of clutter, and outputs multiple convolution results of the received signal and the distribution function; and a parameter search unit 13 that compares the multiple convolution results by the convolution processing unit 12 with each other and searches for clutter parameters corresponding to the clutter included in the received signal based on the comparison results of the multiple convolution results. The clutter suppression device 5 also includes a filter calculation unit 14 that calculates a filter for suppressing clutter included in the received signal using the clutter parameters searched for by the parameter search unit 13, and a clutter suppression unit 15 that suppresses clutter included in the received signal using the filter calculated by the filter calculation unit 14. Therefore, the clutter suppression device 5 can suppress clutter included in the received signal.

[0046] Embodiment 2 In the second embodiment, a clutter suppression device 5 will be described in which the convolution processing unit 16 convolves the received signal acquired by the received signal acquisition unit 11 with a distribution function, and then further convolves the distribution function with the result of the convolution of the received signal with the distribution function.

[0047] Fig. 9 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to embodiment 2. In Fig. 9, the same reference numerals as in Fig. 1 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 10 is a hardware configuration diagram showing the hardware of the clutter suppression device 5 according to embodiment 2. In Fig. 10, the same reference numerals as in Fig. 2 indicate the same or corresponding parts, and detailed description thereof will be omitted. The target detection device shown in FIG. 9 includes a transmitter 1, a transmitting antenna 2, a receiving antenna 3, a receiver 4, a clutter suppression device 5, a detector 6, and a tracker . The clutter suppression device 5 shown in FIG. 9 includes a received signal acquisition unit 11, a convolution processing unit 16, a parameter search unit 13, a filter calculation unit 14, and a clutter suppression unit 15.

[0048] The convolution processing unit 16 is realized by, for example, a convolution processing circuit 26 shown in FIG. The convolution processing unit 16 acquires the received signal from the received signal acquisition unit 11 . Similar to the convolution processing unit 12 shown in FIG. 1, the convolution processing unit 16 repeatedly performs convolution of the received signal with the distribution function, while updating the clutter parameters of the distribution function that indicates the distribution of the clutter. The convolution processing unit 16 repeatedly performs convolution of the received signal with the distribution function, and then further performs convolution of the distribution function with each of the results of convolution of the received signal with the distribution function. The convolution processing unit 16 outputs the convolution results of the distribution function for each convolution result to the parameter searching unit 13.

[0049] 9, it is assumed that the components of the clutter suppression device 5, namely, the received signal acquisition unit 11, the convolution processing unit 16, the parameter search unit 13, the filter calculation unit 14, and the clutter suppression unit 15, are each realized by dedicated hardware as shown in Fig. 10. In other words, it is assumed that the clutter suppression device 5 is realized by a received signal acquisition circuit 21, a convolution processing circuit 26, a parameter search circuit 23, a filter calculation circuit 24, and a clutter suppression circuit 25. Each of the received signal acquisition circuit 21, the convolution processing circuit 26, the parameter search circuit 23, the filter calculation circuit 24, and the clutter suppression circuit 25 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0050] The components of the clutter suppression device 5 are not limited to those realized by dedicated hardware, and the clutter suppression device 5 may be realized by software, firmware, or a combination of software and firmware. When the clutter suppression device 5 is realized by software, firmware, or the like, a program for causing a computer to execute the processing procedures of the received signal acquisition unit 11, the convolution processing unit 16, the parameter search unit 13, the filter calculation unit 14, and the clutter suppression unit 15 is stored in a memory 31 shown in Fig. 3. Then, a processor 32 shown in Fig. 3 executes the program stored in the memory 31.

[0051] 9 shows an example in which each of the components of the clutter suppression device 5 is realized by dedicated hardware, while Fig. 3 shows an example in which the clutter suppression device 5 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the clutter suppression device 5 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0052] Next, the operation of the target detection device shown in Fig. 9 will be described. However, apart from the convolution processing unit 16, the target detection device is the same as that shown in Fig. 1. Therefore, only the operation of the convolution processing unit 16 will be described here.

[0053] In the target detection device shown in FIG. 1, when the Doppler spectrum shape of the received signal x has density as shown in FIG. 11, the parameter search unit 13 calculates the clutter frequency width σ d The search accuracy may be degraded. FIG. 11 is an explanatory diagram showing an example in which the Doppler spectrum shape of the received signal x has sparse and dense portions. In the example of FIG. 11, the Doppler spectrum has some distant parts, so the estimated Doppler spectrum shape differs from the true Doppler spectrum shape. In the target detection device shown in FIG. 9, even if there are sparse or dense Doppler spectrum shapes of the received signal x, the parameter search unit 13 can find the clutter frequency width σ d In order to prevent the deterioration of the search accuracy, a convolution processing unit 16 is provided.

[0054] The convolution processing unit 16 acquires the received signal x from the received signal acquisition unit 11 . The convolution processing unit 16, like the convolution processing unit 12 shown in FIG. 1, calculates a distribution function h(f c ,σ d ) clutter parameter f c ,σ d While updating the received signal x and distribution function h(f c ,σ d ) and convolution with As shown in FIG. 12, the convolution processing unit 16 calculates the received signal x and the distribution function h(f c ,σ d ) is repeatedly convolved with the received signal x and the distribution function h(f c ,σ d ) and each convolution result, the distribution function h(f c ,σ d) convolution is performed. The convolution processing unit 16 calculates the received signal x and the distribution function h(f c ,σ d ) and the distribution function h(f c ,σ d ) is output to the parameter search unit 13.

[0055] TIFF0007814649000007.tif10166

[0056] FIG. 12 is an explanatory diagram showing an example of eliminating the density variation in the Doppler spectrum shape. In the example of Figure 12, the received signal x and the distribution function h(f c ,σ d ) and each convolution result, the distribution function h(f c ,σ d ) is convoluted to eliminate the distant parts of the Doppler spectrum. As a result, the estimated Doppler spectrum shape is roughly the same as the true Doppler spectrum shape.

[0057] In the second embodiment described above, the clutter suppression device 5 is configured so that the convolution processing unit 16 repeatedly convolves the received signal acquired by the received signal acquisition unit 11 with a distribution function, and then further convolves the distribution function with each of the convolution results of the received signal and the distribution function, and outputs the convolution result of each of the convolution results with the distribution function. Therefore, even if the Doppler spectrum shape of the received signal varies in density, the clutter contained in the received signal can be suppressed.

[0058] Embodiment 3 In the third embodiment, a clutter suppression device 5 including a threshold value determination unit 17 that determines a threshold value to be used in CFAR processing based on the clutter parameters searched for by the parameter search unit 13 will be described.

[0059] Fig. 13 is a configuration diagram showing a target detection device including a clutter suppression device 5 according to embodiment 3. In Fig. 13, the same reference numerals as in Figs. 1 and 9 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 14 is a hardware configuration diagram showing the hardware of the clutter suppression device 5 according to embodiment 3. In Fig. 14, the same reference numerals as in Fig. 2 and Fig. 10 indicate the same or corresponding parts, and detailed description thereof will be omitted. The target detection device shown in FIG. 13 includes a transmitter 1, a transmitting antenna 2, a receiving antenna 3, a receiver 4, a clutter suppression device 5, a detector 6, and a tracker . The clutter suppression device 5 shown in FIG. 13 includes a received signal acquisition unit 11, a convolution processing unit 12, a parameter search unit 13, a filter calculation unit 14, a clutter suppression unit 15, and a threshold determination unit 17.

[0060] The threshold value determining unit 17 is realized by, for example, a threshold value determining circuit 27 shown in FIG. The threshold determination unit 17 acquires the clutter parameters from the parameter search unit 13 . The threshold value determination unit 17 determines a threshold value to be used in the CFAR processing based on the clutter parameters searched for by the parameter search unit 13 . The threshold value determination unit 17 outputs the threshold value used in the CFAR processing to the detector 6 .

[0061] In the target detection device shown in Fig. 13, the threshold value determination unit 17 is applied to the target detection device shown in Fig. 1. However, this is merely an example, and the threshold value determination unit 17 may also be applied to the target detection device shown in Fig. 9.

[0062] 13, it is assumed that the components of the clutter suppression device 5, namely, the received signal acquisition section 11, the convolution processing section 12, the parameter search section 13, the filter calculation section 14, the clutter suppression section 15, and the threshold determination section 17, are each realized by dedicated hardware as shown in Fig. 14. In other words, it is assumed that the clutter suppression device 5 is realized by a received signal acquisition circuit 21, a convolution processing circuit 22, a parameter search circuit 23, a filter calculation circuit 24, a clutter suppression circuit 25, and a threshold determination circuit 27. Each of the received signal acquisition circuit 21, the convolution processing circuit 22, the parameter search circuit 23, the filter calculation circuit 24, the clutter suppression circuit 25, and the threshold determination circuit 27 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0063] The components of the clutter suppression device 5 are not limited to those realized by dedicated hardware, and the clutter suppression device 5 may be realized by software, firmware, or a combination of software and firmware. When the clutter suppression device 5 is realized by software, firmware, or the like, a program for causing a computer to execute the processing procedures of the received signal acquisition unit 11, the convolution processing unit 12, the parameter search unit 13, the filter calculation unit 14, the clutter suppression unit 15, and the threshold determination unit 17 is stored in a memory 31 shown in Fig. 3. Then, a processor 32 shown in Fig. 3 executes the program stored in the memory 31.

[0064] 14 shows an example in which each of the components of the clutter suppression device 5 is realized by dedicated hardware, while Fig. 3 shows an example in which the clutter suppression device 5 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the clutter suppression device 5 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0065] Next, the operation of the target detection device shown in Fig. 13 will be described. However, apart from the threshold value determination unit 17, the target detection device is the same as that shown in Fig. 1. Therefore, the operation of the threshold value determination unit 17 will mainly be described here.

[0066] The internal memory of the threshold value determination unit 17 or a storage device (not shown) stores a plurality of clutter center frequencies f c and the frequency width of multiple clutters σ d For each combination of the above, a CFAR threshold value, which is a threshold value used in CFAR processing, is stored. The threshold value corresponding to each combination is, for example, a threshold value that results in a specified false alarm probability in CFAR processing when a clutter-suppressed Doppler spectrum in which a target is superimposed on an arbitrary cell is generated by Monte Carlo simulation.

[0067] The threshold determination unit 17 receives the clutter parameter, which is the central frequency f c and the clutter frequency width σ d and get. The threshold value determination unit 17 determines the central frequency f of the clutter from its internal memory or the like. c and the clutter frequency width σ d The CFAR threshold corresponding to each of the above is acquired, and the CFAR threshold is determined as the threshold to be used in the CFAR processing. The threshold determination unit 17 outputs the CFAR threshold to the detector 6 .

[0068] The detector 6 receives the clutter-suppressed received signal P from the clutter suppressor 15. NCCI (f) is acquired, and the CFAR threshold is acquired from the threshold determination unit 17. The detector 6 uses the CFAR threshold to detect the received signal P after clutter suppression. NCCI The target is detected by performing CFAR processing on (f). The detector 6 outputs the target detection result to the tracker 7 .

[0069] In the above-described third embodiment, the clutter suppression device 5 is configured to include the threshold determination unit 17 that determines the threshold to be used in CFAR processing based on the clutter parameters searched for by the parameter search unit 13. Therefore, the accuracy of target detection by the detector 6 can be improved compared to when the detector 6 uses an arbitrary threshold.

[0070] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments. [Industrial Applicability]

[0071] The present disclosure is suitable for a clutter suppression device, a clutter suppression method, and a target detection device. [Explanation of symbols]

[0072] 1 transmitter, 2 transmitting antenna, 3 receiving antenna, 4 receiver, 5 clutter suppression device, 6 detector, 7 tracker, 11 received signal acquisition unit, 12 convolution processing unit, 13 parameter search unit, 14 filter calculation unit, 15 clutter suppression unit, 16 convolution processing unit, 17 threshold determination unit, 21 received signal acquisition circuit, 22 convolution processing circuit, 23 parameter search circuit, 24 filter calculation circuit, 25 clutter suppression circuit, 26 convolution processing circuit, 27 threshold determination circuit, 31 memory, 32 processor.

Claims

1. a received signal acquisition unit that acquires a received signal of a reflected wave, which is an electromagnetic wave reflected by a target; a convolution processing unit that repeatedly convolves the received signal acquired by the received signal acquisition unit with the distribution function indicating a clutter distribution while updating clutter parameters of the distribution function, and outputs a plurality of convolution results of the received signal with the distribution function; a parameter search unit that compares a plurality of convolution results by the convolution processing unit with each other and searches for clutter parameters corresponding to clutter included in the received signal based on the comparison result of the plurality of convolution results; a filter calculation unit that calculates a filter for suppressing clutter contained in the received signal using the clutter parameters searched for by the parameter search unit; a clutter suppression unit that suppresses clutter included in the received signal using the filter calculated by the filter calculation unit; a threshold value determination unit that determines a threshold value to be used in CFAR (Constant False Alarm Rate) processing based on the clutter parameters searched for by the parameter search unit, The threshold value determination unit A threshold value corresponding to the clutter parameter searched for by the parameter search unit is selected from among threshold values ​​used in CFAR processing corresponding to each of a plurality of clutter parameters, the threshold values ​​being such that the false alarm probability of the CFAR processing is a designated value. A clutter suppression device characterized by:

2. The clutter parameters of the distribution function are The parameter indicates the center frequency of the clutter and the parameter indicates the frequency width of the clutter.

2. The clutter suppression device according to claim 1.

3. The convolution processing unit After repeatedly performing convolution of the received signal acquired by the received signal acquisition unit with the distribution function, the distribution function is further convolved with each of the convolution results of the received signal with the distribution function, and the convolution results of each of the convolution results with the distribution function are output.

3. The clutter suppression device according to claim 1 or 2.

4. The received signal acquisition unit acquires a received signal of a reflected wave, which is an electromagnetic wave reflected by a target; a convolution processing unit repeatedly convolves the received signal acquired by the received signal acquisition unit with the distribution function indicating a clutter distribution while updating clutter parameters of the distribution function, and outputs a plurality of convolution results of the received signal with the distribution function; a parameter search unit that compares a plurality of convolution results obtained by the convolution processing unit with each other, and searches for clutter parameters corresponding to clutter included in the received signal based on a comparison result of the plurality of convolution results; a filter calculation unit that calculates a filter for suppressing clutter contained in the received signal using the clutter parameters searched for by the parameter search unit; a clutter suppression unit that suppresses clutter contained in the received signal using the filter calculated by the filter calculation unit; a threshold value determination unit that determines a threshold value to be used in CFAR (Constant False Alarm Rate) processing based on the clutter parameters searched for by the parameter search unit; The threshold value determination unit A threshold value corresponding to the clutter parameter searched for by the parameter search unit is selected from among threshold values ​​used in CFAR processing corresponding to each of a plurality of clutter parameters, the threshold values ​​being such that the false alarm probability of the CFAR processing is a designated value. A clutter suppression method comprising:

5. an antenna that receives a reflected wave, which is an electromagnetic wave reflected by a target, and outputs a received signal of the reflected wave; a received signal acquisition unit that acquires the received signal from the antenna; a convolution processing unit that repeatedly convolves the received signal acquired by the received signal acquisition unit with the distribution function indicating a clutter distribution while updating clutter parameters of the distribution function, and outputs a plurality of convolution results of the received signal with the distribution function; a parameter search unit that compares a plurality of convolution results by the convolution processing unit with each other and searches for clutter parameters corresponding to clutter included in the received signal based on the comparison result of the plurality of convolution results; a filter calculation unit that calculates a filter for suppressing clutter contained in the received signal using the clutter parameters searched for by the parameter search unit; a clutter suppression unit that suppresses clutter included in the received signal using the filter calculated by the filter calculation unit; a threshold value determination unit that determines a threshold value to be used in CFAR (Constant False Alarm Rate) processing based on the clutter parameters searched for by the parameter search unit; a detector that detects the target by performing CFAR processing on the received signal after clutter suppression by the clutter suppression unit using the threshold determined by the threshold determination unit, The threshold value determination unit A threshold value corresponding to the clutter parameter searched for by the parameter search unit is selected from among threshold values ​​used in CFAR processing corresponding to each of a plurality of clutter parameters, the threshold values ​​being such that the false alarm probability of the CFAR processing is a designated value. A target detection device characterized by:

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