Radar signal processing device, radar device, radar signal processing method, and radar signal processing program

Abstract

To more accurately detect a target based on a beat signal.SOLUTION: A radar signal processing device includes: a filter part which generates a filter signal by filtering a processing signal based on a beat signal of a transmission signal and a reception signal using a smoothing filter in a time domain; and a detection part which detects an interference signal included in the beat signal based on the processing signal and the filter signal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a radar signal processing device, a radar device, a radar signal processing method, and a radar signal processing program. [Background technology]

[0002] Conventionally, a technique for removing an interference wave mixed in a radar reception signal is known. For example, Patent Document 1 (JP 2018-21784 A) discloses the following radar interference wave removal device. That is, the radar interference wave removal device includes: (1) a differential absolute value calculation unit that calculates a representative value or a moving average value in a predetermined time width for the absolute value of the time differential of the amplitude of the radar reception signal, real data or complex data, or (2) the absolute value of the time differential of the amplitude of the radar reception signal, and an interference wave removal unit that removes an interference wave mixed in the radar reception signal in a time region in which (1) the absolute value of the time differential of the amplitude of the radar reception signal, or (2) the representative value or the moving average value in a predetermined time width for the absolute value of the time differential of the amplitude of the radar reception signal is greater than a predetermined threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-21784 A [Patent Document 2] U.S. Patent No. 9,952,312 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for a technique that goes beyond the technique described in Patent Document 1 and is capable of detecting a target more accurately based on a beat signal.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a radar signal processing device, a radar device, a radar signal processing method, and a radar signal processing program that are capable of more accurately detecting a target based on a beat signal. [Means for solving the problem]

[0006] In order to solve the above problem, a radar signal processing device according to an aspect of the present invention includes a filter unit that generates a filter signal by filtering a processed signal, which is based on a beat signal between a transmitted signal and a received signal, with a smoothing filter in the time domain, and a detection unit that detects an interference signal included in the beat signal based on the processed signal and the filtered signal.

[0007] In this way, by using a configuration in which an interference signal is detected based on the processed signal and a filter signal generated by filtering the processed signal using a smoothing filter in the time domain, an interference signal containing interference waves of various frequencies can be detected by simple processing. In addition, since the signal level fluctuation in the azimuth direction of a beat signal is relatively large, when an interference removal process in the azimuth direction, which is generally used in conventional pulse radars, is applied to a beat signal, an interference signal may be erroneously determined. In contrast, the above configuration can suppress erroneous determination caused by the signal level fluctuation in the azimuth direction of the beat signal and detect an interference signal more accurately, so that, for example, a decrease in the signal-to-noise (SN) ratio of a power spectrum generated based on a beat signal can be suppressed. Therefore, a target can be detected more accurately based on a beat signal. Effect of the Invention

[0008] According to the present invention, a target can be detected more accurately based on a beat signal. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a diagram showing a configuration of a radar device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration of a signal processing unit in the radar device according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing a configuration of an interference removal unit in a signal processing unit according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a beat signal received by an interference removal section in a signal processing section according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing an example of a logarithmic detection value received by a filter section in an interference removal section of a signal processing section according to the embodiment of the present invention and a filter signal generated by the filter section. [Figure 6] FIG. 6 is a diagram showing an example of an interference determination flag generated by a detection unit in an interference removal unit of a signal processing unit according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of a power spectrum generated by an FFT processor in the signal processor according to the embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of logarithmic detection values ​​generated in the radar device according to the embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an example of logarithmic detection values ​​generated in the radar device according to the embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating a configuration of an interference removal unit according to a modified example of the embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram showing an example of a beat signal received by an interference removal unit in a signal processing unit according to a modified example of the embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing an example of an interference determination flag generated by a detection unit in an interference removal unit of a signal processing unit according to a modified example of the embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing an example of a window function generated by a window function generating unit in an interference removing unit of a signal processing unit according to a modified example of the embodiment of the present invention. [Figure 14] FIG. 14 is a diagram showing an example of a beat signal after FFT pre-processing by the correction unit in the interference removal unit according to the embodiment of the present invention. [Figure 15] FIG. 15 is a diagram showing an example of a beat signal after FFT pre-processing by the correction unit in the interference removal unit according to the embodiment of the present invention. [Figure 16] FIG. 16 is a diagram showing an example of a beat signal after FFT pre-processing by a correction unit in an interference removal unit according to a modification of the embodiment of the present invention. [Figure 17] FIG. 17 is a diagram showing an example of a beat signal after FFT pre-processing by a correction unit in an interference removal unit according to a modification of the embodiment of the present invention. [Figure 18] FIG. 18 is a diagram showing an example of a power spectrum generated by an FFT processor in the signal processor according to the embodiment of the present invention. [Figure 19] FIG. 19 is a flowchart defining an example of an operation procedure when the radar device according to the embodiment of the present invention performs FFT pre-processing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters and their description will not be repeated. In addition, at least some of the embodiments described below may be arbitrarily combined.

[0011] [Configuration and basic operation] <Radar device> FIG. 1 is a diagram showing a configuration of a radar device according to an embodiment of the present invention.

[0012] 1, the radar device 300 includes a radar unit 201 and a display processing unit 202. The radar unit 201 includes a signal generating unit 110, a transmitting unit 120, a transmitting antenna 130, a receiving antenna 140, a receiving unit 150, a mixer unit 160, an A / D (Analog to Digital) conversion unit 170, and a signal processing unit 100. The signal processing unit 100 is an example of a radar signal processing device. For example, the radar device 300 is an FM-CW (Frequency Modulated Continuous Wave) radar device and is mounted on a ship. The radar device 300 performs processing to display, on a display device (not shown), an echo image indicating the presence or absence of a target and the distance between the target and the target in a detection target area that is an area monitored by the ship.

[0013] The radar unit 201 outputs echo data indicating the detection result of a target in a divided target area, which is a region obtained by dividing the detection target area into a plurality of areas, to the display processing unit 202. The transmitting antenna 130 and the receiving antenna 140 rotate so that the azimuth angle of the radiation direction of radio waves from the transmitting antenna 130 changes by a predetermined angle for each predetermined sweep period T. The radar unit 201 outputs the echo data in each of the plurality of divided target areas for each sweep period T to the display processing unit 202.

[0014] The display processing unit 202 performs processing for displaying an echo image in the detection target area on a display device based on the multiple echo data received from the radar unit 201 .

[0015] <Radar section> The signal generating unit 110 repeatedly generates an analog signal of a predetermined pattern and outputs it to the transmitting unit 120. More specifically, the signal generating unit 110 outputs to the transmitting unit 120, during a sweep period T, an analog signal whose frequency increases by a predetermined amount per unit time, the analog signal having been generated using, for example, an FM-CW modulation method. Specifically, for example, the signal generating unit 110 includes a voltage generating unit and a VCO (Voltage-Controlled Oscillator). During the sweep period T, the voltage generating unit generates an FM modulated voltage whose magnitude increases at a constant rate and outputs it to the VCO. The VCO generates an analog signal having a frequency according to the magnitude of the FM modulated voltage received from the voltage generating unit and outputs it to the transmitting unit 120.

[0016] The transmitting unit 120 transmits a transmission signal. More specifically, during a sweep period T, the transmitting unit 120 generates a transmission signal in the RF (Radio Frequency) band based on an analog signal received from the signal generating unit 110, and outputs the generated transmission signal in the RF band to the division target area via the transmitting antenna 130 that rotates with the rotation of the radar unit 201. The transmitting unit 120 also outputs the generated transmission signal in the RF band to the mixer unit 160. Specifically, for example, the transmitting unit 120 includes a mixer and a power amplifier. The mixer generates a transmission signal in the RF band based on the analog signal received from the signal generating unit 110, and outputs the generated transmission signal to the power amplifier and the mixer unit 160. In the transmitting unit 120, the power amplifier amplifies the transmission signal received from the mixer, and outputs the amplified transmission signal to the division target area via the transmitting antenna 130.

[0017] The receiving unit 150 receives a reflected signal, which is a signal obtained by reflecting a transmission signal from a target object. More specifically, the receiving unit 150 receives a reflected signal in the RF band, which is a signal obtained by reflecting a transmission signal transmitted from the transmitting antenna 130 from a target object in the division target area, via the receiving antenna 140 that rotates with the rotation of the radar unit 201. The receiving unit 150 may also receive an interference wave transmitted by an interfering object via the receiving antenna 140. The interfering object may be, for example, a pulse radar device located within or outside the division target area. The receiving unit 150 outputs a signal received via the receiving antenna 140 to the mixer unit 160. Specifically, for example, the receiving unit 150 includes a low-noise amplifier. The low-noise amplifier amplifies the RF band received signal received via the receiving antenna 140, and outputs the amplified received signal to the mixer unit 160.

[0018] The mixer unit 160 generates a beat signal between the transmission signal transmitted from the radar device 300 and the reception signal received by the radar device 300. Here, the beat signal is a signal having a frequency component that is the difference between the frequency component of the transmission signal transmitted by the transmitter unit 120 and the frequency component of the reception signal received by the receiver unit 150. More specifically, the mixer unit 160 includes, for example, two mixers. A branching unit (not shown) branches the transmission signal output from the transmitter unit 120 and outputs the branched transmission signal to each mixer in the mixer unit 160 after imparting a phase difference of 90° to the branched transmission signal. In addition, a branching unit (not shown) branches the reception signal output from the receiver unit 150 and outputs the branched reception signal to each mixer in the mixer unit 160. The two mixers in the mixer unit 160 multiply the transmission signal and the reception signal, respectively, to generate an analog beat signal SA consisting of a set of an I signal Si and a Q signal Sq, and output the analog beat signal SA to the A / D conversion unit 170.

[0019] The A / D conversion unit 170 converts the analog beat signal SA received from the mixer unit 160 into a beat signal SD, which is a digital signal consisting of a set of I signals Si and Q signals Sq. More specifically, the A / D conversion unit 170 generates N beat signals SD consisting of a set of N I signals Si and N Q signals Sq by performing sampling at a predetermined sampling frequency for each sweep period T, and outputs the N beat signals SD to the signal processing unit 100. N is an integer equal to or greater than 2, for example, 1024.

[0020] The signal processing unit 100 processes the N beat signals SD received from the A / D conversion unit 170 in each sweep period T to generate echo data indicating the detection result of the target in the divided target area for each sweep period T. The signal processing unit 100 outputs the generated echo data to the display processing unit 202. Hereinafter, the beat signal SD with sample number n received by the signal processing unit 100 from the A / D conversion unit 170 in the sweep period T is also referred to as beat signal SD(n). n is an integer greater than or equal to 1 and less than or equal to N, and corresponds to the elapsed time from the start of the sweep period T. The beat signal SD(n) is a signal consisting of a set of an I signal Si(n) with sample number n and a Q signal Sq(n) with sample number n.

[0021] The radar device 300 may be configured to include one antenna that functions as the transmitting antenna 130 and the receiving antenna 140, instead of the transmitting antenna 130 and the receiving antenna 140. In this case, for example, the transmitting unit 120 transmits a transmission signal to the transmitting antenna 130 via a circulator. Also, for example, the receiving unit 150 receives a reception signal from the receiving antenna 140 via a circulator.

[0022] <Display processing section> The display processing unit 202 generates integrated data, which is the echo data in the detection target area, based on the echo data for each divided target area received from the signal processing unit 100, and performs processing to display an echo image in the detection target area on a display device (not shown) based on the generated integrated data.

[0023] <Signal processing section> 2 is a diagram showing a configuration of a signal processing unit in a radar device according to an embodiment of the present invention. Referring to Fig. 2, a signal processing unit 100 includes an interference removal unit 20, a window function processing unit 30, an FFT processing unit 40, and an absolute value / logarithm conversion unit 50.

[0024] The interference removal unit 20 receives N beat signals SD from the A / D conversion unit 170 for each sweep period T, and performs FFT pre-processing to remove interference components, which are components based on interference waves, from the components of the received beat signals SD. The interference removal unit 20 outputs the beat signals SD from which the interference components have been removed by the FFT pre-processing to the window function processing unit 30. Details of the FFT pre-processing by the interference removal unit 20 will be described later.

[0025] The window function processing unit 30 performs window function processing to multiply the N beat signals SD after the FFT processing received from the interference removal unit 20 by a predetermined window function for each sweep period T. The window function processing unit 30 outputs the beat signals SD after the window function processing to the FFT processing unit 40.

[0026] The FFT processing unit 40 generates a power spectrum P by performing FFT processing on the N beat signals SD received from the window function processing unit 30 for each sweep period T, and outputs the generated power spectrum P to the absolute value / logarithm conversion unit 50. For example, the frequency in the power spectrum P generated by the FFT processing unit 40 corresponds to the distance between the radar device 300 and a target.

[0027] The absolute value / logarithm converter 50 generates echo data by logarithmically converting the power spectrum PA indicating the absolute value of the power spectrum P received from the FFT processor 40 , and outputs the generated echo data to the display processor 202 .

[0028] <Interference removal section> Fig. 3 is a diagram showing a configuration of an interference removal unit in a signal processing unit according to an embodiment of the present invention. With reference to Fig. 3, the interference removal unit 20 includes an absolute value calculation unit 21, a logarithmic detection unit 22, an initial value calculation unit 23, a filter unit 24, a detection unit 25, and a correction unit 26. As described above, the interference removal unit 20 performs FFT pre-processing to remove interference components from the components of the beat signal SD received from the A / D conversion unit 170. The absolute value calculation unit 21 and the correction unit 26 receive the beat signal SD(n) consisting of a set of an I signal Si(n) and a Q signal Sq(n) from the A / D conversion unit 170.

[0029] The absolute value calculation unit 21 receives the beat signal SD from the A / D conversion unit 170 and calculates the absolute value a of the received beat signal SD. More specifically, the absolute value calculation unit 21 calculates the sum of the square of the value of the I signal Si(n) and the square of the value of the Q signal Sq(n) as the absolute value a(n).

[0030] The logarithmic detection unit 22 calculates a logarithmic detection value B by performing logarithmic detection of the absolute value a received from the absolute value calculation unit 21. More specifically, the logarithmic detection unit 22 receives the absolute value a(n) from the absolute value calculation unit 21, calculates 10×log{a(n)} as the logarithmic detection value B(n), and outputs the calculated logarithmic detection value B(n) to the initial value calculation unit 23, the filter unit 24, and the detection unit 25. Here, Log{A} represents the common logarithm of A.

[0031] The initial value calculation unit 23 calculates an average value AvB of the logarithmic detection values ​​B corresponding to an initial predetermined time in each sweep period T. More specifically, the initial value calculation unit 23 calculates the average value AvB from the first logarithmic detection value B(1) to the kth logarithmic detection value B(k) in the sweep period T. Here, k is an integer equal to or greater than 2 and less than N, for example, 8. The initial value calculation unit 23 outputs the calculated average value AvB to the filter unit 24.

[0032] The filter unit 24 generates an nth filtered signal A(n) by filtering the nth logarithmic detection value B(n), which is a signal based on the nth beat signal SD(n), using a smoothing filter in the time domain. The filter unit 24 outputs the generated filtered signal A(n) to the detection unit 25. The logarithmic detection value B(n) is an example of a processed signal. For example, the smoothing filter is an IIR (Infinite Impulse Response) filter, which is a type of digital filter.

[0033] For example, the filter unit 24 changes the setting of the smoothing filter based on the result of comparing the filter signal A(n-1) with the logarithmic detection value B(n) input to the smoothing filter. Specifically, the filter unit 24 changes the filtering equation as the setting of the smoothing filter.

[0034] More specifically, when the filter signal A(n-1) and the logarithmic detection value B(n) satisfy the following formula (1), the filter unit 24 generates the filter signal A(n) according to the following formula (3). On the other hand, when the filter signal A(n-1) and the logarithmic detection value B(n) satisfy the following formula (2), the filter unit 24 generates the filter signal A(n) according to the following formula (4). The predetermined threshold value ThA in formulas (1) and (2) is a value that is set in advance so that the filter signal A(n) generated by the filter unit 24 does not follow an increase in the logarithmic detection value B(n) due to an interference wave received by the receiver 150. Also, C in formula (3) is a predetermined coefficient that takes a value greater than or equal to zero and less than or equal to one. B(n)-A(n-1)≦ThA (1) B(n)-A(n-1)>ThA (2) A(n)=B(n)×C+A(n-1)×(1-C) (3) A(n)=A(n-1) (4)

[0035] Here, for example, filter unit 24 determines average value AvB of multiple logarithmic detection values ​​B(n) as the initial value of filter signal A(n). More specifically, filter unit 24 outputs average value AvB received from initial value calculation unit 23 to detection unit 25 as the initial value of filter signal A(n) during each sweep period T, regardless of equations (1) to (4).

[0036] For example, when a change in the logarithmic detection value B(n) input to the smoothing filter satisfies a predetermined condition, the filter unit 24 changes the smoothing filter to a setting that suppresses the time change of the filter signal A(n). More specifically, when the change in the logarithmic detection value B(n) input to the smoothing filter is large and therefore satisfies equation (2), the filter unit 24 suppresses the time change of the filter signal A(n) by making the nth filter signal A(n) the same value as the (n-1)th filter signal A(n-1).

[0037] Fig. 4 is a diagram showing an example of a beat signal received by an interference removal section in a signal processing section according to an embodiment of the present invention. In Fig. 4, the horizontal axis represents the value of sample number n of beat signal SD(n), and the vertical axis represents amplitude. The solid line in Fig. 4 indicates the I signal Si(n) in beat signal SD(n). The dashed line in Fig. 4 indicates the Q signal Sq(n) in beat signal SD(n).

[0038] Fig. 5 is a diagram showing an example of a logarithmic detection value received by a filter section in an interference removal section of a signal processing section according to an embodiment of the present invention and a filter signal generated by the filter section. In Fig. 5, the horizontal axis represents the value of sample number n of beat signal SD(n), and the vertical axis represents amplitude [dB]. The solid line in Fig. 5 indicates the filter signal A(n) generated by filter section 24. The dashed line in Fig. 5 indicates the logarithmic detection value B(n) received by filter section 24.

[0039] 4 and 5, due to the influence of an interference wave, the amplitudes of I signal Si(n) and Q signal Sq(n) increase suddenly when sample number n is approximately 500, causing the level of approximately the 500th logarithmic detection value B(n) to suddenly become a large value. While the filter signal A(n) generated by filter unit 24 follows the gradual change in the level of the logarithmic detection value B(n), it does not follow the sudden change in the level of the logarithmic detection value B(n).

[0040] The detector 25 detects the interference signal contained in the beat signal SD(n) based on the logarithmic detection value B(n) and the filtered signal A(n).

[0041] For example, the detector 25 detects an interference signal based on a comparison result between the logarithmic detection value B(n) and the filtered signal A(n). More specifically, the detector 25 detects an interference signal based on a difference or ratio with respect to the filtered signal A(n).

[0042] Specifically, the detection unit 25 determines that an interference signal is included in the beat signal SD(n) when the logarithmic detection value B(n) received from the logarithmic detection unit 22 and the filter signal A(n) received from the filter unit 24 satisfy the following formula (5), where ThB is a predetermined threshold value. B(n)-A(n)≧ThB (5)

[0043] 6 is a diagram showing an example of an interference determination flag generated by a detection unit in an interference removal unit of a signal processing unit according to an embodiment of the present invention, in which the horizontal axis indicates the value of sample number n of the beat signal SD, and the vertical axis indicates the flag value.

[0044] 6, the detection unit 25 generates an interference determination flag in which the flag value corresponding to the sample number n of the beat signal SD(n) determined to include an interference signal is 1, and the flag value corresponding to the sample number n of the beat signal SD(n) not determined to include an interference signal is 0. Specifically, the detection unit 25 generates an interference determination flag in which the flag value is 1 when the sample number n is approximately 500. The detection unit 25 outputs the generated interference determination flag to the correction unit 26.

[0045] The correction unit 26 performs signal processing, i.e., FFT pre-processing, to attenuate the amplitude of the interference signal. More specifically, the correction unit 26 receives the beat signal SD(n) from the A / D conversion unit 170, and performs FFT pre-processing to attenuate the amplitude of the beat signal SD(n) of sample number n when the flag value of the interference determination flag received from the detection unit 25 is 1, out of the received beat signal SD(n). Hereinafter, the sample number n when the flag value of the interference determination flag is 1 is defined as nx.

[0046] For example, as FFT pre-processing, the correction unit 26 replaces the amplitudes of the I signal Si(n) and the Q signal Sq(n) of sample number nx, among the I signal Si(n) and the Q signal Sq(n) in the received beat signal SD(n), with zero. The correction unit 26 outputs the beat signal SD(n) after the FFT pre-processing to the window function processing unit 30.

[0047] 2 again, as described above, the window function processing unit 30 performs window function processing on the beat signal SD(n) after the FFT processing received from the interference removal unit 20, and outputs the beat signal SD(n) after the window function processing to the FFT processing unit 40. Then, the FFT processing unit 40 performs FFT processing on the beat signal SD received from the window function processing unit 30 to generate a power spectrum.

[0048] Fig. 7 is a diagram showing an example of a power spectrum generated by an FFT processing unit in a signal processing unit according to an embodiment of the present invention. In Fig. 7, the horizontal axis is frequency, and the vertical axis is amplitude [dB]. The solid line in Fig. 7 shows an example of a power spectrum P1 generated by the FFT processing unit 40 when FFT pre-processing is performed by the interference removal unit 20. The dashed line in Fig. 7 shows an example of a power spectrum P2 generated by the FFT processing unit 40 when FFT pre-processing is not performed.

[0049] 7, the power spectrum P2 generated by the FFT processor 40 when FFT pre-processing is not performed has a low S / N ratio due to the influence of interference waves. In contrast, the power spectrum P1 generated by the FFT processor 40 when FFT pre-processing is performed by the interference remover 20 has a higher S / N ratio than the power spectrum P2, and peaks can be detected more accurately. This allows targets in the detection area to be detected correctly.

[0050] Incidentally, for example, in conventional pulse radars, a detection method is generally used in which interference signals are detected based on the results of comparing the signal levels of received signals in the azimuth direction. Specifically, in conventional pulse radars, for example, the signal levels of received signals in adjacent divided target areas are compared, and a received signal having a prominent amplitude compared to the received signal in the adjacent divided target area is determined to contain an interference signal.

[0051] However, when the above detection method used in pulse radar is applied to, for example, an FM-CW radar device, the S / N ratio of the power spectrum may decrease.

[0052] 8 and 9 are diagrams showing an example of a logarithmic detection value generated in a radar device according to an embodiment of the present invention. FIG. 9 is an enlarged view of an area R1 in FIG. 8. In FIG. 8 and FIG. 9, the horizontal axis indicates the value of sample number n of the beat signal SD(n), and the vertical axis indicates the amplitude [dB]. The solid line in FIG. 8 and FIG. 9 indicates a logarithmic detection value B1(n) based on the beat signal SD1(n) corresponding to the division target area Ar1. The dashed line in FIG. 8 and FIG. 9 indicates a logarithmic detection value B2(n) based on the beat signal SD2(n) corresponding to the division target area Ar2 adjacent to the division target area Ar1. The dashed line in FIG. 8 and FIG. 9 indicates a logarithmic detection value B3(n) based on the beat signal SD3(n) corresponding to the division target area Ar3 adjacent to the division target area Ar2.

[0053] In FIG. 8, the amplitude spikes exceeding, for example, 50 dB in the logarithmic detection values ​​B1(n), B2(n), and B3(n) are due to the influence of interference waves.

[0054] 9, the logarithmic detection values ​​B1(n), B2(n), and B3(n) may have different amplitudes even when the amplitude is 50 dB or less and there is no influence of interference waves. Therefore, in an FM-CW radar device, when an attempt is made to detect an interference signal based on a comparison result of the signal level in the azimuth direction of the logarithmic detection value B as in the above detection method in a pulse radar, it is erroneously determined that the logarithmic detection value B in a state where there is no influence of interference waves contains an interference signal. Then, when the erroneously determined interference signal is removed, the signal-to-noise ratio of the generated power spectrum may decrease.

[0055] In contrast, in the signal processing unit 100 according to the embodiment of the present invention, an interference signal is detected based on the logarithmic detection value B and a filtered signal generated by filtering the logarithmic detection value B in the time domain using a smoothing filter. This configuration makes it possible to suppress erroneous determination of the interference signal and detect the interference signal more accurately than a configuration in which an interference signal is detected based on a comparison result of the signal level in the azimuth direction of the logarithmic detection value B. Therefore, it is possible to suppress a decrease in the S / N ratio of the power spectrum P generated based on the beat signal SD.

[0056] [Variations] Fig. 10 is a diagram showing a configuration of an interference removal unit according to a modified example of the embodiment of the present disclosure. With reference to Fig. 10, compared to the interference removal unit 20, the interference removal unit 20A includes a correction unit 26A instead of the correction unit 26, and further includes a window function generation unit 27. The signal processing unit 100 may be configured to include the interference removal unit 20A instead of the interference removal unit 20.

[0057] Fig. 11 is a diagram showing an example of a beat signal received by an interference removal section in a signal processing section according to a modified example of an embodiment of the present invention. In Fig. 11, the horizontal axis represents the value of sample number n of beat signal SD(n), and the vertical axis represents amplitude. The solid line in Fig. 11 indicates the I signal Si(n) in beat signal SD(n). The dashed line in Fig. 11 indicates the Q signal Sq(n) in beat signal SD(n).

[0058] Referring to FIG. 11, due to the influence of the interference wave, the amplitudes of the I signal Si(n) and the Q signal Sq(n) when sample number n is approximately 100, and the I signal Si(n) and the Q signal Sq(n) when sample number n is approximately 480, increase rapidly.

[0059] 12 is a diagram showing an example of an interference determination flag generated by a detection unit in an interference removal unit of a signal processing unit according to a modified example of the embodiment of the present invention, in which the horizontal axis indicates the value of sample number n of the beat signal SD, and the vertical axis indicates the flag value.

[0060] 12, the detection unit 25 generates an interference determination flag whose flag value is 1 when the sample number n is about 100 and whose flag value is 1 when the sample number n is about 480. The detection unit 25 outputs the generated interference determination flag to the window function generation unit 27.

[0061] The window function generating unit 27 receives the interference determination flag from the detecting unit 25 and generates a window function Wf based on the received interference determination flag.

[0062] 13 is a diagram showing an example of a window function generated by a window function generating unit in an interference canceller of a signal processing unit according to a modified example of the embodiment of the present invention, in which the horizontal axis indicates the value of sample number n of the beat signal SD, and the vertical axis indicates a coefficient Wc of the window function.

[0063] 13, the window function generating unit 27 generates a window function Wf in which the coefficient Wc of sample number nx is zero when the flag value of the interference determination flag is 1, and the coefficient Wc increases linearly and approaches 1 as the sample number n increases or decreases from nx. The window function generating unit 27 outputs the generated window function Wf to the correction unit 26A. Note that the window function generating unit 27 may be configured to generate a window function Wf in which the coefficient Wc increases curvilinearly, such as a sine curve, as the sample number n increases or decreases from nx.

[0064] The correction unit 26A performs signal processing, i.e., FFT pre-processing, to attenuate the amplitude of the beat signal SD(n) in a region including an interference signal by multiplying the beat signal SD(n) by a window function Wf. More specifically, the correction unit 26A receives the beat signal SD(n) from the A / D conversion unit 170, and performs window function processing to multiply the received beat signal SD(n) by the window function Wf received from the window function generation unit 27. The correction unit 26A outputs the beat signal SD(n) after the window function processing to the window function processing unit 30.

[0065] Fig. 14 and Fig. 15 are diagrams showing an example of a beat signal after FFT pre-processing by the correction unit in the interference removal unit according to the embodiment of the present invention. Fig. 15 is an enlarged view of region R2 in Fig. 14. In Fig. 14 and Fig. 15, the horizontal axis indicates the value of sample number n of the beat signal SD(n), and the vertical axis indicates the amplitude. The solid lines in Fig. 14 and Fig. 15 indicate the I signal Si(n) in the beat signal SD(n) after FFT pre-processing by the correction unit 26. The dashed lines in Fig. 14 and Fig. 15 indicate the Q signal Sq(n) in the beat signal SD(n) after FFT pre-processing by the correction unit 26.

[0066] Fig. 16 and Fig. 17 are diagrams showing an example of a beat signal after FFT pre-processing by the correction unit in the interference removal unit according to the modified embodiment of the present invention. Fig. 17 is an enlarged view of region R3 in Fig. 15. In Fig. 16 and Fig. 17, the horizontal axis indicates the value of sample number n of the beat signal SD(n), and the vertical axis indicates the amplitude. The solid lines in Fig. 16 and Fig. 17 indicate the I signal Si(n) in the beat signal SD(n) after FFT pre-processing by the correction unit 26A. The dashed lines in Fig. 16 and Fig. 17 indicate the Q signal Sq(n) in the beat signal SD(n) after FFT pre-processing by the correction unit 26A.

[0067] 15 and 17, in the beat signal SD(n) after FFT pre-processing by correction unit 26, the amplitudes of the I signal Si(nx) and Q signal Sq(nx) of sample number nx when the flag value of the interference determination flag is 1 are replaced with zero, so that the I signal Si(n) and Q signal Sq(n) of sample number n before and after nx change suddenly, that is, a discontinuous point occurs. In contrast, in the beat signal SD(n) after FFT pre-processing by correction unit 26A, the beat signal SD(n) is multiplied by the window function Wf, so that the amplitudes of the I signal Si(n) and Q signal Sq(n) of sample number n before and after nx change gradually without increasing or decreasing suddenly, and no discontinuous point occurs.

[0068] Fig. 18 is a diagram showing an example of a power spectrum generated by an FFT processing unit in a signal processing unit according to an embodiment of the present invention. In Fig. 18, the horizontal axis is frequency, and the vertical axis is amplitude [dB]. The solid line in Fig. 18 indicates a power spectrum P3 generated by the FFT processing unit 40 when FFT pre-processing is performed by the interference removal unit 20. The dashed line in Fig. 18 indicates a power spectrum P4 generated by the FFT processing unit 40 when FFT pre-processing is performed by the interference removal unit 20A according to a modified example.

[0069] Referring to FIG. 18, power spectrum P4 is a power spectrum generated based on beat signal SD(n) that does not have a discontinuous point, and therefore has smaller range side lobes than power spectrum P3.

[0070] [Operation flow] The radar device according to the embodiment of the present invention includes a computer including a memory, and a processor such as a CPU in the computer reads out from the memory and executes a program including some or all of the steps of the following flowcharts and sequences. This program can be installed from an external source. This program is distributed in a state stored on a recording medium.

[0071] FIG. 19 is a flowchart defining an example of an operation procedure when the radar device according to the embodiment of the present invention performs FFT pre-processing.

[0072] 19, first, the radar device 300 calculates the absolute value a(n) of the beat signal SD(n) (step S102).

[0073] Next, the radar device 300 calculates a logarithmic detection value B(n) by performing logarithmic detection of the absolute value a(n) (step S104).

[0074] Next, the radar device 300 generates a filtered signal A(n) by filtering the logarithmic detection value B(n) in the time domain using a smoothing filter (step S106).

[0075] Next, the radar device 300 detects an interference signal included in the beat signal SD(n) based on the logarithmic detection value B(n) and the filtered signal A(n) (step S108).

[0076] Next, the radar device 300 performs FFT pre-processing to attenuate the amplitude of the interference signal (step S110).

[0077] Although the signal processing unit 100 according to the embodiment of the present invention has been described as including the correction unit 26, the present invention is not limited to this. The signal processing unit 100 may be configured not to include the correction unit 26. In this case, for example, the signal processing unit 100 includes a notification unit that notifies the outside of the signal processing unit 100 of the detection result of the interference signal by the detection unit 25.

[0078] In the signal processing unit 100 according to the embodiment of the present invention, the filter unit 24 is configured to determine the average value AvB of the multiple logarithmic detection values ​​B(n) as the initial value of the filter signal A(n), but this is not limited to this. The filter unit 24 may be configured to determine a preset value as the initial value of the filter signal A(n).

[0079] Meanwhile, a technique capable of more accurately detecting a target based on a beat signal is desired.

[0080] For example, the technology described in Patent Document 1 determines whether or not an interference wave is mixed into a radar reception signal based on the absolute value of the time derivative of the amplitude of the radar reception signal. With the technology described in Patent Document 1, it is difficult to detect, for example, low-frequency interference waves and interference waves having a constant frequency. Furthermore, with the technology described in Patent Document 2, it is necessary to perform processing such as Fourier transform to detect interference waves, which results in a large circuit scale.

[0081] In contrast, in the signal processing unit 100 according to the embodiment of the present invention, the filter unit 24 generates a filter signal A(n) by filtering, in the time domain, a logarithmic detection value B(n) based on a beat signal SD(n) between a transmission signal and a reception signal, using a smoothing filter. The detector 25 detects an interference signal included in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n).

[0082] In this way, by using a configuration in which an interference signal is detected based on the logarithmic detection value B(n) and the filtered signal A(n) generated by filtering the logarithmic detection value B(n) in the time domain using a smoothing filter, an interference signal containing interference waves of various frequencies can be detected by simple processing. In addition, since the beat signal SD(n) has a relatively large signal level fluctuation in the azimuth direction, when an interference removal process in the azimuth direction, which is generally used in conventional pulse radars, is applied to the beat signal SD(n), an interference signal may be erroneously determined. In contrast, the above configuration can suppress erroneous determination caused by the signal level fluctuation in the azimuth direction of the beat signal and detect the interference signal more accurately, thereby suppressing a decrease in the S / N ratio of the power spectrum P generated based on the beat signal SD(n). Therefore, a target can be detected more accurately based on the beat signal SD(n).

[0083] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, the filter unit 24 changes the settings of the smoothing filter based on the result of the comparison between the filtered signal A(n-1) and the logarithmic detection value B(n).

[0084] With this configuration, it is possible to generate a filtered signal A(n) that can more reliably detect an interference signal, according to the comparison result between the filtered signal A(n-1) and the logarithmic detection value B(n).

[0085] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, when a change in the logarithmic detection value B(n) input to the smoothing filter satisfies a predetermined condition, the filter unit 24 changes the setting of the smoothing filter to one that further suppresses the time change of the filtered signal A(n).

[0086] With this configuration, it is possible to suppress missed detection of interference signals due to the filter signal A(n) following changes in the logarithmic detection value B(n), and generate a filter signal A(n) that can more reliably detect interference signals.

[0087] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, the detection unit 25 detects an interference signal based on the result of comparison between the logarithmic detection value B(n) and the filtered signal A(n).

[0088] With this configuration, it is possible to detect an interference signal through simple processing using the generated filtered signal A(n) and the logarithmic detection value B(n).

[0089] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, the detection unit 25 detects an interference signal based on the difference or ratio between the logarithmic detection value B(n) and the filtered signal A(n).

[0090] With this configuration, it is possible to more accurately detect an interference signal with simple processing by using a preset threshold value related to the difference or ratio between the filtered signal A(n) and the logarithmic detection value B(n).

[0091] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, the correction unit 26 performs signal processing to attenuate the amplitude of the interference signal.

[0092] With this configuration, the interference wave components contained in the beat signal SD(n) can be attenuated, so that the corrected beat signal SD(n) can be used to more accurately detect a target.

[0093] Moreover, in the signal processing unit 100 according to the embodiment of the present invention, the correction unit 26A performs signal processing to attenuate the amplitude of the beat signal SD(n) in a region including an interference signal by multiplying the beat signal SD(n) by a window function Wf.

[0094] With this configuration, it is possible to suppress a sudden increase or decrease in the amplitude of the beat signal SD(n) after the correction processing, and therefore it is possible to suppress an increase in the range side lobe in the power spectrum P generated by performing FFT processing on the beat signal SD(n).

[0095] Furthermore, in the signal processing unit 100 according to the embodiment of the present invention, the filter unit 24 determines the average value AvB of the logarithmic detection value B(n) at a predetermined time as the initial value of the filter signal A(n).

[0096] With this configuration, the filter signal A(n) can be generated using the determined initial value and recursive function.

[0097] Moreover, in the signal processing unit 100 according to the embodiment of the present invention, the smoothing filter used in the filter unit 24 is an IIR filter.

[0098] With this configuration, compared to a configuration in which a filter signal A(n) is generated using an FIR filter, it is possible to generate a filter signal A(n) that does not follow a steep increase or decrease in the logarithmic detection value B(n), thereby suppressing erroneous detection of an interference signal.

[0099] Moreover, the radar device 300 according to the embodiment of the present invention includes a signal processing unit 100, a transmitting unit 120, and a receiving unit 150. The transmitting unit 120 transmits a transmission signal. The receiving unit 150 receives a reflected signal, which is a signal that is the transmitted transmission signal reflected by a target.

[0100] With this configuration, it is possible to realize a radar device 300 that detects a target more accurately based on the beat signal SD(n) and the logarithmic detection value B(n).

[0101] In the radar device 300 according to the embodiment of the present invention, the transmitter 120 transmits a transmission signal via the rotating transmission antenna 130. The receiver 150 receives a reflected signal via the rotating reception antenna 140.

[0102] With this configuration, it is possible to transmit signals in various directions and receive reflected signals, making it possible to detect targets over a wider range.

[0103] Moreover, the radar signal processing method according to the embodiment of the present invention is a radar signal processing method in the signal processing unit 100 used in the radar device 300. In this radar signal processing method, first, a logarithmic detection value B(n) based on a beat signal SD(n) between a transmission signal and a reception signal is filtered in the time domain using a smoothing filter to generate a filter signal A(n). Next, the signal processing unit 100 detects an interference signal included in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n).

[0104] In this way, by using a method for detecting an interference signal based on the logarithmic detection value B(n) and the filtered signal A(n) generated by filtering the logarithmic detection value B(n) in the time domain using a smoothing filter, an interference signal containing interference waves of various frequencies can be detected by simple processing. In addition, since the signal level fluctuation in the azimuth direction of the beat signal SD(n) is relatively large, when the interference removal processing in the azimuth direction generally used in conventional pulse radars is applied to the beat signal, the interference signal may be erroneously determined. In contrast, the above method can suppress erroneous determination caused by the signal level fluctuation in the azimuth direction of the beat signal SD(n) and detect the interference signal more accurately, thereby suppressing a decrease in the S / N ratio of the power spectrum P generated based on the beat signal SD(n). Therefore, a target can be detected more accurately based on the beat signal SD(n).

[0105] The above-described embodiments should be considered as illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0106] 20,20A Interference removal section 21 Absolute value calculation section 22 Logarithmic detection section 23 Initial value calculation section 24 Filter section 25 Detection unit 26,26A correction section 27 Window function generator 30 Window function processing section 40 FFT processing section 50 Absolute value / logarithm conversion section 100 Signal processing section 110 Signal Generator 120 Transmitter 130 Transmitting Antenna 140 Receiving Antenna 150 Receiver 160 Mixer section 170 A / D conversion section 201 Radar Section 202 Display processing unit 300 Radar Equipment

Claims

1. a filter unit that generates a filtered signal by filtering a processed signal based on a beat signal between a transmission signal and a reception signal using a smoothing filter in a time domain; a detection unit that detects an interference signal included in the beat signal based on the processed signal and the filtered signal, The filter unit changes a setting of the smoothing filter based on a comparison result between the filtered signal and the processed signal.

2. The radar signal processing device according to claim 1 , wherein the filter unit changes the setting of the smoothing filter to a setting that further suppresses the time change of the filter signal when a change in the processed signal input to the smoothing filter satisfies a predetermined condition.

3. 3. The radar signal processing device according to claim 1, wherein the detection unit detects the interference signal based on a result of comparison between the processed signal and the filtered signal.

4. The radar signal processing device according to claim 3 , wherein the detection unit detects the interference signal based on a difference or a ratio between the processed signal and the filtered signal.

5. The radar signal processing device further includes: The radar signal processing device according to claim 1 , further comprising a correction unit that performs signal processing to attenuate the amplitude of the interference signal.

6. The radar signal processing device according to claim 5 , wherein the correction unit performs the signal processing to attenuate an amplitude of the beat signal in a region including the interference signal by multiplying the beat signal by a window function.

7. 7. The radar signal processing device according to claim 1, wherein the filter section determines an average value of the processed signal over a predetermined time period as an initial value of the filtered signal.

8. The radar signal processing device according to claim 1 , wherein the smoothing filter is an IIR filter.

9. The smoothing filter is an IIR filter, the filter unit sets the smoothing filter to generate, when a comparison result between the filter signal and the processed signal input to the smoothing filter satisfies a predetermined first condition, the filter signal corresponding to a second time later than the first time, based on the processed signal and the filter signal corresponding to a first time; 2. The radar signal processing device according to claim 1, wherein, when a comparison result between the filter signal and the processed signal input to the smoothing filter satisfies a predetermined second condition, the filter unit sets the smoothing filter to generate the filter signal in which time change is suppressed more than the filter signal generated when the first condition is satisfied.

10. A radar signal processing device according to any one of claims 1 to 9, A transmitter for transmitting the transmission signal; a receiving unit that receives a reflected signal, which is a signal that is the transmitted signal reflected by a target.

11. The transmitter transmits the transmission signal via a rotating antenna, The radar device according to claim 10 , wherein the receiver receives the reflected signal via a rotating antenna.

12. A radar signal processing method in a radar signal processing device, comprising: generating a filtered signal by filtering a processed signal based on a beat signal between a transmission signal and a reception signal using a smoothing filter in a time domain; detecting an interference signal included in the beat signal based on the processed signal and the filtered signal; and changing settings of the smoothing filter based on a comparison result between the filtered signal and the processed signal.

13. A radar signal processing program for use in a radar signal processing device, comprising: A process of generating a filtered signal by filtering a processed signal based on a beat signal between a transmission signal and a reception signal using a smoothing filter in the time domain; and detecting an interference signal included in the beat signal based on the processed signal and the filtered signal, A radar signal processing program that changes settings of the smoothing filter based on a comparison result between the filtered signal and the processed signal.

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