Radar signal processing device, method and radar device and storage medium

Abstract

Provided are a radar signal processing device, method, and radar device that can more accurately detect a target based on a beat signal, and a storage medium. The radar signal processing device includes a filter section that generates a processing signal based on a beat signal obtained from a transmission signal and a reception signal, and filters the processing signal using a smoothing filter in a time region to generate a smoothed signal, and a detection section that detects an interference signal contained in the beat signal based on the processing signal and the smoothed signal.

Description

Technical Field

[0001] This 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] Previously, a technique for removing interference waves mixed in with radar received signals was known. For example, Patent Document 1 (Japanese Patent Application Publication No. 2018-21784) discloses a radar interference wave removal device as described below. That is, the radar interference wave removal device includes: a differential absolute value calculation unit that calculates the absolute value of the time derivative of (1) real or complex data of the amplitude of the radar received signal or (2) the representative value or moving average value of the absolute value of the time derivative of the real or complex data of the amplitude of the radar received signal within a specified time width; and an interference wave removal unit that removes interference waves mixed in with the radar received signal within a time region in which the representative value or moving average value of the absolute value of the time derivative of the amplitude of the radar received signal (1) or (2) within a specified time width is greater than a specified threshold.

[0003] [Existing Technical Documents]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-21784

[0006] [Patent Document 2] US Patent No. 9952312 Specification Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] The goal is to develop a technology that can detect targets more accurately based on beat signals, exceeding the technology described in this patent document 1.

[0009] The present invention was made to solve the aforementioned problems, and its purpose is to provide a radar signal processing device, radar device, radar signal processing method, and radar signal processing program that can more accurately detect targets based on beat signals.

[0010] [Technical means to solve the problem]

[0011] To address the aforementioned problem, a radar signal processing apparatus according to one aspect of the present invention includes: a filter unit that generates a processed signal based on a beat signal obtained from a transmitted signal and a received signal, and generates a smoothed signal by filtering the processed signal using a smoothing filter in a time region; and a detection unit that detects an interference signal contained in the beat signal based on the processed signal and the smoothed signal.

[0012] Thus, by detecting interference signals based on a smoothed signal generated by filtering the processed signal using a smoothing filter in the time region, and the processed signal, this structure allows for the detection of interference signals containing interfering waves of multiple frequencies using simple processing. Furthermore, the signal level variation in the azimuth direction of the beat signal is relatively large. Therefore, when applying the azimuth interference removal processing commonly used in conventional pulse radar to beat signals, misjudgments of the interference signal can sometimes occur. In contrast, with the aforementioned structure, misjudgments caused by the azimuth signal level variation of the beat signal can be suppressed, thereby enabling more accurate detection of the interference signal. This also suppresses, for example, the decrease in the signal-to-noise (SN) ratio of the power spectrum generated based on the beat signal. Therefore, targets can be detected more accurately based on the beat signal.

[0013] [The effects of the invention]

[0014] According to the present invention, targets can be detected more accurately based on beat signals. Attached Figure Description

[0015] Figure 1 This is a diagram showing the structure of a radar device according to an embodiment of the present invention.

[0016] Figure 2 This is a diagram showing the structure of the signal processing unit in a radar device according to an embodiment of the present invention.

[0017] Figure 3 This is a diagram showing the structure of the interference removal unit in the signal processing unit according to an embodiment of the present invention.

[0018] Figure 4 This diagram illustrates an example of a beat signal received by the interference removal unit in the signal processing unit according to an embodiment of the present invention.

[0019] Figure 5 This diagram illustrates an example of the logarithmic detection value received by the filter unit in the interference removal unit of the signal processing unit according to an embodiment of the present invention, and the filter signal generated by the filter unit.

[0020] Figure 6This diagram illustrates an example of an interference determination mark generated by the detection unit in the interference removal unit of the signal processing unit according to an embodiment of the present invention.

[0021] Figure 7 This is a diagram illustrating an example of the power spectrum generated by the Fast Fourier Transform (FFT) processing unit in the signal processing unit of an embodiment of the present invention.

[0022] Figure 8 This is a diagram showing an example of the logarithmic detection values ​​generated in the radar device according to an embodiment of the present invention.

[0023] Figure 9 This is a diagram showing an example of the logarithmic detection values ​​generated in the radar device according to an embodiment of the present invention.

[0024] Figure 10 This is a diagram showing the structure of the interference removal unit in a modified embodiment of the present disclosure.

[0025] Figure 11 This is a diagram illustrating an example of a beat signal received by the interference removal unit in the signal processing unit of a modified embodiment of the present invention.

[0026] Figure 12 This diagram illustrates an example of an interference determination mark generated by the detection unit in the interference removal unit of the signal processing unit according to a modified embodiment of the present invention.

[0027] Figure 13 This is a diagram illustrating an example of a window function generated by the window function generation unit in the interference removal unit of the signal processing unit according to a modified embodiment of the present invention.

[0028] Figure 14 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of an embodiment of the present invention.

[0029] Figure 15 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of an embodiment of the present invention.

[0030] Figure 16 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of a modified embodiment of the present invention.

[0031] Figure 17 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of a modified embodiment of the present invention.

[0032] Figure 18This is a diagram showing an example of the power spectrum generated by the FFT processing unit in the signal processing unit of an embodiment of the present invention.

[0033] Figure 19 This is a flowchart that specifies an example of the operation flow when performing FFT preprocessing on a radar device according to an embodiment of the present invention.

[0034] [Explanation of Symbols]

[0035] 20, 20A: Interference Removal Section

[0036] 21: Absolute Value Calculation Department

[0037] 22: Logarithmic Detector

[0038] 23: Initial Value Calculation Section

[0039] 24: Filter Section

[0040] 25: Testing Department

[0041] 26, 26A: Correction Section

[0042] 27: Window Function Generation Section

[0043] 30: Window Function Processing Section

[0044] 40: FFT Processing Department

[0045] 50: Absolute / Logarithmic Transformation Section

[0046] 100: Signal Processing Department

[0047] 110: Signal Generation Unit

[0048] 120: Dispatch Department

[0049] 130: Transmitting antenna

[0050] 140: Receiving antenna

[0051] 150: Receiving Department

[0052] 160: Mixer Section

[0053] 170: A / D Conversion Section

[0054] 201: Radar Department

[0055] 202: Display Processing Unit

[0056] 300: Radar device Detailed Implementation

[0057] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Furthermore, identical or equivalent parts in the drawings will be labeled with the same symbols and their descriptions will not be repeated. Moreover, at least some of the embodiments described below may be combined arbitrarily.

[0058] [Structure and basic movements]

[0059] Radar Device

[0060] Figure 1 This is a diagram showing the structure of a radar device according to an embodiment of the present invention.

[0061] Reference Figure 1 The radar device 300 includes a radar unit 201 and a display processing unit 202. The radar unit 201 includes a signal generation unit 110, a transmission unit 120, a transmission antenna 130, a receiving antenna 140, a receiving unit 150, a mixer unit 160, an analog-to-digital (A / D) converter 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 a frequency-modulated continuous wave (FM-CW) radar device mounted on a ship. The radar device 300 performs the following processing: displays the echo image (not shown) of the presence or absence of targets and the distance to targets in the area monitored by the ship (i.e., the target area) on the display device.

[0062] The radar unit 201 outputs echo data to the display processing unit 202. This echo data represents the detection results of targets within the segmented target areas, which are divided into multiple regions. The transmitting antenna 130 and the receiving antenna 140 are rotated such that the azimuth angle of the transmitting antenna 130 relative to the radiation direction of the radio waves changes by a predetermined angle every predetermined sweep period T. The radar unit 201 outputs echo data from the multiple segmented target areas for each sweep period T to the display processing unit 202.

[0063] The display processing unit 202 performs the following processing: based on multiple echo data received from the radar unit 201, it displays an echo image of the detection target area on a display device.

[0064] Radar Department

[0065] The signal generation unit 110 repeatedly generates analog signals of a predetermined pattern and outputs them to the transmission unit 120. More specifically, during the sweep period T, the signal generation unit 110 outputs an analog signal generated by a modulation method such as FM-CW, whose frequency increases by a predetermined amount per unit time, to the transmission unit 120. Specifically, for example, the signal generation unit 110 includes a voltage generation unit and a voltage-controlled oscillator (VCO). During the sweep period T, the voltage generation unit generates an FM modulation voltage whose magnitude increases at a fixed ratio and outputs it to the VCO. The VCO generates an analog signal with a frequency corresponding to the magnitude of the FM modulation voltage received from the voltage generation unit and outputs it to the transmission unit 120.

[0066] The transmitting unit 120 transmits a transmission signal. More specifically, during the sweep period T, the transmitting unit 120 generates a radio frequency (RF) band transmission signal based on the analog signal received from the signal generation unit 110, and outputs the generated RF band transmission signal to the segmented target area via the transmitting antenna 130, which rotates along with the rotation of the radar unit 201. Furthermore, the transmitting unit 120 outputs the generated RF band transmission signal to the mixer unit 160. Specifically, for example, the transmitting unit 120 includes a mixer and a power amplifier. The mixer generates an RF band transmission signal based on the analog signal received from the signal generation 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 segmented target area via the transmitting antenna 130.

[0067] The receiving unit 150 receives the reflected signal, i.e., the signal reflected from the target, which is the transmitted signal. More specifically, the receiving unit 150 receives the reflected signal, i.e., the RF band signal, which is the signal reflected from the target area by the transmitted signal transmitted from the transmitting antenna 130, via the receiving antenna 140, which rotates along with the radar unit 201. Furthermore, the receiving unit 150 may also receive interference waves emitted by interfering objects via the receiving antenna 140. Interfering objects may be, for example, pulse radar devices located within or outside the target area. The receiving unit 150 outputs the 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.

[0068] The mixer unit 160 generates a beat signal between the transmitted signal sent from the radar device 300 and the received signal received by the radar device 300. Here, the beat signal is a signal having a frequency component that differs between the frequency components of the transmitted signal sent from the transmitting unit 120 and the frequency components of the received signal received by the receiving unit 150. More specifically, the mixer unit 160 includes, for example, two mixers. A branch (not shown) branches the transmitted signal output from the transmitting unit 120 and assigns a 90° phase difference to the branched transmitted signal before outputting it to each mixer in the mixer unit 160. Similarly, a branch (not shown) branches the received signal output from the receiving unit 150 and outputs it to each mixer in the mixer unit 160. The two mixers in the mixer unit 160 perform multiplication operations on the transmitted and received signals respectively, thereby generating an analog beat signal SA comprising a group of I signals Si and Q signals Sq, which is then output to the A / D converter 170.

[0069] The A / D converter 170 converts the analog beat signal SA received from the mixer 160 into a digital signal SD, which consists of groups of I signals Si and Q signals Sq. More specifically, the A / D converter 170 samples at a predetermined sampling frequency during each sweep period T, thereby generating N beat signals SD, which consist of groups of N I signals Si and N Q signals Sq, and outputs them to the signal processing unit 100. N is an integer greater than or equal to 2, for example, 1024.

[0070] During each sweep period T, the signal processing unit 100 processes the N beat signals SD received from the A / D conversion unit 170 to generate echo data representing the detection results of the target in the segmented target area during 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 the sampling number n received by the signal processing unit 100 from the A / D conversion unit 170 during the sweep period T will also be referred to as the beat signal SD(n). n is an integer of 1 or more and N less, corresponding to the elapsed time counted from the start of the sweep period T. The beat signal SD(n) is a group of signals including the I signal Si(n) with the sampling number n and the Q signal Sq(n) with the sampling number n.

[0071] Alternatively, the radar device 300 may be structured to include a single antenna that functions as both the transmitting antenna 130 and the receiving antenna 140, replacing the transmitting antenna 130 and the receiving antenna 140. In this case, for example, the transmitting unit 120 transmits the transmitting signal to the transmitting antenna 130 via a circulator. Furthermore, for example, the receiving unit 150 receives the receiving signal from the receiving antenna 140 via a circulator.

[0072] Display Processing Department

[0073] The display processing unit 202 performs the following processing: based on the echo data of each segmented target region received from the signal processing unit 100, it generates echo data, i.e., composite data, in the target region, and displays the echo image in the target region on a display device (not shown) based on the generated composite data.

[0074] <Signal Processing Department>

[0075] Figure 2 This is a diagram showing the structure of the signal processing unit in a radar device according to an embodiment of the present invention. (Refer to...) Figure 2 The signal processing unit 100 includes an interference removal unit 20, a window function processing unit 30, an FFT processing unit 40, and an absolute / logarithmic conversion unit 50.

[0076] The interference removal unit 20 performs FFT preprocessing as described below: during each sweep period T, it receives N beat signals SD from the A / D conversion unit 170 and removes the interference components (based on the interference wave) from the components of the received beat signals SD. The interference removal unit 20 then outputs the beat signals SD, after the interference components have been removed through the FFT preprocessing, to the window function processing unit 30. Details of the FFT preprocessing performed by the interference removal unit 20 will be described later.

[0077] During each sweep period T, the window function processing unit 30 performs window function processing, multiplying the N beat signals SD received from the interference removal unit 20 after FFT processing by a predetermined window function. The window function processing unit 30 then outputs the window function-processed beat signals SD to the FFT processing unit 40.

[0078] During each sweep period T, the FFT processing unit 40 performs FFT processing on the N beat signals SD received from the window function processing unit 30 to generate a power spectrum P, and outputs the generated power spectrum P to the absolute / logarithmic conversion unit 50. For example, the frequencies in the power spectrum P generated by the FFT processing unit 40 correspond to the distance between the radar device 300 and the target.

[0079] The absolute / logarithmic conversion unit 50 performs a logarithmic conversion on the power spectrum PA, which represents the absolute value of the power spectrum P received from the FFT processing unit 40, thereby generating echo data and outputting the generated echo data to the display processing unit 202.

[0080] <Interference Removal Section>

[0081] Figure 3 This is a diagram showing the structure of the interference removal unit in the signal processing unit according to an embodiment of the present invention. (Refer to...) Figure 3The 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 preprocessing 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), which includes a group of I signals Si(n) and Q signals Sq(n), from the A / D conversion unit 170.

[0082] 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 squares of the I signal Si(n) and the Q signal Sq(n) as the absolute value a(n), and outputs the calculated absolute value a(n) to the logarithmic detector unit 22.

[0083] The logarithmic detection unit 22 performs logarithmic detection on the absolute value 'a' received from the absolute value calculation unit 21, thereby calculating the logarithmic detection value B. 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.

[0084] The initial value calculation unit 23 calculates the average value AvB of the logarithmic detection values ​​B corresponding to the initial predetermined time during 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) during the sweep period T. Here, k is an integer greater than or equal to 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.

[0085] The filter unit 24 uses a smoothing filter to filter the signal based on the nth beat signal SD(n), i.e., the nth logarithmic detection value B(n), in the time region, thereby generating the nth filter signal A(n). In this invention, the filter signal is also called the smoothed signal. The filter unit 24 outputs the generated filter 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 infinite impulse response (IIR) filter, which is one type of digital filter.

[0086] For example, the filter unit 24 changes the setting of the smoothing filter based on the comparison result between the filter signal A(n-1) and the logarithmic detection value B(n) input to the smoothing filter. Specifically, the filter unit 24 changes the filtering formula as the setting of the smoothing filter.

[0087] More specifically, the filter unit 24 generates the filter signal A(n) according to the following formula (3) when the filter signal A(n-1) and the logarithmic detection value B(n) satisfy the following formula (1). On the other hand, the filter unit 24 generates the filter signal A(n) according to the following formula (4) when the filter signal A(n-1) and the logarithmic detection value B(n) satisfy the following formula (2). The specified threshold ThA in formulas (1) and (2) is a value preset to prevent the filter signal A(n) generated by the filter unit 24 from following the increase of the logarithmic detection value B(n) caused by the interference wave received by the receiving unit 150. Moreover, C in formula (3) is a specified coefficient with a value of zero or higher and less than 1.

[0088] B(n)-A(n-1)≦ThA…(1)

[0089] B(n)-A(n-1)>ThA…(2)

[0090] A(n)=B(n)×C+A(n-1)×(1-C)…(3)

[0091] A(n)=A(n-1)…(4)

[0092] Here, for example, the filter unit 24 determines the average value AvB of multiple logarithmic detection values ​​B(n) as the initial value of the filter signal A(n). More specifically, during each sweep period T, the filter unit 24 outputs the average value AvB received from the initial value calculation unit 23 as the initial value of the filter signal A(n) to the detection unit 25, regardless of equations (1) to (4).

[0093] For example, when the change in the logarithmic detector value B(n) input to the smoothing filter meets a predetermined condition, the filter unit 24 changes the setting of the smoothing filter to further suppress the time variation of the filter signal A(n). More specifically, when the change in the logarithmic detector value B(n) input to the smoothing filter is large and satisfies equation (2), the filter unit 24 sets the nth filter signal A(n) to the same value as the (n-1)th filter signal A(n-1), thereby suppressing the time variation of the filter signal A(n).

[0094] Figure 4This diagram illustrates an example of a beat signal received by the interference removal unit in the signal processing unit according to an embodiment of the present invention. Figure 4 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude. Figure 4 The solid line in the diagram represents the I signal Si(n) in the beat signal SD(n). Figure 4 The dashed line in the diagram represents the Q signal Sq(n) in the beat signal SD(n).

[0095] Figure 5 This diagram illustrates an example of the logarithmic detection value received by the filter unit in the interference removal unit of the signal processing unit according to an embodiment of the present invention, and the filter signal generated by the filter unit.

[0096] Figure 5 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude [dB]. Figure 5 The solid line in the diagram represents the filter signal A(n) generated by the filter section 24. Figure 5 The dashed line in the figure represents the logarithmic detection value B(n) received by the filter section 24.

[0097] Reference Figure 4 as well as Figure 5 Due to the influence of the interference wave, the amplitudes of the I signal Si(n) and the Q signal Sq(n) when the sampling number n is approximately 500 increase sharply. As a result, the level of the approximately 500th logarithmic detection value B(n) suddenly becomes a large value. The filter signal A(n) generated by the filter unit 24 follows the gradual change in the level of the logarithmic detection value B(n), but does not follow the sudden change in the level of the logarithmic detection value B(n).

[0098] The detection unit 25 detects the interference signal contained in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n).

[0099] For example, the detection unit 25 detects the interference signal based on the comparison result between the logarithmic detection value B(n) and the filter signal A(n). More specifically, the detection unit 25 detects the interference signal based on the difference or ratio between the logarithmic detection value B(n) and the filter signal A(n).

[0100] Specifically, the detection unit 25 determines that the beat signal SD(n) contains an interference signal if 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 equation (5). ThB in equation (5) is a predetermined threshold.

[0101] B(n)-A(n)≧ThB…(5)

[0102] Figure 6 This diagram illustrates an example of an interference determination mark generated by the detection unit in the interference removal unit of the signal processing unit according to an embodiment of the present invention. Figure 6 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD, and the vertical axis represents the marker value.

[0103] Reference Figure 6 The detection unit 25 generates an interference determination flag. In this interference determination flag, the flag value corresponding to the sampling number n of the beat signal SD(n) determined to contain an interference signal is 1, and the flag value corresponding to the sampling number n of the beat signal SD(n) not determined to contain an interference signal is zero. Specifically, the detection unit 25 generates an interference determination flag with a flag value of 1 when the sampling number n is approximately 500. The detection unit 25 outputs the generated interference determination flag to the correction unit 26.

[0104] The correction unit 26 performs signal processing to attenuate the amplitude of the interference signal, i.e., FFT preprocessing. More specifically, the correction unit 26 performs FFT preprocessing, that is, it receives the beat signal SD(n) from the A / D conversion unit 170 and attenuates the amplitude of the beat signal SD(n) in the received beat signal SD(n) where the mark value in the interference determination mark received from the detection unit 25 is 1. Hereinafter, the sample number n where the mark value in the interference determination mark is 1 is set as nx.

[0105] For example, the correction unit 26 replaces the amplitudes of the I signal Si(n) in the received beat signal SD(n) and the I signal Si(nx) and the Q signal Sq(nx) with the sampling number nx in the Q signal Sq(n) with zero as FFT preprocessing. The correction unit 26 outputs the FFT preprocessed beat signal SD(n) to the window function processing unit 30.

[0106] Refer again Figure 2 As described above, the window function processing unit 30 performs window function processing on the FFT-processed beat signal SD(n) received from the interference removal unit 20, and outputs the window function-processed beat signal SD(n) to the FFT processing unit 40. Furthermore, the FFT processing unit 40 performs FFT processing on the beat signal SD received from the window function processing unit 30, thereby generating a power spectrum.

[0107] Figure 7 This is a diagram showing an example of the power spectrum generated by the FFT processing unit in the signal processing unit of an embodiment of the present invention. Figure 7 In the diagram, the horizontal axis represents frequency, and the vertical axis represents amplitude [dB]. Figure 7 The dashed line in the figure represents an example of the power spectrum P1 generated by the FFT processing unit 40 after FFT preprocessing by the interference removal unit 20. Figure 7The solid line in the figure represents an example of the power spectrum P2 generated by the FFT processing unit 40 without FFT preprocessing.

[0108] Reference Figure 7 Without FFT preprocessing, the power spectrum P2 generated by the FFT processing unit 40 has a low signal-to-noise ratio (SN ratio) due to the interference wave. In contrast, with FFT preprocessing performed by the interference removal unit 20, the power spectrum P1 generated by the FFT processing unit 40 has a higher SN ratio than power spectrum P2, enabling more accurate detection of wave peaks. Therefore, targets in the target area can be detected accurately.

[0109] Furthermore, conventional pulse radar typically employs a method of detecting interference signals based on a comparison of signal levels in the azimuth direction of the received signal. Specifically, conventional pulse radar compares the signal levels of received signals in adjacent segmented target regions and determines that a received signal with an amplitude that is more pronounced than that in the adjacent segmented target regions contains an interference signal.

[0110] However, if the detection method used in pulse radar is applied to radar devices such as FM-CW, the power spectrum SN ratio may sometimes decrease. This will be explained in detail below.

[0111] Figure 8 as well as Figure 9 This is a diagram showing an example of the logarithmic detection values ​​generated in the radar device according to an embodiment of the present invention. Figure 9 yes Figure 8 A magnified view of region R1 in the image. Figure 8 as well as Figure 9 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude [dB]. Figure 8 as well as Figure 9 The solid line in the figure represents the logarithmic detection value B1(n) based on the beat signal SD1(n) corresponding to the segmented object region Ar1. Figure 8 as well as Figure 9 The dashed line in the figure represents the logarithmic detection value B2(n) based on the beat signal SD2(n) corresponding to the segmented object region Ar2 which is adjacent to the segmented object region Ar1. Figure 8 as well as Figure 9 A single chain line in the diagram represents the logarithmic detection value B3(n) based on the beat signal SD3(n) corresponding to the segmented object region Ar3, which is adjacent to the segmented object region Ar2.

[0112] Figure 8 In the logarithmic detector values ​​B1(n), B2(n), and B3(n), for example, the prominence of amplitudes exceeding 50 dB is caused by the influence of interference waves.

[0113] Reference Figure 9 Even when the amplitude of the logarithmic detector values ​​B1(n), B2(n), and B3(n) is below 50 dB and there is no interference wave, their amplitudes still differ. Therefore, in FM-CW radar devices, if interference signals are detected based on a comparison of the signal levels in the azimuth direction of the logarithmic detector value B, as in pulse radar, it may be mistakenly determined that the logarithmic detector value B, in the absence of interference waves, contains interference signals. Furthermore, if the mistakenly identified interference signals are removed, the signal-to-noise ratio (SN ratio) of the generated power spectrum may sometimes decrease.

[0114] In contrast, in the signal processing unit 100 of the embodiment of the present invention, the interference signal is detected based on the filter signal generated by filtering the logarithmic detector value B using a smoothing filter in the time region and the logarithmic detector value B. With this structure, compared with the structure that detects the interference signal based on the comparison result of the signal level in the azimuth direction of the logarithmic detector value B, the misjudgment of the interference signal can be suppressed, thereby detecting the interference signal more accurately. Therefore, the decrease in the SN ratio of the power spectrum P generated based on the beat signal SD can be suppressed.

[0115] [Variation Example]

[0116] Figure 10 This is a diagram showing the structure of the interference removal unit in a modified embodiment of the present disclosure. (Refer to...) Figure 10 Compared to the interference removal unit 20, the correction unit 26 is replaced by the correction unit 26A, and the window function generation unit 27 is also included. The signal processing unit 100 may also have a structure that replaces the interference removal unit 20 by including the interference removal unit 20A.

[0117] Figure 11 This is a diagram illustrating an example of a beat signal received by the interference removal unit in the signal processing unit of a modified embodiment of the present invention. Figure 11 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude. Figure 11 The solid line in the diagram represents the I signal Si(n) in the beat signal SD(n). Figure 11 The dashed line in the diagram represents the Q signal Sq(n) in the beat signal SD(n).

[0118] Reference Figure 11 Due to the influence of the interference wave, the amplitudes of the I signal Si(n) and Q signal Sq(n) when the sampling number n is approximately 100, and the I signal Si(n) and Q signal Sq(n) when the sampling number n is approximately 480, increase sharply.

[0119] Figure 12This diagram illustrates an example of an interference determination mark generated by the detection unit in the interference removal unit of the signal processing unit according to a modified embodiment of the present invention. Figure 12 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD, and the vertical axis represents the marker value.

[0120] Reference Figure 12 The detection unit 25 generates an interference determination flag with a flag value of 1 when the sampling number n is approximately 100 and a flag value of 1 when the sampling number n is approximately 480. The detection unit 25 outputs the generated interference determination flag to the window function generation unit 27.

[0121] The window function generation unit 27 receives the interference determination flag from the detection unit 25 and generates the window function Wf based on the received interference determination flag.

[0122] Figure 13 This is a diagram illustrating an example of a window function generated by the window function generation unit in the interference removal unit of the signal processing unit according to a modified embodiment of the present invention. Figure 13 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD, and the vertical axis represents the coefficient Wc of the window function.

[0123] Reference Figure 13 The window function generation unit 27 generates a window function Wf, in which the coefficient Wc of the sampling number nx when the value of the interference determination mark is 1 is zero, and as the sampling number n increases or decreases from nx, the coefficient Wc increases linearly and approaches 1. The window function generation unit 27 outputs the generated window function Wf to the correction unit 26A. Alternatively, the window function generation unit 27 may also be structured to generate a window function Wf in which the coefficient Wc increases curvilinearly, for example, like a sine curve, as the sampling number n increases or decreases from nx.

[0124] The correction unit 26A performs signal processing, namely FFT preprocessing, which attenuates the amplitude of the beat signal SD(n) in the region containing the interference signal by multiplying the beat signal SD(n) by a window function Wf. More specifically, the correction unit 26A performs window function processing as follows: it receives the beat signal SD(n) from the A / D conversion unit 170 and multiplies 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 window function-processed beat signal SD(n) to the window function processing unit 30.

[0125] Figure 14 as well as Figure 15 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of an embodiment of the present invention. Figure 15 yes Figure 14 A magnified view of region R2 in the image. Figure 14as well as Figure 15 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude. Figure 14 as well as Figure 15 The solid line in the middle represents the I signal Si(n) in the beat signal SD(n) after the FFT preprocessing performed by the correction unit 26. Figure 14 as well as Figure 15 The dashed line in the figure represents the Q signal Sq(n) in the beat signal SD(n) after the FFT preprocessing performed by the correction unit 26.

[0126] Figure 16 as well as Figure 17 This is a diagram illustrating an example of the beat signal after FFT preprocessing performed by the correction unit in the interference removal unit of a modified embodiment of the present invention. Figure 17 yes Figure 16 A magnified view of region R3 in the image. Figure 16 as well as Figure 17 In the diagram, the horizontal axis represents the sampling number n of the beat signal SD(n), and the vertical axis represents the amplitude. Figure 16 as well as Figure 17 The solid line in the middle represents the I signal Si(n) in the beat signal SD(n) after the FFT preprocessing performed by the correction unit 26A. Figure 16 as well as Figure 17 The dashed line in the figure represents the Q signal Sq(n) in the beat signal SD(n) after the FFT preprocessing performed by the correction unit 26A.

[0127] Reference Figure 15 as well as Figure 17 In the beat signal SD(n) after FFT preprocessing performed by correction unit 26, the amplitudes of the I signal Si(nx) and Q signal Sq(nx) of the sample number nx when the interference determination mark value is 1 are replaced with zero. As a result, the I signal Si(n) and Q signal Sq(n) of the sample number n before and after nx change drastically, i.e., they become discontinuities. In contrast, in the beat signal SD(n) after FFT preprocessing performed by correction unit 26A, the beat signal SD(n) is multiplied by the window function Wf. As a result, the amplitudes of the I signal Si(n) and Q signal Sq(n) of the sample number n before and after nx do not increase or decrease drastically, but change gradually, thus preventing discontinuities.

[0128] Figure 18 This is a diagram showing an example of the power spectrum generated by the FFT processing unit in the signal processing unit of an embodiment of the present invention. Figure 18 In the diagram, the horizontal axis represents frequency, and the vertical axis represents amplitude [dB]. Figure 18 The solid line in the figure represents the power spectrum P3 generated by the FFT processing unit 40 after FFT preprocessing by the interference removal unit 20. Figure 18The dashed line in the figure represents the power spectrum P4 generated by the FFT processing unit 40 when the FFT preprocessing is performed by the interference removal unit 20A in the modified example.

[0129] Reference Figure 18 The power spectrum P4 is generated based on the beat signal SD(n) without discontinuities, and therefore has a smaller range sidelobe compared to the power spectrum P3.

[0130] [Action Flow]

[0131] The radar device according to an embodiment of the present invention includes a computer containing a memory. The computer's central processing unit (CPU) and other arithmetic processing units read some or all of the steps of the following flowchart and sequence from the memory and execute them. The program can be installed externally. The program is distributed in a state stored on a recording medium.

[0132] Figure 19 This is a flowchart that specifies an example of the operation flow when performing FFT preprocessing on a radar device according to an embodiment of the present invention.

[0133] Reference Figure 19 First, the radar device 300 calculates the absolute value a(n) of the beat signal SD(n) (step S102).

[0134] Next, the radar device 300 performs logarithmic detection of the absolute value a(n) to calculate the logarithmic detection value B(n) (step S104).

[0135] Next, the radar device 300 uses a smoothing filter to filter the logarithmic detection value B(n) in the time region to generate the filter signal A(n) (step S106).

[0136] Next, the radar device 300 detects the interference signal contained in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n) (step S108).

[0137] Next, the radar device 300 performs FFT preprocessing to attenuate the amplitude of the interference signal (step S110).

[0138] Furthermore, the signal processing unit 100 in the embodiment of the present invention employs a structure including the correction unit 26, but is not limited thereto. The signal processing unit 100 may also be a structure that does not include the correction unit 26. In this case, for example, the signal processing unit 100 includes a notification unit that notifies an external part of the signal processing unit 100 of the detection result of the detection unit 25 of the interference signal.

[0139] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the filter unit 24 adopts a structure that determines the average value AvB of a plurality of logarithmic detection values ​​B(n) as the initial value of the filter signal A(n), but is not limited to this. The filter unit 24 may also be a structure that determines a preset value as the initial value of the filter signal A(n).

[0140] Furthermore, a technology is desired that can more accurately detect targets based on beat signals.

[0141] For example, the technology described in Patent Document 1 determines whether an interference wave is mixed into the radar received signal based on the absolute value of the time derivative of the amplitude of the radar received signal. This technology, as described in Patent Document 1, is difficult to detect, for example, low-frequency interference waves and interference waves with fixed frequencies. Furthermore, the technology described in Patent Document 2 requires processing such as Fourier transforms to detect interference waves, which leads to a larger circuit size.

[0142] In contrast, in the signal processing unit 100 of this embodiment, the filter unit 24 uses a smoothing filter to filter the logarithmic detection value B(n) of the beat signal SD(n) based on the transmitted signal and the received signal in the time region, thereby generating a filter signal A(n). The detection unit 25 detects the interference signal contained in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n).

[0143] Thus, by detecting the interference signal based on the filter signal A(n) generated by filtering the logarithmic detection value B(n) using a smoothing filter in the time region and the logarithmic detection value B(n), this structure allows for the detection of interference signals containing interference waves of multiple frequencies using simple processing. Furthermore, the signal level variation in the azimuth direction of the beat signal SD(n) is relatively large. Therefore, when applying the azimuth interference removal processing commonly used in conventional pulse radar to the beat signal SD(n), misjudgments of the interference signal can sometimes occur. In contrast, with the aforementioned structure, misjudgments caused by the azimuth signal level variation of the beat signal can be suppressed, thereby enabling more accurate detection of the interference signal. This also suppresses the decrease in the SN ratio of the power spectrum P generated based on the beat signal SD(n). Therefore, targets can be detected more accurately based on the beat signal SD(n).

[0144] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the filter unit 24 changes the setting of the smoothing filter based on the comparison result of the filter signal A(n-1) and the logarithmic detection value B(n).

[0145] With this structure, a filter signal A(n) that can more reliably detect interference signals can be generated based on the comparison result between the filter signal A(n-1) and the logarithmic detection value B(n).

[0146] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the filter unit 24 changes the smoothing filter to a setting that further suppresses the time variation of the filter signal A(n) when the change of the logarithmic detector value B(n) input to the smoothing filter meets a predetermined condition.

[0147] This structure can suppress the omission of interference signal detection caused by the filter signal A(n) following the change of the logarithmic detector value B(n), and can generate a filter signal A(n) that can more reliably detect interference signals.

[0148] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the detection unit 25 detects the interference signal based on the comparison result of the logarithmic detection value B(n) and the filter signal A(n).

[0149] With this structure, interference signals can be detected by using a simple process that combines the generated filter signal A(n) with the logarithmic detection value B(n).

[0150] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the detection unit 25 detects the interference signal based on the difference or ratio between the logarithmic detection value B(n) and the filter signal A(n).

[0151] With this structure, interference signals can be detected more accurately with simple processing by using the difference or ratio between the root filter signal A(n) and the logarithmic detector value B(n).

[0152] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the correction unit 26 performs signal processing to attenuate the amplitude of the interference signal.

[0153] This structure allows for the attenuation of the interference wave component in the beat signal SD(n), thus enabling the use of the corrected beat signal SD(n) to more accurately detect targets.

[0154] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the correction unit 26A performs signal processing to attenuate the amplitude of the beat signal SD(n) in the region containing the interference signal by multiplying the beat signal SD(n) by the window function Wf.

[0155] With this structure, the abrupt increase or decrease in amplitude in the modified beat signal SD(n) can be suppressed, thus suppressing the increase in range sidelobes in the power spectrum P generated by FFT processing of the beat signal SD(n).

[0156] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the filter unit 24 determines the average value AvB of the logarithmic detection value B(n) within a specified time as the initial value of the filter signal A(n).

[0157] With this structure, the filter signal A(n) can be generated using the determined initial values ​​and recursive functions.

[0158] Furthermore, in the signal processing unit 100 of the embodiment of the present invention, the smoothing filter used in the filter unit 24 is an IIR filter.

[0159] With this structure, compared to the structure that uses an FIR filter to generate the filter signal A(n), it is possible to generate a filter signal A(n) that increases or decreases rapidly relative to the logarithmic detector value B(n) without following it, thus suppressing false detection of the interference signal.

[0160] Furthermore, the radar device 300 according to an 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 the reflected signal, i.e., the signal reflected by the target, of the transmitted transmission signal.

[0161] With this structure, a radar device 300 can be realized that can detect targets more accurately based on beat signal SD(n) and logarithmic detection value B(n).

[0162] Furthermore, in the radar device 300 of the embodiment of the present invention, the transmitting unit 120 transmits a transmission signal via a rotating transmitting antenna 130, and the receiving unit 150 receives a reflected signal via a rotating receiving antenna 140.

[0163] This structure allows for the transmission of signals in all directions and the reception of reflected signals, thus enabling the detection of targets over a wider range.

[0164] Furthermore, the radar signal processing method of the present invention is used in the signal processing unit 100 of the radar device 300. In this radar signal processing method, firstly, a smoothing filter is used to filter the logarithmic detection value B(n) of the beat signal SD(n) based on the transmitted signal and the received signal in the time region, thereby generating a filter signal A(n). Next, the signal processing unit 100 detects the interference signal contained in the beat signal SD(n) based on the logarithmic detection value B(n) and the filter signal A(n).

[0165] Thus, by detecting the interference signal based on the filter signal A(n) generated by filtering the logarithmic detection value B(n) using a smoothing filter in the time region and the logarithmic detection value B(n), this method allows for the detection of interference signals containing interference waves of multiple frequencies using simple processing. Furthermore, the signal level variation in the azimuth direction of the beat signal SD(n) is relatively large. Therefore, when applying the azimuth interference removal processing commonly used in conventional pulse radar to the beat signal, misjudgment of the interference signal can sometimes occur. In contrast, the method described above can suppress misjudgment caused by the azimuth signal level variation of the beat signal SD(n), thereby enabling more accurate detection of the interference signal and suppressing the decrease in the SN ratio of the power spectrum P generated based on the beat signal SD(n). Therefore, targets can be detected more accurately based on the beat signal SD(n).

[0166] It should be considered that the embodiments described are illustrative and not restrictive in all respects. The scope of the invention is shown by the claims rather than the description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A radar signal processing device, comprising: The filter unit is configured to generate a processing signal based on the beat signal obtained from the transmitted signal and the received signal, and to generate a smooth signal by filtering the processing signal using a smoothing filter in the time region. as well as The detection unit is configured to detect interference signals contained in the beat signal based on the processed signal and the smoothed signal. The filter unit is configured to change the settings of the smoothing filter based on a comparison between the smoothed signal and the processed signal.

2. The radar signal processing apparatus according to claim 1, wherein... The smoothing filter is an infinite impulse response filter.

3. The radar signal processing apparatus according to claim 1, wherein... The filter unit is configured to change the setting of the smoothing filter to further suppress the time variation of the smoothed signal when the change of the processed signal meets the specified conditions.

4. The radar signal processing apparatus according to any one of claims 1 to 3, wherein The detection unit is configured to detect the interference signal based on a comparison between the processed signal and the smoothed signal.

5. The radar signal processing apparatus according to any one of claims 1 to 3, wherein The detection unit is configured to detect the interference signal based on the difference or ratio between the processed signal and the smoothed signal.

6. The radar signal processing apparatus according to any one of claims 1 to 3, wherein The radar signal processing device further includes: A correction unit is configured to attenuate the amplitude of the interference signal.

7. The radar signal processing apparatus according to claim 6, wherein... The correction unit is configured to attenuate the amplitude of the beat signal at the time containing the interference signal by applying a window function to the beat signal.

8. The radar signal processing apparatus according to any one of claims 1 to 3, wherein The filter section is configured to determine the average value of the processed signal over a specified time period as the initial value of the smoothed signal.

9. A radar device, comprising: Radar signal processing apparatus according to any one of claims 1 to 8; A transmitting unit configured to transmit the transmitted signal; as well as A receiving unit configured to receive the reflected signal reflected by the target.

10. The radar device according to claim 9, wherein The transmitting unit is configured to transmit the signal via a rotating antenna. The receiving unit is configured to receive the reflected signal via a rotating antenna.

11. A radar signal processing method, comprising: The processing signal is generated based on the beat signal obtained from the transmitted and received signals; A smoothed signal is generated by filtering the processed signal using a smoothing filter in the time region; and The interference signal contained in the beat signal is detected based on the processed signal and the smoothed signal. The setting of the smoothing filter is changed based on the comparison between the smoothed signal and the processed signal.

12. A storage medium storing a radar signal processing program configured to perform the following processing: The processing signal is generated based on the beat signal obtained from the transmitted and received signals; A smoothed signal is generated by filtering the processed signal using a smoothing filter in the time region; and The interference signal contained in the beat signal is detected based on the processed signal and the smoothed signal. The setting of the smoothing filter is changed based on the comparison between the smoothed signal and the processed signal.

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