Radar-fixed target removal device and radar-fixed target removal program

Abstract

To perform complete cancellation of a fixing target and prevention of erroneous detection of a slow-speed moving target even when reflection intensity of the fixing target is higher concerning a radar technique for canceling the fixing target and detecting the moving target.SOLUTION: A radar fixing target cancellation device 2 includes: an own speed information acquisition section 21 for acquiring information of an own speed of a mobile body 1; a Doppler spectrum calculation section 22 for Fourier-transforming a result obtained by multiplying a radar reflection signal by a window function so as to calculate a Doppler spectrum; and a fixing target cancellation section 23 for canceling intensity of the Doppler spectrum in a Doppler bank of a reverse speed and adjacent Doppler banks when the intensity of the Doppler spectrum in the Doppler bank of the own speed and the reverse speed is higher than a predetermined threshold, and canceling a fixing target FT having a relative speed with respect to the mobile body 1 corresponding to the Doppler bank of the reverse speed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0004] , ,

[0006] , , , ,

[0005] , , , ,

[0001] The present disclosure relates to radar technology for removing fixed targets and detecting moving targets.

Background Art

[0002] Radar technology (Moving Target Indicator) for removing fixed targets and detecting moving targets is disclosed in Patent Document 1 etc. In Patent Document 1 etc., a Doppler spectrum is calculated using a solid-state radar or the like, and fixed targets are removed and moving targets are detected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A specific example of the prior art radar fixed target removal process is shown in FIG. 1. The moving body is equipped with a radar transceiver such as a solid-state radar device. The radar transceiver receives radar reflection signals. The following processes are executed within each cell (within each distance range and each azimuth range).

[0005] First, information on the self-speed of the moving body (the speed along the irradiation direction of the radar) is acquired. Next, the result of multiplying the radar reflection signal by a window function such as a Blackman window is Fourier-transformed to calculate the Doppler spectrum. Next, the intensity of the Doppler spectrum in the Doppler bank of the self-speed and the reverse speed (positive / 0 / negative speed according to the irradiation direction of the radar) is removed, and fixed targets having a relative speed with respect to the moving body corresponding to the Doppler bank of the reverse speed are removed.

[0006] Here, when the reflection intensity of a stationary target is high, the Doppler spectrum of the stationary target spreads not only to the Doppler bank of the reverse velocity but also to adjacent Doppler banks due to the effect of multiplying the radar reflection signal by a window function. Furthermore, even if the intensity of the Doppler spectrum in the Doppler bank of the reverse velocity is removed, the intensity of the Doppler spectrum in the adjacent Doppler bank remains above the minimum sensitivity intensity. Therefore, it is not possible to completely remove the stationary target, and it is not possible to prevent false detection of slow-moving targets.

[0007] Therefore, in order to solve the aforementioned problems, this disclosure aims to completely remove fixed targets even when the reflectivity of fixed targets is high, and to prevent false detection of slow-moving targets, in radar technology that removes fixed targets and detects moving targets. [Means for solving the problem]

[0008] To solve the aforementioned problem, when the intensity of the Doppler spectrum in the Doppler bank of the current velocity and the inverse velocity is higher than a predetermined threshold, the intensity of the Doppler spectrum is removed not only from the inverse velocity Doppler bank but also from adjacent Doppler banks.

[0009] Specifically, the present disclosure is a radar fixed target removal device characterized by comprising: a self-velocity information acquisition unit that acquires information on the self-velocity of a moving object equipped with a radar transceiver; a Doppler spectrum calculation unit that performs a Fourier transform on the result of multiplying the radar reflection signal received by the radar transceiver by a window function and calculates a Doppler spectrum; and a fixed target removal unit that, when the intensity of the Doppler spectrum in the Doppler bank for the self-velocity and the inverse velocity is higher than a predetermined threshold, removes the intensity of the Doppler spectrum in the inverse velocity Doppler bank and adjacent Doppler banks, and removes a fixed target having a relative velocity with respect to the moving object corresponding to the inverse velocity Doppler bank.

[0010] This configuration allows for the complete removal of stationary targets, even when their reflectivity is high, while also preventing the false detection of slow-moving targets.

[0011] Furthermore, this disclosure provides a radar fixed target removal device characterized in that the fixed target removal unit sets the intensity of the Doppler spectrum in the reverse velocity Doppler bank as the predetermined threshold, such that the intensity of the Doppler spectrum in the adjacent Doppler bank becomes equal to the minimum sensitivity intensity.

[0012] This configuration allows for the appropriate setting of the predetermined thresholds described above in order to completely eliminate stationary targets and prevent false detection of slow-moving targets.

[0013] Furthermore, this disclosure provides a radar fixed target removal device characterized in that the fixed target removal unit calculates the expected intensity of the Doppler spectrum for the Doppler spectrum in the adjacent Doppler bank based on the intensity of the Doppler spectrum in the reverse velocity Doppler bank and the spread of the Doppler spectrum due to the effect of multiplying the radar reflection signal by the window function, and when the intensity of the Doppler spectrum in the adjacent Doppler bank is higher than the expected intensity of the Doppler spectrum by a predetermined dB or more, the intensity of the Doppler spectrum in the adjacent Doppler bank is excluded from the removal target, and a moving target having a relative velocity with respect to the moving object corresponding to the adjacent Doppler bank is detected.

[0014] This configuration makes it possible to prevent the false removal of slow-moving targets based on the broadening of the Doppler spectrum when slow-moving targets are actually present.

[0015] Furthermore, this disclosure provides a radar fixed target removal device characterized in that, when the intensity of the Doppler spectrum in the adjacent Doppler bank on one side of the reverse velocity Doppler bank is higher by a predetermined dB or more than the intensity of the Doppler spectrum in the adjacent Doppler bank on the other side of the reverse velocity Doppler bank, the intensity of the Doppler spectrum in the adjacent Doppler bank on one side is excluded from the removal target, and a moving target having a relative velocity with respect to the moving object corresponding to the adjacent Doppler bank on one side is detected.

[0016] This configuration makes it possible to prevent the false removal of slow-moving targets based on the asymmetry of the Doppler spectrum when slow-moving targets are actually present.

[0017] Furthermore, this disclosure is a radar-fixed target removal program that causes a computer to execute each processing step performed by each processing unit of the radar-fixed target removal device described above.

[0018] This configuration makes it possible to provide a program that has the effects described above.

[0019] Furthermore, the inventions disclosed above can be combined as much as possible. [Effects of the Invention]

[0020] Thus, this disclosure provides radar technology for removing stationary targets and detecting moving targets, which can completely remove stationary targets even when the reflectivity of the stationary targets is high, and can also prevent false detection of slow-moving targets. [Brief explanation of the drawing]

[0021] [Figure 1] This figure shows a specific example of conventional radar target removal processing. [Figure 2] This figure shows the configuration of the radar-based target removal device described herein. [Figure 3] It is a diagram showing the procedure of the radar fixed target removal process of the present disclosure. [Figure 4] It is a diagram showing a specific example of the radar fixed target removal process of the present disclosure. [Figure 5] It is a diagram showing a predetermined threshold value of the radar fixed target removal process of the present disclosure. [Figure 6] It is a diagram showing a specific example of the radar moving target detection process of the present disclosure. [Figure 7] It is a diagram showing a specific example of the radar moving target detection process of the present disclosure.

Embodiments for Carrying Out the Invention

[0022] Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementing the present disclosure, and the present disclosure is not limited to the following embodiments.

[0023] (Configuration of the Radar Fixed Target Removal Device of the Present Disclosure) The configuration of the radar fixed target removal device of the present disclosure is shown in FIG. 2. The moving body 1 is equipped with a GPS sensor 11 or a gyro sensor 11 and a radar transceiver device 12 such as a solid-state radar device. The GPS sensor 11 or the gyro sensor 11 outputs information on the self-speed (speed in Earth coordinates, etc.) of the moving body 1. The radar transceiver device 12 receives a radar reflection signal.

[0024] [[ID=3l]]The procedure of the radar fixed target removal process of the present disclosure is shown in FIG. 3. The radar fixed target removal device 2 includes a self-speed information acquisition unit 21, a Doppler spectrum calculation unit 22, and a fixed target removal unit 23. The radar fixed target removal device 2 may install the program shown in FIG. 3 in a computer, or may execute the processing procedure shown in FIG. 3 on an FPGA.

[0025] First, as a general rule, the process of completely eliminating fixed targets (FT) and preventing false detection of slow-moving targets (MT) will be explained using Figures 3, 4, and 5. Next, as an exception, the process of preventing false removal of slow-moving targets (MT) when they are actually present will be explained using Figures 3, 6, and 7. These general and exceptional processes are executed within each cell (within each distance range and each azimuth range).

[0026] (Specific example of radar target removal processing in this disclosure) A specific example of the radar fixed target removal process of this disclosure is shown in Figure 4. The self-velocity information acquisition unit 21 acquires information on the self-velocity of the moving object 1 (velocity along the direction of radar irradiation) (step S1). The Doppler spectrum calculation unit 22 calculates the Doppler spectrum by performing a Fourier transform on the result of multiplying the radar reflection signal by a window function such as a Blackman window (step S2).

[0027] In the upper left column of Figure 4, when the reflection intensity of the fixed target FT is high, the Doppler spectrum of the fixed target FT spreads not only to the Doppler banks of its own velocity and inverse velocity (positive / 0 / negative velocity depending on the direction of radar illumination) but also to adjacent Doppler banks (which may be separated by only one bank or by two or more banks). As a result, the intensity of the Doppler spectrum in the inverse velocity Doppler bank exceeds the minimum sensitivity intensity, and the intensity of the Doppler spectrum in the adjacent Doppler bank also exceeds the minimum sensitivity intensity. Consequently, the intensity of the Doppler spectrum in the inverse velocity Doppler bank becomes higher than the predetermined threshold shown in Figure 5 (Step S3, YES).

[0028] In the lower left section of Figure 4, the fixed target removal unit 23 removes the intensity of the Doppler spectrum in the reverse-velocity Doppler bank, as well as the intensity of the Doppler spectrum in the adjacent Doppler bank, thereby removing the fixed target FT which has a relative velocity to the moving object 1 corresponding to the reverse-velocity Doppler bank (step S4). Therefore, the fixed target removal unit 23 can completely remove the fixed target FT even when the reflection intensity of the fixed target FT is high, and can also prevent false detection of slow-moving targets MT.

[0029] In the upper right column of Figure 4, when the reflection intensity of the fixed target FT is low, there is no effect from the window function multiplying the radar reflection signal, and the Doppler spectrum of the fixed target FT extends only to the Doppler banks of its own velocity and inverse velocity (positive / 0 / negative velocity depending on the direction of radar illumination), and does not spread to adjacent Doppler banks (which may be separated by only one bank or by two or more banks). Furthermore, although the intensity of the Doppler spectrum in the inverse velocity Doppler bank exceeds the minimum sensitivity intensity, the intensity of the Doppler spectrum in adjacent Doppler banks does not exceed the minimum sensitivity intensity. Consequently, the intensity of the Doppler spectrum in the inverse velocity Doppler bank becomes lower than the predetermined threshold shown in Figure 5 (Step S3, NO).

[0030] In the lower right section of Figure 4, the fixed target removal unit 23 removes the intensity of the Doppler spectrum in the reverse-velocity Doppler bank, but maintains the intensity of the Doppler spectrum in the adjacent Doppler bank, thereby removing the fixed target FT which has a relative velocity to the moving body 1 corresponding to the reverse-velocity Doppler bank (step S5). Therefore, when the reflection intensity of the fixed target FT is low, the fixed target removal unit 23 can completely remove the fixed target FT, similar to a conventional Moving Target Indicator.

[0031] Figure 5 shows the predetermined threshold for the radar fixed target removal process of this disclosure. The fixed target removal unit 23 sets the intensity of the Doppler spectrum in the inverse velocity Doppler bank as a predetermined threshold such that the intensity of the Doppler spectrum in the adjacent Doppler bank is equal to the minimum sensitivity intensity (step S3). Specifically, the radar reflection signal having frequencies and various amplitudes corresponding to the inverse velocity is multiplied by a window function such as a Blackman window, and the result is Fourier transformed to calculate the Doppler spectrum of the inverse velocity Doppler bank having various intensities. Then, the intensity of the inverse velocity Doppler bank is selected such that the intensity of the adjacent Doppler bank is equal to the minimum sensitivity intensity, and the selected intensity is set as the predetermined threshold.

[0032] Therefore, the fixed target removal unit 23 can appropriately set predetermined thresholds shown in the upper left and upper right columns of Figure 4 in order to completely remove the fixed target FT and prevent false detection of slow-moving targets MT. In other words, the fixed target removal unit 23 can appropriately execute the processes shown in the upper left and lower left columns of Figure 4 or the processes shown in the upper right and lower right columns of Figure 4.

[0033] (Specific example of radar moving target detection processing in this disclosure) A specific example of the radar moving target detection process of this disclosure is shown in Figure 6. In Figure 6, when a slow-moving target MT is actually present, the following process is performed based on the spread of the Doppler spectrum to prevent the false removal of the slow-moving target MT.

[0034] The fixed target removal unit 23 calculates the expected intensity of the Doppler spectrum for adjacent Doppler banks based on the intensity of the Doppler spectrum in the reverse velocity Doppler bank and the broadening of the Doppler spectrum due to the effect of multiplying the radar reflection signal by a window function (step S6).

[0035] Specifically, similar to Figure 5, the radar reflection signals, which have frequencies and amplitudes corresponding to the inverse velocity, are multiplied by a window function such as the Blackman window, and the resulting Fourier transform is performed to calculate Doppler spectra with various intensities of the inverse velocity Doppler bank. Then, in Figure 6, the intensities of adjacent Doppler banks are selected such that the intensity of the inverse velocity Doppler bank is equal to the observed intensity, and the selected intensity is calculated as the expected intensity.

[0036] In the upper left column of Figure 6, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the reverse velocity Doppler bank is higher than the predetermined threshold shown in Figure 5 (Step S3, YES). However, unlike the upper left column of Figure 4, the intensity of the Doppler spectrum in the adjacent Doppler bank (which may be on the low-velocity side, the high-velocity side, or both sides) is higher than the expected intensity of the Doppler spectrum by a predetermined dB or more (Step S6, YES). In other words, it is considered highly likely that a slow-moving target MT actually exists.

[0037] In the lower left section of Figure 6, similar to the lower left section of Figure 4, the fixed target removal unit 23 removes fixed targets FT that have a relative velocity to the moving object 1 corresponding to the reverse velocity Doppler bank (step S4). However, unlike the lower left section of Figure 4, the fixed target removal unit 23 excludes the intensity of the Doppler spectrum in adjacent Doppler banks (which may be on the low-speed side, the high-speed side, or both sides) from the removal target and detects moving targets MT that have a relative velocity to the moving object 1 corresponding to the adjacent Doppler bank (step S7). Therefore, when slow-moving targets MT actually exist, the fixed target removal unit 23 can prevent the erroneous removal of slow-moving targets MT based on the spread of the Doppler spectrum.

[0038] In the upper right column of Figure 6, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the reverse velocity Doppler bank is higher than the predetermined threshold shown in Figure 5 (Step S3, YES). Furthermore, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the adjacent Doppler bank (which may be on the low-velocity side, the high-velocity side, or both sides) does not become higher than the expected intensity of the Doppler spectrum by more than a predetermined dB (Step S6, NO). In other words, it is considered unlikely that a slow-moving target MT actually exists.

[0039] In the lower right section of Figure 6, similar to the lower left section of Figure 4, the fixed target removal unit 23 removes fixed targets FT that have a relative velocity to the moving object 1 corresponding to the reverse velocity Doppler bank (step S4). Then, similar to the lower left section of Figure 4, the fixed target removal unit 23 does not exclude the intensity of the Doppler spectrum in adjacent Doppler banks (which may be on the low-speed side, the high-speed side, or both sides) from the removal target, and does not detect moving targets MT that have a relative velocity to the moving object 1 corresponding to the adjacent Doppler bank (step S4). Therefore, when slow-moving targets MT do not actually exist, the fixed target removal unit 23 can prevent false detection of slow-moving targets MT based on the spread of the Doppler spectrum.

[0040] A specific example of the radar moving target detection process of this disclosure is also shown in Figure 7. In Figure 7, when a slow-moving target MT is actually present, the following process is performed based on the asymmetry of the Doppler spectrum to prevent the false removal of the slow-moving target MT.

[0041] In the upper left column of Figure 7, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the reverse-velocity Doppler bank is higher than the predetermined threshold shown in Figure 5 (Step S3, YES). However, unlike the upper left column of Figure 4, the intensity of the Doppler spectrum in the adjacent Doppler bank on one side of the reverse-velocity Doppler bank (which may be on the low-velocity or high-velocity side) is higher than the intensity of the Doppler spectrum in the adjacent Doppler bank on the other side of the reverse-velocity Doppler bank by a predetermined dB or more (Step S8, YES). In other words, it is considered highly likely that a slow-moving target MT actually exists.

[0042] In the lower left column of Figure 7, similar to the lower left column of Figure 4, the fixed target removal unit 23 removes fixed targets FT that have a relative velocity to the moving body 1 corresponding to the reverse velocity Doppler bank (step S4). However, unlike the lower left column of Figure 4, the fixed target removal unit 23 excludes the intensity of the Doppler spectrum in an adjacent Doppler bank on one side (which may be on the low-speed or high-speed side) from the removal target and detects moving targets MT that have a relative velocity to the moving body 1 corresponding to an adjacent Doppler bank on one side (step S9). Therefore, when slow-moving targets MT actually exist, the fixed target removal unit 23 can prevent the erroneous removal of slow-moving targets MT based on the asymmetry of the Doppler spectrum.

[0043] In the upper right column of Figure 7, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the reverse-velocity Doppler bank is higher than the predetermined threshold shown in Figure 5 (Step S3, YES). Furthermore, similar to the upper left column of Figure 4, the intensity of the Doppler spectrum in the adjacent Doppler bank on one side of the reverse-velocity Doppler bank (which may be on the low-velocity or high-velocity side) does not exceed a predetermined dB compared to the intensity of the Doppler spectrum in the adjacent Doppler bank on the other side of the reverse-velocity Doppler bank (Step S8, NO). In other words, it is considered unlikely that a slow-moving target MT actually exists.

[0044] In the lower right section of Figure 7, similar to the lower left section of Figure 4, the fixed target removal unit 23 removes the fixed target FT that has a relative velocity to the moving object 1 corresponding to the reverse velocity Doppler bank (step S4). Then, similar to the lower left section of Figure 4, the fixed target removal unit 23 does not exclude the intensity of the Doppler spectrum in the adjacent Doppler bank on one side (which may be on the low-speed or high-speed side) from the removal target, and does not detect the moving target MT that has a relative velocity to the moving object 1 corresponding to the adjacent Doppler bank on one side (step S4). Therefore, the fixed target removal unit 23 can prevent false detection of slow-moving targets MT based on the symmetry of the Doppler spectrum when slow-moving targets MT do not actually exist. [Industrial applicability]

[0045] The radar fixed target removal device and radar fixed target removal program of this disclosure are radar technologies that remove fixed targets and detect moving targets, and can completely remove fixed targets even when the reflectivity of the fixed targets is high, while also preventing false detection of slow-moving targets. [Explanation of Symbols]

[0046] FT: Fixed target MT: Moving target 1: Mobile 2: Radar-based target removal device 11: GPS sensor 11: Gyro sensor 12: Radar Transceiver 21: Own speed information acquisition part 22: Doppler spectrum calculation unit 23: Fixed target removal section

Claims

1. A vehicle speed information acquisition unit that acquires vehicle speed information of a mobile vehicle equipped with a radar transceiver, A Doppler spectrum calculation unit calculates a Doppler spectrum by performing a Fourier transform on the result of multiplying the radar reflection signal received by the radar transceiver by a window function, A fixed target removal unit removes the intensity of the Doppler spectrum in the Doppler bank of the self-velocity and the Doppler bank of the reverse velocity when the intensity of the Doppler spectrum in the reverse velocity Doppler bank and adjacent Doppler banks is higher than a predetermined threshold, and removes a fixed target having a relative velocity with respect to the moving body corresponding to the reverse velocity Doppler bank. A radar-based target removal device characterized by comprising the following features.

2. The fixed target removal unit sets the intensity of the Doppler spectrum in the reverse velocity Doppler bank as the predetermined threshold such that the intensity of the Doppler spectrum in the adjacent Doppler bank becomes equal to the minimum sensitivity intensity. A radar-fixed target removal device according to claim 1, characterized in that...

3. The fixed target removal unit calculates the expected intensity of the Doppler spectrum for the Doppler spectrum in the adjacent Doppler bank based on the intensity of the Doppler spectrum in the reverse velocity Doppler bank and the broadening of the Doppler spectrum due to the effect of multiplying the radar reflection signal by the window function. When the intensity of the Doppler spectrum in the adjacent Doppler bank is higher than the expected intensity of the Doppler spectrum by a predetermined dB or more, the intensity of the Doppler spectrum in the adjacent Doppler bank is excluded from the removal target, and a moving target having a relative velocity with respect to the moving object corresponding to the adjacent Doppler bank is detected. A radar-fixed target removal device according to claim 1 or 2, characterized in that...

4. The fixed target removal unit, when the intensity of the Doppler spectrum in the adjacent Doppler bank on one side of the reverse velocity Doppler bank is higher by a predetermined dB or more than the intensity of the Doppler spectrum in the adjacent Doppler bank on the other side of the reverse velocity Doppler bank, removes the intensity of the Doppler spectrum in the adjacent Doppler bank on one side from the removal target and detects a moving target having a relative velocity with respect to the moving object corresponding to the adjacent Doppler bank on one side. A radar-fixed target removal device according to claim 1 or 2, characterized in that...

5. A radar-fixed target removal program for causing a computer to perform each processing step performed by each processing unit of the radar-fixed target removal device according to claim 1 or 2.

Images