A UWB radar moving target detection and positioning method

Abstract

The present invention provides a UWB radar moving target detection and positioning method, the method comprising: performing FIR bandpass filtering on the original signal to obtain a first signal; performing FFT on the real and imaginary signals of the first signal on all range gates and calculating the peak-to-average ratio of the results; if the peak-to-average ratio is greater than a first threshold value, it is determined that a moving signal may have appeared; selecting a time domain signal with a preset window length on the range gate, equalizing the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; calculating the direction by DOA; taking the real or imaginary part of the second signal, performing Hilbert transform and constructing a third signal; obtaining the signal modulus value of the third signal, when the signal modulus value is greater than the second threshold value, it is determined that a moving signal has appeared, and the first range gate where the signal appears is the target range gate. The UWB radar moving target detection and positioning method provided by the present invention improves the detection success rate and reliability.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-wideband technology, and in particular to a UWB radar moving target detection and positioning method. Background Art

[0002] Since the performance indicators of UWB (Ultra Wide Band) radar, such as the number of antennas, time resolution, and phase resolution, are significantly different from those of millimeter-wave radar or lidar, UWB radar is usually used in scenarios related to moving targets based on the Doppler effect.

[0003] The original signal of UWB radar contains various interferences such as random noise, DC, clutter, etc. It is often difficult to obtain accurate Doppler information through FFT (Fast Fourier Transform) without processing; the receiver also has the problem of IQ imbalance, that is, the signal amplitude of the real part and imaginary part of CIR (Channel Impulse Response) are not consistent, resulting in the inclusion of noise components in the obtained signal phase, affecting the accuracy of azimuth detection. In addition, the real-time performance of large-scale FFT target detection is poor and the calculation overhead is high; the probability of false alarm and missed detection of small-scale FFT detection is relatively high, and the reliability is poor.

[0004] Therefore, it is necessary to provide a UWB radar moving target detection and positioning method to effectively solve the above problems. Summary of the invention

[0005] In view of the problems and shortcomings of the prior art, the present invention provides a UWB radar moving target detection and positioning method, which effectively suppresses the clutter, DC and high-frequency noise components in the radar signal by performing bandpass filtering on the original CIR signal of the UWB radar system, and effectively eliminates the phase noise of the signal by time domain sliding equalization and Hilbert transform, thereby further improving the detection success rate and the reliability of radar ranging and direction finding.

[0006] An embodiment of the present invention provides a UWB radar moving target detection and positioning method, the method comprising: Performing FIR bandpass filtering on the original signal to obtain a first signal; Performing FFT on the real and imaginary signals of the first signal at all range gates respectively and calculating the peak-to-average ratio of the results; If the peak-to-average ratio is greater than a first threshold value, it is determined that a motion signal may have occurred; Select a time domain signal with a preset window length on the range gate, and equalize the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; Calculate direction through DOA; Taking the real part or the imaginary part of the second signal, performing Hilbert transform on the second signal, and constructing a third signal; Calculating a signal modulus value for the third signal, and when the signal modulus value is greater than a second threshold value, it is determined that a motion signal has appeared, and the first range gate where the signal appears is the target range gate; The position of the moving target is calculated according to the target range gate and the direction.

[0007] Preferably, if the peak-to-average ratio is greater than the first threshold value, the frequency point corresponding to the FFT peak is recorded, and the frequency point is the Doppler frequency shift caused by the target movement. The movement speed of the target is obtained according to the Doppler frequency shift, which is specifically calculated by the following formula:

[0008] in, represents the radial velocity of the target relative to the radar, Indicates the center frequency of the UWB radar pulse, represents the speed of light, Indicates the Doppler frequency deviation.

[0009] Preferably, the selection of the time domain signal with a preset window length on the range gate includes selecting a sliding window for statistics, wherein the sliding step is less than 1 / 2 of the preset window length, and when sliding, the maximum and minimum values ​​of the real and imaginary parts of the first signal are recorded respectively, and the range is calculated and cached.

[0010] Preferably, after the window no longer contains the approximate sine wave caused by the Doppler effect, statistics are stopped and the mean of the range is calculated, as well as the equalization coefficient by which the imaginary part should be scaled. The equalization coefficient is calculated by the following formula:

[0011] in, and Take the real and imaginary parts respectively.

[0012] Preferably, the second signal is calculated by the following formula:

[0013] in, Indicates the second signal, Indicates the first signal.

[0014] Preferably, when the UWB radar system includes a transmitting antenna and two receiving antennas, a first phase difference from the target to two receiving channels is calculated based on the motion signal, and a second phase difference of the two receiving channels is obtained after compensation, thereby obtaining the incident angle of the echo signal.

[0015] Preferably, the first phase difference is calculated by the following formula:

[0016] in, and Represent the complex signals of the two channels respectively, and Represent the amplitudes of the two signals respectively. and They represent the phases of the two echo signals arriving at the receiver, and the two signals are conjugated and multiplied to obtain .

[0017] Preferably, the second phase difference is calculated by the following formula:

[0018] in, To calculate the remainder, Indicates the fixed phase compensation value between receiving channels.

[0019] Preferably, the echo signal incident angle is calculated by the following formula:

[0020] in, represents the incident angle of the echo signal, represents the wavelength, Indicates the center frequency of the UWB radar pulse, Represents the speed of light.

[0021] Preferably, the real part or the imaginary part of the second signal is taken ,but

[0022] Performing Hilbert transform gives constructing the third signal,

[0023] in, is the Cauchy principal value integral, which is used to deal with singular points in the integral. Indicates the third signal.

[0024] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects: An embodiment of the present invention provides a UWB radar moving target detection and positioning method, the method comprising: performing FIR bandpass filtering on an original signal to obtain a first signal; performing FFT on the real and imaginary signals of the first signal on all range gates and calculating the peak-to-average ratio of the results; if the peak-to-average ratio is greater than a first threshold value, it is determined that a moving signal may have appeared; selecting a time domain signal with a preset window length on the range gate, and equalizing the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; calculating the direction through DOA; taking the real or imaginary part of the second signal, and performing Hill After the Hilbert transform, a third signal is constructed; a signal modulus value is calculated for the third signal, and when the signal modulus value is greater than a second threshold value, it is determined that a motion signal has appeared, and the first range gate where the signal appears is the target range gate; the position of the moving target is calculated according to the target range gate and the direction; the clutter, DC and high-frequency noise components in the radar signal are effectively suppressed by performing bandpass filtering on the original CIR signal of the UWB radar system; the phase noise of the signal is effectively eliminated by time domain sliding equalization and Hilbert transform, which further improves the detection success rate and the reliability of radar ranging and direction finding; Furthermore, a real-time positioning method with good effect and low overhead is provided for UWB radar positioning; Furthermore, the method is cleverly designed, simple to implement, and has reliable ranging and direction finding detection accuracy, providing a feasible positioning method for low-cost UWB radars with high market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present invention, not all embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0026] Figure 1 A schematic diagram of a flow chart of a UWB radar moving target detection and positioning method according to a preferred embodiment of the present invention; Figure 2 A UWB radar moving target detection and positioning method according to a preferred embodiment of the present invention includes a CIR time domain original signal diagram of a moving target; Figure 3 A time domain filtered signal diagram after bandpass filtering of the original signal in a UWB radar moving target detection and positioning method in a preferred embodiment of the present invention; Figure 4 A time domain equalization signal diagram for equalizing a filtered signal in a UWB radar moving target detection and positioning method according to a preferred embodiment of the present invention; Figure 5 The present invention is a polar coordinate display diagram of the ranging, direction finding and positioning results of a moving target in a UWB radar moving target detection and positioning method in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0029] In view of the problems and shortcomings of the prior art, the present invention provides a UWB radar moving target detection and positioning method, which effectively suppresses the clutter, DC and high-frequency noise components in the radar signal by performing bandpass filtering on the original CIR signal of the UWB radar system, and effectively eliminates the phase noise of the signal by time domain sliding equalization and Hilbert transform, thereby further improving the detection success rate and the reliability of radar ranging and direction finding.

[0030] The present invention detects the distance of a moving target based on the amplitude-frequency response of the Fast Fourier Transform (FFT), extracts phase difference features based on the difference in angle of arrival (DOA) between different receiving channels to complete direction detection, and realizes a method for real-time positioning based on the distance and direction information of the moving target.

[0031] Figure 1 FIG. 1 is a flow chart of a UWB radar moving target detection and positioning method according to a preferred embodiment of the present invention. Figure 1 , a UWB radar moving target detection and positioning method, the method comprising: Step S101: performing FIR bandpass filtering on the original signal to obtain a first signal; Step S102: performing FFT on the real and imaginary signals of the first signal at all range gates respectively and calculating the peak-to-average ratio of the results; Step S103: if the peak-to-average ratio is greater than a first threshold value, it is determined that a motion signal may have occurred; Step S104: selecting a time domain signal with a preset window length on the range gate, and equalizing the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; Step S105: Calculate the direction through DOA; Step S106: taking the real part or the imaginary part of the second signal, performing Hilbert transform and constructing a third signal; Step S107: calculating a signal modulus value of the third signal. When the signal modulus value is greater than a second threshold value, it is determined that a motion signal has appeared, and the first range gate where the signal appears is the target range gate. Step S108: Calculate the position of the moving target according to the target range gate and the direction.

[0032] In step S101, taking the CIR original signal containing a moving target measured by the UWB radar as an example, it is expressed as , assuming the system radar sampling frequency , perform FIR bandpass filtering on the original signal, and express the CIR signal after bandpass filtering, that is, the first signal as .

[0033] The purpose of this step is to eliminate the high-frequency noise contained in the CIR and suppress clutter through a low-pass filter; remove the DC component of each range gate through a high-pass filter to eliminate the phase error caused by the different DC components of the real and imaginary parts of the complex signal. The cutoff frequency of the low-pass filter needs to be determined according to the upper speed limit of the target to be detected in the application scenario, and the high-pass filter can be selected around 1Hz.

[0034] Take the signal on the range gate where the moving target is located, and its time domain signals before and after filtering are as follows: Figure 2 and Figure 3 shown.

[0035] In step S102, it is assumed that the total number of range gates is , select the signal buffer window length , data processing interval points , that is, the first data processing needs to cache 10.24 seconds of data, and then update the data processing results every 0.64 seconds.

[0036] When the data processing conditions are met, the filtered signal in the buffer window, that is, the first signal Perform FFT on the real and imaginary signals at all range gates and calculate the peak-to-average ratio of the results.

[0037] In a specific implementation, if the peak-to-average ratio is greater than a first threshold value , record the frequency point corresponding to the FFT peak, which is the Doppler frequency deviation caused by the target movement , according to the Doppler frequency deviation The moving speed of the target is obtained, which is specifically calculated by the following formula:

[0038] in, represents the radial velocity of the target relative to the radar, Indicates the center frequency of the UWB radar pulse, represents the speed of light, Indicates Doppler frequency deviation. Since FFT is performed on a complex signal, the frequency shift It may be positive or negative. A positive number indicates that the target is moving towards the radar. A negative number means the target is moving away from the radar.

[0039] When the frequency domain detection determines that there is a motion signal, a time domain signal of a certain window length on the range gate is selected, which needs to cover at least one phase cycle, and the imaginary signal is balanced according to the peak-to-valley ratio of the real and imaginary signals in the window to achieve energy unity with the real signal. This step is performed after the frequency domain detection is completed. On the one hand, it can greatly reduce the computational overhead, and on the other hand, it can prevent the noise when there is no target from being amplified, thereby causing missed detection.

[0040] In a specific implementation, the selection of the time domain signal with a preset window length on the range gate includes selecting a sliding window for statistics, where the sliding step is less than 1 / 2 of the preset window length, and when sliding, the maximum and minimum values ​​of the real and imaginary parts of the first signal are recorded respectively, and the range is calculated and cached.

[0041] In a specific implementation, after the window no longer contains the approximate sine wave caused by the Doppler effect, statistics are stopped and the mean of the range is calculated, as well as the equalization coefficient by which the imaginary part should be scaled. The equalization coefficient is calculated by the following formula:

[0042] in, and Take the real and imaginary parts respectively.

[0043] In a specific implementation, the second signal is calculated by the following formula:

[0044] in, Indicates the second signal, represents the first signal. The signal after time domain equalization is as follows Figure 4 shown.

[0045] In a specific implementation, when the UWB radar system includes a transmitting antenna and two receiving antennas, the first phase difference from the target to the two receiving channels is calculated based on the motion signal, and the second phase difference of the two receiving channels is obtained after compensation, thereby obtaining the incident angle of the echo signal.

[0046] In a specific implementation, the first phase difference is calculated by the following formula:

[0047] in, and Represent the complex signals of the two channels respectively, and Represent the amplitudes of the two signals respectively. and They represent the phases of the two echo signals arriving at the receiver, and the two signals are conjugated and multiplied to obtain .

[0048] In a specific implementation, the second phase difference is calculated by the following formula:

[0049] in, To calculate the remainder, Indicates the fixed phase compensation value between receiving channels. It is used to compensate for the phase deviation between the two channels of the radar and the phase deviation caused by the inconsistency of the transmission signal time of the two channels.

[0050] In a specific implementation, the echo signal incident angle is calculated by the following formula:

[0051] in, represents the incident angle of the echo signal, represents the wavelength, Indicates the center frequency of the UWB radar pulse, Represents the speed of light.

[0052] In an ideal attitude, ignoring the height difference between the target and the UWB radar, this incident angle is the azimuth of the target relative to the radar. If the three-dimensional incident angle between the target and the UWB radar needs to be measured, a radar system with at least one transmitting antenna and three receiving antennas is required.

[0053] In a specific implementation, the real part or the imaginary part of the second signal is taken. ,but

[0054] Performing Hilbert transform gives constructing the third signal,

[0055] in, is the Cauchy principal value integral, which is used to deal with singular points in the integral. Indicates the third signal.

[0056] After the target distance and azimuth information is known, the position of the moving target in the polar coordinate system with the radar location as the origin can be directly obtained, such as Figure 5 As shown. On this basis, if there is a need for target tracking, Kalman filtering can be introduced to filter the target distance and azimuth information separately to eliminate measurement noise.

[0057] In summary, an embodiment of the present invention provides a UWB radar moving target detection and positioning method, the method comprising: performing FIR bandpass filtering on the original signal to obtain a first signal; performing FFT on the real and imaginary signals of the first signal at all range gates and calculating the peak-to-average ratio of the results; if the peak-to-average ratio is greater than a first threshold value, it is determined that a motion signal may have appeared; selecting a time domain signal with a preset window length on the range gate, and equalizing the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; calculating the direction through DOA; taking the real or imaginary part of the second signal, and performing After Hilbert transform, a third signal is constructed; a signal modulus value is calculated for the third signal, and when the signal modulus value is greater than a second threshold value, it is determined that a motion signal has appeared, and the first range gate where a signal appears is the target range gate; the position of the moving target is calculated according to the target range gate and the direction; the clutter, direct current and high-frequency noise components in the radar signal are effectively suppressed by performing bandpass filtering on the original CIR signal of the UWB radar system; the phase noise of the signal is effectively eliminated by time domain sliding equalization and Hilbert transform, thereby further improving the detection success rate and the reliability of radar ranging and direction finding; Furthermore, a real-time positioning method with good effect and low overhead is provided for UWB radar positioning; Furthermore, the method is cleverly designed, simple to implement, and has reliable ranging and direction finding detection accuracy, providing a feasible positioning method for low-cost UWB radars with high market value.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A UWB radar moving target detection and positioning method, characterized in that: The method comprises: Performing FIR bandpass filtering on the original signal to obtain a first signal; Performing FFT on the real and imaginary signals of the first signal at all range gates respectively and calculating the peak-to-average ratio of the results; If the peak-to-average ratio is greater than a first threshold value, it is determined that a motion signal may have occurred; Select a time domain signal with a preset window length on the range gate, and equalize the imaginary signal according to the peak-to-valley ratio of the real and imaginary signals in the window to obtain a second signal; Calculate direction through DOA; Taking the real part or the imaginary part of the second signal, performing Hilbert transform on the second signal, and constructing a third signal; Calculating a signal modulus value for the third signal, and when the signal modulus value is greater than a second threshold value, it is determined that a motion signal has appeared, and the first range gate where the signal appears is the target range gate; The position of the moving target is calculated according to the target range gate and the direction.

2. The UWB radar moving target detection and positioning method according to claim 1, characterized in that: If the peak-to-average ratio is greater than the first threshold value, the frequency point corresponding to the FFT peak is recorded. The frequency point is the Doppler frequency shift caused by the target movement. The movement speed of the target is obtained according to the Doppler frequency shift, which is specifically calculated by the following formula: in, represents the radial velocity of the target relative to the radar, Indicates the center frequency of the UWB radar pulse, represents the speed of light, Indicates the Doppler frequency deviation.

3. The UWB radar moving target detection and positioning method according to claim 1, characterized in that: The selecting of the time domain signal of the preset window length on the range gate includes selecting a sliding window for statistics, wherein the sliding step is less than 1 / 2 of the preset window length, and when sliding, recording the maximum and minimum values ​​of the real and imaginary parts of the first signal respectively, calculating the range and caching it.

4. The UWB radar moving target detection and positioning method as claimed in claim 3, characterized in that: After the window no longer contains the approximate sine wave caused by the Doppler effect, statistics are stopped and the mean of the range is calculated, as well as the equalization coefficient of the imaginary part scaling. The equalization coefficient is calculated by the following formula: in, and Take the real and imaginary parts respectively, Indicates the first signal.

5. The UWB radar moving target detection and positioning method according to claim 1, characterized in that: The second signal is calculated by the following formula: in, Indicates the second signal, Indicates the first signal.

6. The UWB radar moving target detection and positioning method according to claim 1, characterized in that: When the UWB radar system includes one transmitting antenna and two receiving antennas, the first phase difference from the target to the two receiving channels is calculated based on the motion signal, and the second phase difference of the two receiving channels is obtained after compensation, thereby obtaining the incident angle of the echo signal.

7. The UWB radar moving target detection and positioning method as claimed in claim 6, characterized in that: The first phase difference is calculated by the following formula: in, and Represent the complex signals of the two channels respectively, and Represent the amplitudes of the two signals respectively. and They represent the phases of the two echo signals arriving at the receiver, and the two signals are conjugated and multiplied to obtain .

8. The UWB radar moving target detection and positioning method as claimed in claim 7, characterized in that: The second phase difference is calculated by the following formula: in, To calculate the remainder, Indicates the fixed phase compensation value between receiving channels.

9. The UWB radar moving target detection and positioning method as claimed in claim 8, characterized in that: The incident angle of the echo signal is calculated by the following formula: in, represents the incident angle of the echo signal, represents the wavelength, Indicates the center frequency of the UWB radar pulse, Represents the speed of light.

10. The UWB radar moving target detection and positioning method according to claim 1, characterized in that: Take the real part or imaginary part of the second signal ,but Performing Hilbert transform gives constructing the third signal, in, is the Cauchy principal value integral, which is used to deal with singular points in the integral. Indicates the third signal.

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