A multi-channel digital synthesis method for 5G external radiation source radar based on amplitude and phase correction

Abstract

A multi-channel digital synthesis method for 5G external radiation source radar based on amplitude and phase correction, the specific steps are as follows: S1, generate a local reference signal according to the collected 5G direct wave signal information; S2, perform cross-correlation operation on the 5G target echo signal collected by each channel and the local signal, and find the peak point of the cross-correlation result of each channel through maximum likelihood judgment; S3, select the first channel as the reference channel, and calculate the phase difference and amplitude difference of the peak point between each channel and the reference channel in multiple synchronization signal block periods; S4, obtain the preliminary calibration coefficients of the amplitude and phase of each channel at the time of signal acquisition by averaging the phase difference and amplitude difference; S5, optimize the calibration coefficient within the adjustment interval according to the minimum mean square error of the signal before and after correction; S6, compensate for the amplitude phase difference of each channel; S7, digitally synthesize multi-channel data. This method uses the data after channel calibration for digital synthesis, which improves the intensity of the target echo signal and is conducive to further detection of the target.

Description

Technical Field

[0001] The present invention relates to the technical field of exo-radiation source radar, and in particular to a multi-channel digital synthesis method of a 5G exo-radiation source radar based on amplitude and phase correction. Background Art

[0002] Exo-radiation radar is a new type of radar. It does not radiate electromagnetic energy outward, but uses signals in space (such as TV stations, GPS satellites, 5G signals, etc.) as illumination sources and relies on passive reception of reflected signals from targets to achieve target detection. As 5G (fifth-generation mobile communication technology) becomes the mainstream communication signal, exo-radiation target positioning based on 5G base stations has become an important research direction.

[0003] In the external radiation source radar, the receiving antenna is used to receive the echo signal, and the single-channel acquisition is adopted. The resolution is low, and the target cannot be accurately detected and located. At the same time, there is a lot of noise. In order to improve the sensitivity and accuracy of target detection, by combining information from different channels, false alarms can be reduced and the target and detection probability can be increased. In the multi-channel multi-antenna external radiation source radar system, there is a phase difference when the multi-chip local oscillator is locked, and there are errors in the RF, analog-to-digital conversion and antenna processing. Therefore, there are amplitude and phase errors between multi-channel multi-antennas, which reduces the strength of the collected target echo signal. It is necessary to use a new method to correct the amplitude and phase of the 5G signal collected by multiple channels and synthesize it to improve the detection probability.

[0004] Compared with existing technologies:

[0005] Technical comparison with patent CN116718989A "A method for radar clutter cancellation and target detection of large-scale antenna external radiation source";

[0006] Patent CN116718989A uses the capture and code loop tracking of navigation satellite signals, while we use 5G communication signals as external radiation sources and use signal cross-correlation operations to extract the synchronization signal block part of the 5G signal from a complex noise environment. We first obtain prior information based on the collected 5G direct wave signal, including the transmission mode of the synchronization signal block (SSB), the number of beams, the number of occupied resource blocks (RBs), the subcarrier spacing, the length of the OFDM symbol, the cyclic prefix length of the OFDM symbol, etc.

[0007] Patent CN102572970A adopts a method of constructing a dual-channel compensation function and combining it with the Keystone transform to avoid the complex matrix operation of obtaining the compensation factor, and correct the distance movement and clutter phase difference at one time. However, this study uses a method of twice correcting the amplitude and phase of multi-channel 5G echo signal acquisition. The 5G signals collected by each channel are subjected to sliding cross-correlation operation with the locally generated reference signal, namely the synchronization signal block. The phase difference and amplitude difference at the peak points between each channel and the reference channel within multiple synchronization signal block periods are used to obtain the preliminary calibration coefficients of the amplitude and phase of each channel at the signal acquisition time by averaging the phase difference and amplitude difference. Then, the preliminary calibration coefficients of the amplitude and phase are adjusted within the set range respectively, and the optimized channel calibration coefficient is obtained by controlling the mean square error of the signal before and after correction of each receiving channel to be minimized.

[0008] Technical comparison with patent CN105093191A "External radiation source radar direct wave recovery method";

[0009] 1. Patent CN105093191A uses one equalizer to process the diversity signal of each diversity channel to obtain multi-channel equalizer output signals, and sums the multi-channel equalizer output signals to obtain direct wave signals. This study uses a preliminary calibration of the amplitude and phase of the 5G echo signal collected by the channel, and then uses interval adjustment to calibrate the optimized calibration coefficient with the minimum mean square error, and digitally synthesizes the data after the calibration of each channel.

[0010] 2. Patent CN105093191A uses direct wave signals to calculate the error term, and calculates the mean square error of the error term to determine whether the mean square error is less than a preset threshold. However, since 5G signals are discontinuously transmitted, this study sets a signal threshold when calculating the signal error. If the threshold is exceeded, the error calculation is involved to reduce the impact of noise. The minimum mean square error of the error signal is then calculated to find the optimal calibration coefficient. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction to solve the problems raised in the above background technology.

[0012] To achieve the above object, the present invention provides a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction, comprising the following method steps:

[0013] S1. Generate a local reference signal, specifically a synchronization signal block SSB, based on the collected prior information of the 5G direct wave signal;

[0014] S2. After the signals of each channel are roughly synchronized, the 5G signals collected by each channel are subjected to sliding cross-correlation operation with the locally generated reference signal, i.e., the synchronization signal block, and the peak point of the cross-correlation result between each channel signal and the local reference signal is found through maximum likelihood judgment;

[0015] S3, select the first channel as the reference channel, and calculate the phase difference and amplitude difference between the peak points of each channel and the reference channel in multiple synchronization signal block periods;

[0016] S4, obtaining the preliminary calibration coefficients of the amplitude and phase of each channel at the time of signal acquisition by averaging the phase difference and the amplitude difference;

[0017] S5, adjusting the amplitude and phase preliminary calibration coefficients within the set range respectively, and obtaining the optimized channel calibration coefficient by controlling the mean square error of the signals before and after correction of each receiving channel to be minimum;

[0018] S6. Compensating the amplitude phase difference of each channel according to the optimized channel calibration coefficient to achieve receiving channel correction;

[0019] S7, digitally synthesizing the calibrated data of each channel.

[0020] Further, S2 includes generating a local reference signal x(n) based on the prior information of the collected 5G direct wave signal and performing coarse signal synchronization, and then synchronizing the 5G signal y collected by each channel. i (n) is cross-correlated with the local signal x(n), and its expression is:

[0021]

[0022] Among them, R i (m) represents the result obtained by cross-correlating the 5G signal collected by the i-th channel with the local signal, m represents the selected sliding window width, and N is the number of sampling points of the 5G signal collected by the channel;

[0023] Then, the peak point of the cross-correlation results of each channel is found through maximum likelihood judgment, and its expression is:

[0024] (P i ,x i )=argmax(R i (m))

[0025] Among them, the peak point of the cross-correlation result of the i-th channel is P i , the horizontal coordinate value of the peak point of the cross-correlation result of the i-th channel is x i .

[0026] Further, the S3 includes intercepting equal-segment signals from each channel, selecting the first channel as a reference channel, finding the peak value after cross-correlation between the intercepted signal from each channel and the local signal, and finding the phase difference and amplitude difference between the peak points of each channel and the reference channel, and the expression is:

[0027]

[0028] Where K is the total number of peaks after the intercepted signal and the local signal are cross-correlated, θ1(k) is the phase of the peak point of the first receiving channel, i.e., the reference channel, and θ i (k) is the phase of the peak point of the i-th receiving channel, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, P1(k) is the amplitude of the peak point of the reference channel, P i (k) is the amplitude of the peak point of the i-th channel, ΔP 1i (k) is the amplitude difference ratio between the peak points of the i-th channel and the reference channel;

[0029] The average amplitude difference is obtained by taking the average value of the amplitude difference and phase difference between the peak points of each channel and the reference channel. The average phase difference Its expression is:

[0030]

[0031] Among them, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, ΔP 1i (k) is the ratio of the amplitude difference between the peak points of the i-th channel and the reference channel, and K is the number of peaks after the intercepted signal is cross-correlated with the local signal.

[0032] Further, the S4 includes obtaining a preliminary calibration coefficient c of the i-th receiving channel by calculating the average value of the phase difference and the amplitude difference. i , whose expression is:

[0033]

[0034] in, is the average amplitude difference ratio, is the average phase difference.

[0035] Further, S5 includes adjusting the amplitude and phase preliminary calibration coefficients within the set range respectively, and obtaining the optimized channel calibration coefficient by controlling the mean square error of the signal before and after correction to be minimum. The optimized calibration coefficient C i The expression is:

[0036]

[0037] Among them, P adj_i is the amplitude adjusted for the i-th receiving channel, θ adj_i The phase adjusted for the i-th receiving channel must be within the range of the set step size and range;

[0038] The correction signal error is obtained by subtracting the calibrated signal from the reference signal. Since 5G signals are discontinuously transmitted, a signal threshold needs to be set when calculating the signal error. If the signal strength exceeds the threshold, the error is included in the error calculation. Otherwise, the error at the sampling point is 0, thereby reducing the influence of noise. The correction signal error E of the i-th channel i (n) The expression is:

[0039]

[0040] Among them, y1(n) is the reference channel receiving signal, C i is the calibration coefficient of the ith channel after adjustment, y th is the signal threshold, then the expression of the signal mean square error is:

[0041]

[0042] Among them, E i (n) is the error between the calibrated signal of the i-th channel and the reference channel signal, and N is the number of sampling points of each receiving channel signal;

[0043] In the adjustment range, the mean square error of the channel signal before and after correction with different correction coefficients is calculated respectively. When the mean square error reaches the minimum, the corresponding channel calibration coefficient is the optimized channel calibration coefficient.

[0044] The present invention relates to the technical field of external radiation source radar, and is specifically a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction, and the specific steps are as follows: S1, generate a local reference signal according to the collected 5G direct wave signal information; S2, perform cross-correlation operation on the 5G target echo signal collected by each channel and the local signal, and find the peak point of the cross-correlation result of each channel by maximum likelihood judgment; S3, select the first channel as the reference channel, and calculate the phase difference and amplitude difference of the peak point of each channel and the reference channel in multiple synchronization signal block cycles; S4, obtain the initial calibration coefficient of the amplitude and phase of each channel at the time of signal acquisition by averaging the phase difference and amplitude difference; S5, optimize the calibration coefficient within the adjustment interval according to the minimum mean square error of the signal before and after correction; S6, compensate for the amplitude phase difference of each channel; S7, digitally synthesize multi-channel data. The method obtains the initial calibration coefficient of the amplitude and phase of the 5G signal collected by each channel through cross-correlation operation and optimizes the calibration coefficient according to the mean square error, and uses the data after channel calibration for digital synthesis, thereby improving the intensity of the target echo signal and facilitating further detection of the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments:

[0046] Figure 1 It is a schematic diagram of external radiation source radar positioning of the present invention;

[0047] Figure 2 This is a schematic diagram of the 5G downlink signal structure;

[0048] Figure 3 It is a multi-channel digital synthesis flow chart of 5G external radiation source radar. DETAILED DESCRIPTION

[0049] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0050] The present invention provides a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction through improvement. The technical solution of the present invention is aimed at the 5G signal external radiation source radar, and its structure is as follows: Figure 1 As shown, the receiver of the external radiation source radar generally has multiple receiving antennas.

[0051] In this embodiment, the echo signal received by the receiving antenna is a 5G signal, and its structure is as follows: Figure 2 As shown. The 5G downlink signal uses cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) technology. The principle is to convert the input data into serial / parallel, modulate the data onto multiple orthogonal subcarriers through inverse Fourier transform (IFFT), and insert a cyclic prefix (CP). Five different types of subcarrier spacing (SCS) Δf=2 are set in the 5G downlink signal. μ 15kHz (μ=0,1,2,3,4), each OFDM spectrum has a length of T1=1 / Δf, each 5G subframe consists of only a fixed number of time slots, and the number of subframe time slots is 2 μ The 5G signal physical layer introduces the concept of synchronization signal block (SSB), which includes the primary synchronization signal (PSS) and the secondary synchronization signal (SSS). The primary synchronization signal (PSS) can be used to determine the cell index and the time synchronization at the OFDM level, time slot, and half-frame, while the secondary synchronization signal (SSS) can be used to determine the CP type and frame-level time synchronization.

[0052] The implementation process flow chart is as follows: Figure 3 As shown, the specific steps are as follows:

[0053] S1. Use signal cross-correlation operation to extract the synchronization signal block part in the 5G signal from the complex noise environment. First, generate the local reference signal x(n) based on the prior information of the collected 5G direct wave signal, including the transmission mode of the synchronization signal block (SSB), the number of beams, the number of occupied resource blocks (RB), the subcarrier spacing, the length of the OFDM symbol, the cyclic prefix length of the OFDM symbol, etc.

[0054] S2. Since the extraction of the amplitude difference and phase difference of the receiving channel utilizes the correlation of the signal, it is necessary to first generate a local reference signal x(n), i.e., a synchronization signal block, based on the prior information of the collected 5G direct wave signal, and convert the 5G signal y collected by each channel into a local reference signal x(n). i (n) is cross-correlated with the local signal x(n), and its expression is:

[0055]

[0056] Among them, R i (m) represents the result of cross-correlation between the 5G signal collected by the i-th channel and the local signal, m represents the selected sliding window width, and N is the number of sampling points of the 5G signal collected by the channel. Then, all the peak points of the cross-correlation results of each channel are found through maximum likelihood judgment, and the expression is:

[0057] (P i ,x i )=argmax(R i (m))

[0058] Among them, the peak point of the cross-correlation result of the i-th channel is P i , the horizontal coordinate value of the peak point of the cross-correlation result of the i-th channel is x i .

[0059] S3. Each channel intercepts equal-segment signals, selects the first channel as the reference channel, calculates the peak number of each channel intercepted signal after cross-correlation with the local signal, and calculates the phase difference and amplitude difference of the peak point between each channel and the reference channel. The expression is:

[0060]

[0061] Where K is the total number of peaks after the intercepted signal and the local signal are cross-correlated, θ1(k) is the phase of the peak point of the first receiving channel, i.e., the reference channel, and θ i (k) is the phase of the peak point of the i-th receiving channel, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, P1(k) is the amplitude of the peak point of the reference channel, P i(k) is the amplitude of the peak point of the i-th channel, ΔP 1i (k) is the amplitude difference ratio between the peak points of the i-th channel and the reference channel;

[0062] The average amplitude difference is obtained by taking the average value of the amplitude difference and phase difference between the peak points of each channel and the reference channel. The average phase difference Its expression is:

[0063]

[0064] Among them, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, ΔP 1i (k) is the ratio of the amplitude difference between the peak points of the i-th channel and the reference channel, and K is the number of peaks after the intercepted signal is cross-correlated with the local signal.

[0065] S4. The preliminary calibration coefficient of the receiving channel is obtained by calculating the average value of the phase difference and the amplitude difference. The expression is:

[0066]

[0067] in, is the average amplitude difference ratio, is the average phase difference;

[0068] S5. Adjust the amplitude and phase preliminary calibration coefficients within the set range respectively. By controlling the mean square error of the signal before and after correction to the minimum, the optimized channel calibration coefficient is obtained. The optimized calibration coefficient C i The expression is:

[0069]

[0070] Among them, P adj_i is the amplitude adjusted for the i-th receiving channel, θ adj_i The phase adjusted for the i-th receiving channel must be within the set step size and range to reduce the amount of calculation.

[0071] The calibration error is obtained by subtracting the calibrated signal from the reference signal. Since 5G signals are discontinuously transmitted, a signal threshold needs to be set when calculating the signal error. If the signal strength exceeds the threshold, the error is included in the error calculation. Otherwise, the error at the sampling point is 0, thereby reducing the impact of noise. Its expression is:

[0072]

[0073] Among them, y1(n) is the reference channel receiving signal, C i is the calibration coefficient of the ith channel after adjustment, y this the signal threshold. Then the expression of the signal mean square error is:

[0074]

[0075] In the adjustment range, the mean square error of the channel signal before and after correction with different correction coefficients is calculated respectively. When the mean square error reaches the minimum, the corresponding channel calibration coefficient is the optimized channel calibration coefficient.

[0076] S6. Use the optimized calibration coefficient to compensate each channel to achieve receiving channel calibration and obtain the corrected data, which is expressed as:

[0077] Y i (n) = y i (n) C i

[0078] Among them, the data collected by each channel is y i (n), the data collected and corrected by other channels is Y i (n);

[0079] S7, digitally synthesize the corrected results of the i-channel collected data, and the mathematical expression is:

[0080]

[0081] Among them, y1(n) is the signal collected by the reference channel, Y i (n) is the signal after amplitude and phase correction of other receiving channels, M is the total number of receiving channels, and r(n) is the result of digital synthesis.

[0082] Through the above steps, the 5G signals with inconsistent amplitude and phase collected by multi-channel are corrected, and the target echo signal strength based on multi-channel digital synthesis of 5G signals is improved, which is beneficial to further target detection.

[0083] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction, characterized by: The method comprises the following steps: S1. Generate a local reference signal, specifically a synchronization signal block SSB, based on the collected prior information of the 5G direct wave signal; S2. After the signals of each channel are roughly synchronized, the 5G signals collected by each channel are subjected to sliding cross-correlation operation with the local reference signal, i.e., the synchronization signal block, and the peak point of the cross-correlation result between the signals of each channel and the local reference signal is found through maximum likelihood judgment; S3, select the first channel as the reference channel, and calculate the phase difference and amplitude difference between the peak points of each channel and the reference channel in multiple synchronization signal block periods; S4, obtaining the preliminary calibration coefficients of the amplitude and phase of each channel at the time of signal acquisition by averaging the phase difference and the amplitude difference; S5, adjusting the amplitude and phase preliminary calibration coefficients within the set range respectively, and obtaining the optimized channel calibration coefficient by controlling the mean square error of the signals before and after correction of each receiving channel to be minimum; S6. Compensating the amplitude phase difference of each channel according to the optimized channel calibration coefficient to achieve receiving channel correction; S7, digitally synthesizing the calibrated data of each channel.

2. According to the 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction according to claim 1, it is characterized by: S2 includes generating a local reference signal x(n) based on the prior information of the collected 5G direct wave signal and performing coarse signal synchronization, and then collecting the 5G direct wave signal y from each channel. i (n) performs cross-correlation operation with the local reference signal x(n), and its expression is: Among them, R i (m) represents the result obtained by cross-correlating the 5G signal collected by the i-th channel with the local reference signal, m represents the selected sliding window width, and N is the number of sampling points of the 5G signal collected by the channel; Then, the peak point of the cross-correlation results of each channel is found through maximum likelihood judgment, and its expression is: (P i ,x i )=argmax(R i (m)) Among them, the peak point of the cross-correlation result of the i-th channel is P i , the horizontal coordinate value of the peak point of the cross-correlation result of the i-th channel is x i .

3. According to claim 2, a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction is characterized in that: S3 includes intercepting equal-segment signals from each channel, selecting the first channel as a reference channel, finding the peak number of the intercepted signal from each channel after cross-correlation with the local reference signal, and finding the phase difference and amplitude difference between the peak points of each channel and the reference channel, and the expression is: Where K is the total number of peaks after the intercepted signal is cross-correlated with the local reference signal, θ1(k) is the phase of the peak point of the first receiving channel, i.e., the reference channel, and θ i (k) is the phase of the peak point of the i-th receiving channel, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, P1(k) is the amplitude of the peak point of the reference channel, P i (k) is the amplitude of the peak point of the i-th channel, ΔP 1i (k) is the amplitude difference ratio between the peak points of the i-th channel and the reference channel; The average amplitude difference is obtained by taking the average value of the amplitude difference and phase difference between the peak points of each channel and the reference channel. The average phase difference Its expression is: Among them, Δθ 1i (k) is the phase difference between the peak point of the i-th channel and the reference channel, ΔP 1i (k) is the ratio of the amplitude difference between the peak points of the i-th channel and the reference channel, and K is the total number of peaks after the intercepted signal is cross-correlated with the local reference signal.

4. According to the 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction according to claim 3, it is characterized in that: S4 includes obtaining a preliminary calibration coefficient c of the i-th receiving channel by calculating the average value of the phase difference and the amplitude difference. i , whose expression is: in, is the average amplitude difference ratio, is the average phase difference.

5. According to claim 4, a 5G external radiation source radar multi-channel digital synthesis method based on amplitude and phase correction is characterized in that: S5 includes adjusting the amplitude and phase preliminary calibration coefficients within the set range respectively, and obtaining the optimized channel calibration coefficient by controlling the mean square error of the signal before and after correction to be minimum. The optimized calibration coefficient C i The expression is: Among them, P adj_i is the amplitude adjusted for the i-th receiving channel, θ adj_i The phase adjusted for the i-th receiving channel must be within the range of the set step size and range; The correction signal error is obtained by subtracting the calibrated signal from the reference signal. Since 5G signals are discontinuously transmitted, a signal threshold needs to be set when calculating the signal error. If the signal strength exceeds the threshold, the error is included in the error calculation. Otherwise, the error at the sampling point is 0, thereby reducing the influence of noise. The correction signal error E of the i-th channel i (n) The expression is: Among them, y1(n) is the reference channel receiving signal, C i is the calibration coefficient of the ith channel after adjustment, y th is the signal threshold, then the expression of the signal mean square error is: Among them, E i (n) is the error between the calibrated signal of the i-th channel and the reference channel signal, and N is the number of sampling points of the 5G signal collected by the channel; In the adjustment range, the mean square error of the channel signal before and after correction with different correction coefficients is calculated respectively. When the mean square error reaches the minimum, the corresponding channel calibration coefficient is the optimized channel calibration coefficient.

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