Complementary phase coding sequence signal processing method based on distance sidelobe moving and Doppler compensation

Abstract

The invention discloses a complementary phase coding sequence signal processing method based on distance sidelobe shift and Doppler compensation, and relates to the technical field of radar signal processing, and the method comprises the steps: a radar transmitting signal employs a complementary coding sequence for phase modulation of a signal waveform; aD sampling, digital down-conversion and low-pass filtering are carried out on target echoes received by the radar, then the target echoes are rearranged into an echo signal matrix, and Doppler compensation is carried out on the echo signal matrix; and finally, pulse compression processing and moving target detection are performed on the compensated echo signal, target distance sidelobe moving is realized, and target distance-speed information is obtained. According to the complementary phase coding sequence signal processing method provided by the invention, the target distance sidelobe is effectively suppressed, the Doppler tolerance is improved, and an important technical support is provided for the complementary phase coding sequence signal in the field of low-altitude target detection.

Description

Technical Field

[0001] The present invention relates to the technical field of radar signal processing, and particularly to a complementary phase-coded sequence signal processing method based on range sidelobe migration and Doppler compensation. Background Art

[0002] Phase-Coded Radar is a radar system that achieves pulse compression through discrete phase modulation. Since phase coding uses a pseudo-random sequence, the phase-coded signal is also called a pseudo-random coded signal. Therefore, the phase-coded signal has excellent spread spectrum characteristics, good two-dimensional resolution, and good anti-interference and anti-interception capabilities.

[0003] However, as a pulse compression signal, the phase-coded signal also has some inherent disadvantages. First, the autocorrelation sidelobes of the phase-coded signal are relatively high, which may cause strong target sidelobes to mask weak targets, resulting in missed detection of weak targets and affecting the multi-target detection ability. Second, compared with the linear frequency modulation signal, the phase-coded signal is more sensitive to Doppler frequency shift, has a smaller Doppler tolerance, and is prone to signal mismatch, affecting the pulse compression performance and target recognition accuracy. These problems are particularly prominent in the detection of low-altitude targets because the Doppler frequency shift of low-altitude targets changes rapidly and unpredictably, and may be accompanied by strong clutter interference.

[0004] Regarding the sidelobe suppression problem of the phase-coded signal, the existing means currently include: methods based on weight window functions, adaptive filtering techniques, and methods based on iterative optimization. Sidelobe suppression based on the window function method reduces the sidelobes by adjusting the amplitude distribution of the signal. However, while reducing the sidelobes, these methods often widen the main lobe and reduce the range resolution of the radar. Especially in the detection of low-altitude targets, it may cause the target to be submerged in strong clutter and be difficult to effectively identify. The sidelobe suppression method based on adaptive filtering technology needs to dynamically adjust the filter coefficients to minimize sidelobe interference, but this method has a strong dependence on the clutter model and high computational complexity, and it is difficult to be realized in real time in the detection of low-altitude targets. The method based on iterative optimization optimizes the phase-coded sequence of the signal through an optimization algorithm to reduce the sidelobes, but this method requires a large number of iterative calculations and is prone to falling into local optimal solutions, and it is also difficult to meet the real-time requirements of low-altitude target detection.

[0005] To solve the problem of Doppler sensitivity of phase-coded signals, common Doppler compensation methods include: interpolation-based compensation methods, frequency-domain-based compensation methods, and waveform design-based Doppler compensation methods. The interpolation-based compensation method is prone to introducing interpolation errors due to the rapid change of the target Doppler frequency shift, resulting in insufficient compensation accuracy and high computational complexity; the frequency-domain-based compensation method has limited effectiveness in dealing with non-linear Doppler frequency shifts and also has a relatively high computational complexity, increasing the hardware burden and processing time of the system; the waveform design-based Doppler compensation method improves the Doppler tolerance of the signal by designing waveforms with high Doppler tolerance, but its design is complex and its adaptability is insufficient, making it difficult to cope with the variable Doppler frequency shift range of low-altitude targets, thus limiting its application in complex environments. Summary of the Invention

[0006] The object of the present invention is to provide a complementary phase-coded sequence signal processing method based on range sidelobe migration and Doppler compensation to solve the problems of high range sidelobes and Doppler sensitivity of phase-coded signals.

[0007] The technical solution for achieving the object of the present invention is: a complementary phase-coded sequence signal processing method based on range sidelobe migration and Doppler compensation, including:

[0008] The radar transmitted signal uses a signal waveform with phase modulation by a complementary coding sequence;

[0009] Receive and process the target echo and perform Doppler compensation;

[0010] Perform pulse compression processing and moving target detection on the compensated echo signal to achieve range sidelobe migration of the target and obtain the range-velocity information of the target.

[0011] Further, the radar transmitted signal is a signal waveform with phase modulation by a complementary coding sequence, its phase modulation function is a complementary phase-coded sequence, and it is modulated alternately by the positive code and the complementary code of the complementary sequence between pulses. The complex expression of the transmitted signal is:

[0012] s(t) = u(t)·exp(j2πf0t)

[0013] In the formula, f0 is the carrier frequency of the radar transmitted signal, j is the imaginary unit, exp(·) represents the exponential function with the natural constant e as the base, and u(t) is the complex envelope of the radar transmitted signal, and its expression is:

[0014]

[0015] where, c k ∈{+1, -1}, {c k} is a complementary phase coding sequence, u1(t) is the complex envelope of the radar transmitted signal sub-pulse, T is the sub-pulse width, k = 0, 1, 2, …, P - 1 is the sub-pulse ordinal number, P is the length of the complementary phase coding sequence {c k}, ∑ represents the summation operation, and u1(t) is expressed as:

[0016]

[0017] The aperiodic autocorrelation function of the complementary phase coding sequence is:

[0018]

[0019] where x represents the number of delay units, * represents the complex conjugate operation, and the aperiodic autocorrelation functions of the positive code and complementary code of the complementary phase coding sequence are R A (x) and R B (x), respectively, and satisfy the following conditions:

[0020]

[0021] Furthermore, receiving and processing the target echo and performing Doppler compensation specifically include the following steps:

[0022] Step 301: Perform AD sampling, digital down-conversion, and low-pass filtering on the target echo received by the radar, convert it into a zero-intermediate-frequency signal, and the sampling rate is f s ;

[0023] Step 302: The radar signal processing uses the coherent integration period as the processing time window, arranges the zero-intermediate-frequency signals in the order of the time of receiving the echo pulses into an echo signal matrix. Each echo signal matrix contains the echo signal data of one coherent integration period. Each row vector in the echo signal matrix represents the echo signal of one pulse repetition period. The odd row vectors are the positive code echo signals, and the even row vectors are the complementary code echo signals. The echo signal matrix is:

[0024]

[0025] where the number of rows N of the echo signal matrix is the number of pulse repetition periods included in each coherent integration period, N is an even number, the number of columns M of the echo signal matrix is the number of sampling points of the echo signal in each pulse repetition period, and s nm represents the element in the nth row and mth column of the matrix S NM ;

[0026] Step 303: Split the echo signal matrix according to the parity of the number of rows, and then expand and splice it by columns into a new matrix W LM ; For the matrix W LMPerform Fourier transform on each column vector, and multiply the transformed matrix by the Doppler compensation factor matrix ζ LM element by element; perform inverse Fourier transform on the multiplied matrix column by column, and finally, according to the splitting and splicing method of the echo signal matrix, reassemble the matrix after inverse Fourier transform into an N-row M-column matrix in reverse order, which is the echo signal matrix after Doppler compensation; the matrix W LM is:

[0027]

[0028] wherein, the new matrix W LM is L rows by 2M columns, L = N / 2, s (2l-1)m represents the element in the l-th row and m-th column of the matrix W LM , and s (2l)m represents the element in the l-th row and M+m-th column of the matrix W LM ; when n is odd, the element s NM in the matrix S nm is the same as the element s LM in the matrix W (2l-1)m , and when n is even, the element s NM in the matrix S nm is the same as the element s LM in the matrix W (2l)m ;

[0029] The Doppler compensation factor matrix is:

[0030]

[0031] wherein, f r is the pulse repetition frequency, and the echo signal matrix S' NM after Doppler compensation is:

[0032] S' NM = IFFT{(FFT(W LM ,1).*(ζ lm )),1}

[0033] In the formula, FFT([],1) represents performing Fourier transform on the matrix column by column, IFFT{[],1} represents performing inverse Fourier transform on the matrix column by column, and.* represents multiplying the corresponding elements of the two matrices.

[0034] Furthermore, performing pulse compression processing and moving target detection on the echo signal matrix after Doppler compensation specifically includes: performing pulse compression processing on the compensated target echo signal to initially obtain the distance information of the target; then performing moving target detection to realize the moving target range sidelobe migration and obtain the range-velocity information of the target. The range-velocity two-dimensional matrix output by the moving target detection is:

[0035] Z mtd = FFT{IFFT{FFT(S' NM , 2).* conj[FFT(S t , 2)], 2}, 1}

[0036] Wherein, FFT{[], 1} represents the Fourier transform of the matrix by column, FFT([], 2) represents the Fourier transform of the matrix by row, IFFT{[], 2} represents the inverse Fourier transform of the matrix by row, conj represents the conjugate of the matrix,.* represents the element-by-element multiplication of two matrices, and S t is the radar transmission signal matrix.

[0037] An electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the above method are implemented.

[0038] A computer-readable storage medium stores a computer program, and when the program is executed by a processor, the steps of the above method are implemented.

[0039] A computer program product includes a computer program, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0040] Compared with the prior art, the advantages of the present invention are as follows:

[0041] The present invention innovatively proposes a complementary phase coding sequence signal processing method based on range sidelobe migration and Doppler compensation. Starting from the signal coding design perspective, combining Doppler compensation technology, and then through corresponding signal processing methods, the range sidelobes are migrated and suppressed, while the Doppler tolerance of the phase coding signal is improved. The complementary phase coding sequence signal based on range sidelobe migration and Doppler compensation proposed by the present invention not only has good detection ability for low-altitude targets, but also has good anti-interference and anti-interception abilities due to its pseudo-randomness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flowchart of a complementary phase coding sequence signal processing method based on range sidelobe migration and Doppler compensation provided by the present invention.

[0043] Figure 2 is a schematic diagram of the transmitted pulse modulation waveform of a complementary phase coding radar based on range sidelobe migration and Doppler compensation provided by the present invention.

[0044] Figure 3 is a time-domain waveform diagram of a complementary phase coding sequence based on range sidelobe migration and Doppler compensation in an embodiment of the present invention.

[0045] Figure 4 The aperiodic autocorrelation function (AACF) of the positive code and the complementary code of the complementary phase-coded sequence based on range sidelobe migration and Doppler compensation in the embodiments of the present invention.

[0046] Figure 5 The real part and the imaginary part functions of the Doppler compensation factor of the signal processing method for the complementary phase-coded sequence based on range sidelobe migration and Doppler compensation in the embodiments of the present invention.

[0047] Figure 6 The comparison curve of the peak sidelobe ratio (PSLR) before and after Doppler compensation of the complementary phase-coded sequence signal in the embodiments of the present invention.

[0048] Figure 7 The signal processing result of the complementary phase-coded sequence based on range sidelobe migration and Doppler compensation in the embodiments of the present invention. Detailed implementation manners

[0049] For a clearer understanding of the technical features, objectives, and effects of the present invention, the detailed implementation manners of the present invention are now described with reference to the accompanying drawings.

[0050] The present invention proposes a signal processing method for a complementary phase-coded sequence based on range sidelobe migration and Doppler compensation. The signal processing method flow is as Figure 1 shown, and specifically includes:

[0051] Step 1: The radar transmits a signal waveform phase-modulated by a complementary coding sequence;

[0052] Step 2: Receive and process the target echo, and perform Doppler compensation;

[0053] Step 3: Perform pulse compression processing and moving target detection on the compensated echo signal to achieve range sidelobe migration of the target and obtain the range-velocity information of the target.

[0054] In this embodiment, Step 1 further includes:

[0055] The radar transmits a signal waveform phase-modulated by a complementary coding sequence. Its phase modulation function is a complementary phase-coded sequence, and the positive code and the complementary code of the complementary sequence are alternately modulated time-division between pulses, as Figure 2 shown. The complex expression of the transmitted signal is:

[0056] s(t) = u(t)·exp(j2πf0t)

[0057] Wherein, f0 is the carrier frequency of the radar transmitted signal, j is the imaginary unit, exp(·) represents the exponential function with the natural constant e as the base, and u(t) is the complex envelope of the radar transmitted signal, and the expression is:

[0058]

[0059] Among them, c k ∈{+1, -1}, {c k} is the complementary phase coding sequence. As Figure 3 shown, u1(t) is the complex envelope of the sub-pulse of the radar transmitted signal, T is the sub-pulse width, k = 0, 1, 2, …, P - 1 is the sub-pulse ordinal number, P is the length of the complementary phase coding sequence {c k}, ∑ represents the summation operation, and u1(t) is expressed as:

[0060]

[0061] The aperiodic autocorrelation function of the complementary phase coding sequence, as Figure 4 shown, the expression is:

[0062]

[0063] Among them, x represents the number of delay units, * represents the complex conjugate operation, and the aperiodic autocorrelation functions of the positive code and the complementary code of the complementary phase coding sequence are R A (x) and R B (x) respectively, and satisfy the following conditions:

[0064]

[0065] In this embodiment, step two further includes:

[0066] Performing reception processing on the target echo and performing Doppler compensation, specifically including the following steps:

[0067] Step 301: Perform AD sampling, digital down-conversion, and low-pass filtering on the target echo received by the radar, and convert it into a zero-intermediate frequency signal, and the sampling rate is f s ;

[0068] Step 302: The radar signal processing uses the coherent accumulation period as the processing time window, arranges the zero-intermediate frequency signals in the order of the time of receiving the echo pulses, and forms an echo signal matrix. Each echo signal matrix contains the echo signal data of a coherent accumulation period. Each row vector in the echo signal matrix represents the echo signal of a pulse repetition period. The odd row vectors are the positive code echo signals, and the even row vectors are the complementary code echo signals. The echo signal matrix is:

[0069]

[0070] Among them, the number of rows N of the echo signal matrix is the number of pulse repetition periods included in each coherent accumulation period, N is an even number, and the number of columns M of the echo signal matrix is the number of sampling points of the echo signal in each pulse repetition period. s nm represents the matrix S NM the element in the n-th row and m-th column of

[0071] Step 303: Split the echo signal matrix according to the parity of the number of rows, then expand and splice it by columns into a new matrix W LM ; For each column vector of the matrix W LM perform a Fourier transform, multiply the elements of the transformed matrix with the corresponding elements of the Doppler compensation factor matrix ζ LM ; Perform an inverse Fourier transform on the multiplied matrix by columns, and finally, according to the splitting and splicing method of the echo signal matrix, recombine the matrix after the inverse Fourier transform reversely into an N-row and M-column matrix, which is the echo signal matrix after Doppler compensation; the matrix W LM is:

[0072]

[0073] Among them, the new matrix W LM is L rows and 2M columns, L = N / 2, s (2l-1)m represents the element in the l-th row and m-th column of the matrix W LM , s (2l)m represents the element in the l-th row and M + m-th column of the matrix W LM ; When n is odd, the element s NM in the matrix S nm is the same as the element s LM in the matrix W (2l-1)m ; When n is even, the element s NM in the matrix S nm is the same as the element s LM in the matrix W (2l)m ;

[0074] The described Doppler compensation factor matrix, as Figure 5 shown, the expression is:

[0075]

[0076] Among them, f r is the pulse repetition frequency, and the echo signal matrix S' NM after Doppler compensation is:

[0077] S' NM = IFFT{(FFT(W LM , 1).*(ζ lm )), 1}

[0078] In the formula, FFT([],1) represents performing a Fourier transform on the matrix column by column, IFFT{[],1} represents performing an inverse Fourier transform on the matrix column by column, and.* represents multiplying the corresponding elements of two matrices.

[0079] In this embodiment, step three further includes:

[0080] Performing pulse compression processing and moving target detection on the echo signal matrix after Doppler compensation, specifically including: performing pulse compression processing on the compensated target echo signal to initially obtain the distance information of the target, and the target peak sidelobe ratio curve is as Figure 6 shown; then performing moving target detection to achieve the moving of the target range sidelobes, as Figure 7 shown, and obtaining the range-velocity information of the target. The range-velocity two-dimensional matrix output by the moving target detection is:

[0081] Z mtd = FFT{IFFT{FFT(S' NM ,2).* conj[FFT(S t ,2)],2},1}

[0082] In the formula, FFT{[],1} represents performing a Fourier transform on the matrix column by column, FFT([],2) represents performing a Fourier transform on the matrix row by row, IFFT{[],2} represents performing an inverse Fourier transform on the matrix row by row, conj represents taking the conjugate of the matrix,.* represents multiplying the corresponding elements of two matrices, and S t is the radar transmit signal matrix.

[0083] In the example of the present invention, by simulating the time-domain waveform diagram of a complementary phase-coded sequence based on range sidelobe migration and Doppler compensation, the non-periodic autocorrelation function (AACF), the Doppler compensation factor, the comparison curves of the peak sidelobe ratio (PSLR) before and after Doppler compensation, and the signal processing results of the complementary phase-coded sequence based on range sidelobe migration and Doppler compensation, the advantages of the present invention are illustrated. The signal processing parameter settings are shown in Table 1, and the target simulation parameters are shown in Table 2.

[0084] In the specific implementation process, the software platform is: the Matlab simulation experiment platform.

[0085] Table 1

[0086]

[0087]

[0088] Table 2

[0089]

[0090] Figure 3 and Figure 4 give the time-domain waveform diagram of a complementary phase-coded sequence based on range sidelobe migration and Doppler compensation, as well as the aperiodic autocorrelation functions (AACFs) of the positive code and the complementary code respectively. Figure 5 is the real and imaginary part functions of the Doppler compensation factor. Figure 6 is the comparison curve of the peak sidelobe ratio (PSLR) of the complementary phase-coded sequence signal before and after Doppler compensation. It can be seen that after Doppler compensation, the Doppler tolerance of the complementary phase-coded sequence signal has been greatly improved and the Doppler sensitivity has been reduced.

[0091] From Figure 7 it can be seen that after processing the complementary phase-coded sequence signal based on range sidelobe migration and Doppler compensation, the main peaks of two targets with different speeds are clearly visible. The range sidelobes of the targets are migrated to the edge of the two-dimensional matrix, which does not affect the detection of low, small, and slow targets. At the same time, the sidelobes caused by Doppler are suppressed, and weak targets are no longer covered by the sidelobes of strong targets.

[0092] The above embodiments illustrate and describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements. These changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A signal processing method for complementary phase-coded sequence based on range sidelobe migration and Doppler compensation, characterized in that Including: A signal waveform in which the radar transmitted signal is phase - modulated using a complementary coding sequence; Receiving and processing the target echo, and performing Doppler compensation; Performing pulse compression processing and moving target detection on the compensated echo signal to achieve moving of the target range sidelobe and obtain the range - velocity information of the target.

2. The method for processing complementary phase coding sequence signals based on distance sidelobe migration and Doppler compensation according to claim 1, wherein The phase - modulation function of the radar transmitted signal is a complementary phase - coding sequence, and is modulated alternately by the positive code and the complementary code of the complementary sequence at different times between pulses. The complex expression of the transmitted signal is: s(t) = u(t)·exp(j2πf0t) In the formula, f0 is the carrier frequency of the radar transmitted signal, j is the imaginary unit, exp(·) represents the exponential function with the natural constant e as the base, and u(t) is the complex envelope of the radar transmitted signal, and its expression is: where c k ∈ {+1, -1}, {c k} is a complementary phase coding sequence, u1(t) is the complex envelope of the radar transmitted signal sub-pulse, T is the sub-pulse width, k = 0, 1, 2, ..., P - 1 is the sub-pulse ordinal number, P is the length of the complementary phase coding sequence {c k}, ∑ represents the summation operation, and u1(t) is expressed as: The aperiodic autocorrelation function of the complementary phase - coding sequence is: where x represents the number of time delay units, * represents the complex conjugate operation, and the aperiodic autocorrelation functions of the positive code and complementary code of the complementary phase coding sequence are R A (x) and R B (x), respectively, and satisfy the following conditions:

3. The method for processing complementary phase-coded sequence signals based on distance sidelobe migration and Doppler compensation according to claim 2, wherein, Receiving and processing the target echo and performing Doppler compensation specifically includes the following steps: Step 301: Perform AD sampling, digital down-conversion, and low-pass filtering on the target echo received by the radar, convert it into a zero-intermediate frequency signal, and the sampling rate is f s ; Step 302: The radar signal processing takes the coherent integration period as the processing time window, arranges the zero - intermediate - frequency signals in the order of the time of receiving the echo pulses into an echo signal matrix. Each echo signal matrix contains the echo signal data of one coherent integration period. Each row vector in the echo signal matrix represents the echo signal of one pulse repetition period. The odd - numbered row vectors are the positive - code echo signals, and the even - numbered row vectors are the complementary - code echo signals. The echo signal matrix is: Among them, the number of rows N of the echo signal matrix is the number of pulse repetition periods included in each coherent accumulation period, N is an even number, the number of columns M of the echo signal matrix is the number of sampling points of the echo signal in each pulse repetition period, and s nm represents the matrix S NM represents the element in the n-th row and m-th column of Step 303: Split the echo signal matrix according to the parity of the number of rows, then expand and splice it by columns to form a new matrix W LM ; For the matrix W LM , perform Fourier transform on each column vector. Multiply the corresponding elements of the transformed matrix by the Doppler compensation factor matrix ζ LM ; Perform inverse Fourier transform on the multiplied matrix by columns. Finally, according to the splitting and splicing method of the echo signal matrix, reversely recombine the matrix after inverse Fourier transform into an N-row and M-column matrix, which is the echo signal matrix after Doppler compensation; The matrix W LM is: Among them, the new matrix W LM is L rows by 2M columns, where L = N / 2, and s (2l-1)m represents the element in the l-th row and m-th column of matrix W LM , and s (2l)m represents the element in the l-th row and (M + m)-th column of matrix W LM ; when n is odd, the element s NM in matrix S nm is the same as the element s LM in matrix W (2l-1)m , and when n is even, the element s NM in matrix S nm is the same as the element s LM in matrix W (2l)m ; The Doppler compensation factor matrix is: where f r is the pulse repetition frequency.

4. The method for processing complementary phase-coded sequence signals based on distance sidelobe migration and Doppler compensation according to claim 3, wherein Performing pulse compression processing and moving target detection on the Doppler - compensated echo signal matrix includes: performing pulse compression processing on the compensated target echo signal to initially obtain the range information of the target; then performing moving target detection to achieve moving of the target range sidelobe and obtain the range - velocity information of the target.

5. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in any one of claims 1 - 4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method described in any one of claims 1 - 4.

7. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method described in any one of claims 1 - 4.

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