Distributed single-bit radar Doppler coherent detection method

Abstract

The invention discloses a distributed single-bit radar Doppler coherent detection method, which relates to the technical field of radar signal processing, and comprises the following steps: a plurality of substations respectively carry out single-bit quantization processing on received signals to obtain single-bit digital signals, and a central station directly collects received multi-bit signals; the Doppler spectrum of the target is obtained; respectively obtaining coherent and non-coherent Doppler spectrums according to whether phase information is reserved or not; calculating each velocity vector point in the plane, and superposing Doppler spectrum values of a plurality of base stations through coherent accumulation; and through the maximum value of the frequency spectrum, the maximum statistical magnitude is extracted, and existence test of the target is carried out to realize Doppler detection. According to the distributed single-bit radar Doppler coherent detection method, through reasonable signal processing and an optimized spectrum superposition strategy, the target detection capability of the system is improved, and the Doppler detection precision is improved under the condition of low signal-to-noise ratio.

Description

Technical Field

[0001] The invention relates to the technical field of radar signal processing, and in particular to a distributed single-bit radar Doppler coherent detection method. Background Art

[0002] In a distributed radar system, higher target detection accuracy and stronger anti-interference ability can be achieved by working together with multiple dispersed radar nodes. Among them, the target detection accuracy depends largely on the accurate estimation of the target Doppler frequency. In traditional methods, the high-precision sampling and signal processing of the radar system consumes a lot of computing and storage resources. Especially in complex environments, the system detection performance is seriously affected by factors such as noise, interference, and multipath effects. Therefore, the existing technology urgently needs an efficient and low-cost Doppler frequency estimation method in complex environments to improve the target detection capability of distributed single-bit radar systems.

[0003] Doppler detection based on single-bit quantization technology in distributed radar systems is an emerging technology in the field of radar signal processing. This method greatly reduces the complexity of data storage and transmission by quantizing the echo signal into single-bit data. At the same time, it combines core technologies such as coherent accumulation and multi-node collaborative processing to achieve a good balance between signal processing efficiency and detection accuracy. This technology can achieve high-precision estimation of the target Doppler frequency through the synergy of distributed nodes under low signal-to-noise ratio conditions, and effectively cope with the influence of external environments such as noise and interference.

[0004] Existing distributed single-bit radar systems face the following major problems in target Doppler coherent detection: 1. Noise and interference: The radar received signal is affected by noise and other interference sources, which may interfere with the signal processing step. Especially in a low signal-to-noise ratio environment, the target signal is easily masked by the background noise, which will reduce the precision and accuracy of the target Doppler detection.

[0005] 2. Quantization error and performance loss: Single-bit quantization only retains the sign information of the signal, which will introduce quantization error and cause serious loss of signal amplitude information. This will not only affect the accuracy of matched filtering and frequency compensation in signal processing, but also directly affect the performance of Doppler detection of the target.

[0006] 3. Complexity of multi-node data fusion: In distributed radar systems, there are significant differences in the quality and amount of information of target signals received by different nodes, and the existing data fusion methods cannot make full use of this differential information, resulting in the failure to achieve the optimal effect of multi-node collaboration.

[0007] The present invention improves the Doppler detection method and applies it to the distributed single-bit radar system by processing the detection problem at a special spatial point, thereby improving the accuracy of target Doppler detection under low signal-to-noise ratio conditions, thereby significantly improving the estimation performance. It is a very promising and effective method to reduce its complexity and power consumption. Summary of the invention

[0008] The purpose of the present invention is to provide a distributed single-bit radar Doppler coherent detection method, which solves the problems of signal amplitude information loss and insufficient Doppler resolution caused by single-bit quantization in traditional methods through matched filtering, hybrid sampling method and coherent detection, and can significantly improve the target Doppler detection performance in low signal-to-noise ratio and complex environment.

[0009] To achieve the above object, the present invention provides a distributed single-bit radar Doppler coherent detection method, comprising the following steps: Step S1: adopting a hybrid sampling method of single-bit sampling at the substation and multi-bit sampling at the central station, the substation quantizes the received analog baseband signal through a single-bit analog-to-digital converter ADC to obtain a single-bit digital signal to transmit data, while the central station directly retains the multi-bit signal received by the base station without transmitting data; Step S2, using the obtained single-bit signal and the conjugate of the transmission signal to perform matched filtering, and then performing FFT processing on the Doppler dimension of the matched filtered signal to obtain a Doppler spectrum; Step S3, obtaining a coherent Doppler spectrum and a non-coherent Doppler spectrum respectively according to whether the phase information is retained, the coherent Doppler spectrum directly performs spectrum superposition, and the non-coherent Doppler spectrum extracts the maximum value of the Doppler spectrum of each base station; Step S4: In processing special spatial points, the target velocity vector plane is traversed, discrete weights corresponding to the Doppler frequency are pre-arranged, and then each velocity vector point in the plane is calculated, and the Doppler spectrum values ​​of each base station are superimposed by coherent accumulation; Step S5: By calculating the maximum value of the velocity plane, the maximum statistics under the H0 hypothesis and the H1 hypothesis are obtained respectively. T The statistic is used to evaluate the target's existence and realize Doppler detection.

[0010] Preferably, the step S1 specifically includes: Consider a distributed radar system, which includes three radar base stations for transmission and reception and one moving target. After sampling and discretization, the radar transmission signal is expressed as , taking the linear frequency modulation LFM signal as an example, The transmission signal of a base station is expressed as: (1) in, , is the index of a single pulse sampling point, is the total number of sampling points for a single pulse, is the frequency modulation slope, is the signal bandwidth, is the pulse duration, is the sampling frequency, is an imaginary unit; Assume that the transmitters and receivers of the three radar base stations are at the same location. The distance between the base station and the target is set to , then The propagation delay of the signal received by each base station is: (2) in, is the speed of light; Assume The target radial velocity of each base station is , No. The Doppler frequency of a base station is expressed as: (3) in, is the wavelength of the transmitted signal; Under the influence of Doppler frequency and time delay, The target echo signal received by each base station is expressed as: (4) in, , is the index of the Doppler dimension, For the The target reflection coefficient of each base station is is the pulse repetition time, is the total number of sampling points for a pulse repetition time, is the number of pulses; For the outstation, the received echo signal is quantized by a single-bit analog-to-digital converter with a zero threshold to obtain a single-bit digital signal. The single-bit digital signal of a substation is expressed as: (5) in, , is the symbolic function, and Represent the real and imaginary parts of the signal respectively; For the central station, the received echo signal retains the multi-bit form. Assuming that the first base station in the distributed single-bit radar system is the central station, the received signal of the central station is expressed as: (6) in, is the target reflection coefficient of the first base station, is the transmission signal of the first base station, is the propagation delay of the signal received by the first base station, is the Doppler frequency of the first base station.

[0011] Preferably, the step S2 specifically includes: After matched filtering using the conjugate of the obtained single-multi-bit signal and the transmitted signal, the The matched filter output of each base station is: (7) in, , is the complex conjugate symbol, is the convolution symbol, is the index of the sampling point, is the total number of sampling points for a pulse repetition time, is the index of the Doppler dimension, is the number of pulses, the matched filter output is a size of Matrix of Perform fast Fourier transform (FFT) processing on the Doppler dimension and obtain The Doppler spectrum of a base station is expressed as: (8) in, , It is a fast Fourier transform processing operation, which means extracting spectrum information in the Doppler frequency dimension.

[0012] Preferably, the step S3 specifically includes: The coherent method performs coherent superposition of the Doppler spectra of each base station and uses the phase information of the received signal of each base station to accumulate signal energy, thereby improving the energy concentration of the target signal. The coherent Doppler spectrum is directly expressed as the Doppler spectrum after matched filtering. ; The non-coherent method does not retain the phase information of the signal, and obtains the first The non-coherent Doppler spectrum of a base station is: (9) The results of coherent and non-coherent Doppler spectra are finally indexed by frequency in the Doppler dimension. expressed in the form of .

[0013] Preferably, the step S4 specifically includes the following steps: Firstly, the search range and resolution of the velocity vector plane are defined, and a discrete weight index matrix corresponding to the Doppler frequency is established during the traversal process, so as to quickly superimpose the Doppler spectrum values ​​of multiple base stations and finally complete the Doppler detection. Search range for velocity vector planes and is the theoretical maximum value of the Doppler frequency passing through the system Calculated, Defined as: (10) The search range of the target in the horizontal and vertical speed directions is determined by formula (9) and is expressed as ; The horizontal velocity on the velocity vector plane and vertical axis speed It is divided by equally spaced discrete points, and the number of points is determined by the length of the FFT in the Doppler dimension. The division formula is as follows: (11) in, , , is the velocity vector in the plane discrete points on the horizontal axis, represents the velocity vector in the plane The velocity vector plane is divided into a discrete point on the vertical axis by the above formula. A two-dimensional discrete search grid, where each grid point represents a velocity vector; For each velocity vector point, the theoretical Doppler frequency value of the velocity vector point on each base station is calculated according to the position of the base station and the moving direction of the target. The calculation formula is: (12) in, , and It is with The coefficient related to the geometric position of each base station is determined by the relative position and velocity direction of the base station and the target, and is expressed as: (13) The target location is , No. The location of the base station is , after obtaining the Doppler frequency of each base station Finally, by matching the calculated frequency value with the discrete points of the Doppler spectrum axis, the nearest discrete point index is found as: (14) in, The value of the independent variable that minimizes the function value is is the discrete frequency value of the Doppler spectrum axis, expressed as: (15) in, , for each velocity vector point, the corresponding discrete frequency index will be stored in the index matrix In the corresponding position of By traversing each point on the velocity vector plane, the Doppler spectrum value of each base station at the velocity vector point is quickly extracted using the pre-stored index matrix. , the frequency spectrum value of the velocity vector plane is obtained as: (16) in, For the Doppler spectrum value of each base station on the velocity vector plane; By integrating the spectrum values ​​of all base stations through coherent accumulation, the spectrum after superposition of three base stations is obtained: (17) in, .

[0014] Preferably, the step S5 specifically includes: Based on the superimposed spectrum of three base stations , extract the maximum value of the spectrum amplitude to obtain the maximum statistics, the expression of the maximum statistics is: (18) Identify whether the target exists based on the maximum statistic, where Assume no target. For a targeted hypothesis, the standard testing problem is described as a binary hypothesis test: (19) in, is complex Gaussian white noise, is the first Single-bit digital signal of each substation, The echo signal received by the substation; For statistics , through a threshold To determine whether the detection problem belongs to still : (20) Among them, the threshold According to the probability of detection and false alarm probability Make adjustments to meet system performance requirements; The performance of target detection is and Further evaluation, including: (twenty one) Finally, through the statistics and performance indicators and Through the analysis, effective evaluation of target existence can be achieved, thereby completing the Doppler coherent detection of distributed single-bit radar.

[0015] Therefore, the present invention adopts the above-mentioned distributed single-bit radar Doppler coherent detection method, and improves the system's detection capability of the target through reasonable signal processing and optimized spectrum superposition strategy, and improves the Doppler detection accuracy under low signal-to-noise ratio conditions. At the same time, since the single-bit analog-to-digital converter only retains the signal symbol information, it is a very promising detection method that reduces complexity and power consumption.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of an embodiment of a distributed single-bit radar Doppler coherent detection method of the present invention; Figure 2 The velocity plane map of the present invention, wherein (a) is a velocity plane map processed by coherence, and (b) is a velocity plane map processed by non-coherence; Figure 3 Graphs showing the relationship between parameters of the coherent processing and the non-coherent processing of the present invention, wherein (a) is a graph showing the relationship between the false alarm rate and the threshold, and (b) is a graph showing the relationship between the detection probability and the threshold; Figure 4 It is the ROC curve diagram of the coherent processing and the non-coherent processing of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example See also Figure 1-4 The present invention provides a distributed single-bit radar Doppler coherent detection method, comprising the following steps: Step S1: adopting the hybrid sampling method of single-bit at the substation and multi-bit at the central station, the substation quantizes the received analog baseband signal through a single-bit analog-to-digital converter ADC to obtain a single-bit digital signal to transmit data, while the central station directly retains the multi-bit signal received by the base station without transmitting data. Specifically including: Consider a distributed radar system, which includes three radar base stations for transmission and reception and one moving target. In this system, it is assumed that the transmitted signal is known, and a mixed sampling method of single-bit at the substation and multi-bit at the central station is adopted. The substation performs single-bit quantization processing on the received signal to obtain a single-bit signal, while the central station directly retains the received multi-bit signal. Since the distributed radar base stations are located in different positions, their distances and angles from the target are different, so the received echo signals will show differences in time delay, Doppler frequency and reflection coefficient. These differences need to be fully considered in the signal processing process to achieve accurate estimation of the target Doppler parameters and optimization of system performance.

[0021] After sampling and discretization, the radar transmission signal is expressed as , taking the linear frequency modulation LFM signal as an example, The transmission signal of a base station is expressed as: (1) in, , is the index of a single pulse sampling point, is the total number of sampling points for a single pulse, is the frequency modulation slope, is the signal bandwidth, is the pulse duration, is the sampling frequency, is an imaginary unit; Assume that the transmitters and receivers of the three radar base stations are at the same location. The distance between the base station and the target is set to , then The propagation delay of the signal received by each base station is: (2) in, is the speed of light; Assume The target radial velocity of each base station is , No. The Doppler frequency of a base station is expressed as: (3) in, is the wavelength of the transmitted signal; Under the influence of Doppler frequency and time delay, The target echo signal received by each base station is expressed as: (4) in, , is the index of the Doppler dimension, For the The target reflection coefficient of each base station is is the pulse repetition time, is the total number of sampling points for a pulse repetition time, is the number of pulses; For the outstation, the received echo signal is quantized by a single-bit analog-to-digital converter with a zero threshold to obtain a single-bit digital signal. The single-bit digital signal of a substation is expressed as: (5) in, , is the symbolic function, and Represent the real and imaginary parts of the signal respectively; For the central station, the received echo signal retains the multi-bit form. Assuming that the first base station in the distributed single-bit radar system is the central station, the received signal of the central station is expressed as: (6) in, is the target reflection coefficient of the first base station, is the transmission signal of the first base station, is the propagation delay of the signal received by the first base station, is the Doppler frequency of the first base station.

[0022] This hybrid sampling method of single-bit at substations and multi-bit at central stations not only significantly reduces the data transmission bandwidth requirements of the entire distributed radar system, but also ensures the system's high-precision signal processing capabilities, thereby taking into account both system efficiency and performance, and can effectively improve the accuracy of target detection and parameter estimation.

[0023] Step S2: Use the obtained single-bit signal and the conjugate of the transmitted signal to perform matched filtering, and then perform FFT processing on the Doppler dimension of the matched filtered signal to obtain the Doppler spectrum. Specifically including: Matched filtering is a widely used method in distributed radar to enhance the target signal while suppressing the influence of noise. After matching filtering using the conjugate of the obtained single-bit or multi-bit signal and the transmitted signal, the The matched filter output of each base station is: (7) in, , is the complex conjugate symbol, is the convolution symbol, is the index of the sampling point, is the total number of sampling points for a pulse repetition time, is the index of the Doppler dimension, is the number of pulses, the matched filter output is a size of A matrix of (corresponding to the total number of samples in the range dimension and the number of pulses in the Doppler dimension) that extracts the portion of the received signal that matches the transmitted signal.

[0024] Perform fast Fourier transform (FFT) processing on the Doppler dimension and obtain The Doppler spectrum of a base station is expressed as: (8) in, , It is a fast Fourier transform processing operation, which means extracting spectrum information in the Doppler frequency dimension.

[0025] Step S3, based on the Doppler spectrum after matched filtering, obtain the coherent Doppler spectrum and the non-coherent Doppler spectrum respectively according to whether the phase information is retained. The coherent Doppler spectrum directly superimposes the spectrum, and the non-coherent coherent Doppler spectrum extracts the maximum value of the Doppler spectrum of each base station. Specifically including: The coherent method accumulates the signal energy by coherently superimposing the Doppler spectra of each base station and using the phase information of the received signal of each base station, thereby improving the energy concentration of the target signal. Therefore, the coherent Doppler spectrum is directly expressed as the Doppler spectrum after matched filtering .

[0026] In contrast, the non-coherent method does not retain the phase information of the signal, and obtains the first The non-coherent Doppler spectrum of a base station is: (9) The results of coherent and non-coherent Doppler spectra are finally indexed by frequency in the Doppler dimension. The subsequent signal processing step extracts the Doppler frequency information of the target by extracting the frequency index, so as to further analyze the detection performance.

[0027] Step S4, in the processing of special spatial points, that is, at the position point where the target corresponding to the delay index may exist, in order to more efficiently realize the target velocity vector estimation, the method of traversing the target velocity vector plane is adopted, and the discrete weights corresponding to the Doppler frequency are pre-arranged, and then each velocity vector point in the plane is calculated, and the Doppler spectrum values ​​of each base station are superimposed through coherent accumulation to achieve fast processing and calculation optimization. Specifically, the core operation is to pre-calculate the discrete weights corresponding to the Doppler frequency at different base stations and different speed directions, and use these discrete weights to sum each point in the velocity vector plane, and then integrate the Doppler spectrum values ​​of multiple base stations through coherent accumulation, so as to realize the target Doppler coherent detection of the distributed single-bit radar. Specifically including: First, the velocity vector plane is divided and traversed according to the predefined velocity search range and resolution. The goal is to detect the velocity information of the target by traversing all possible velocity vector points in the velocity vector plane and combining the discrete Doppler spectrum values ​​for weighted superposition and coherent accumulation. To achieve this goal, it is first necessary to define the search range and resolution of the velocity vector plane, and establish a discrete weight index matrix corresponding to the Doppler frequency during the traversal process, and then quickly superimpose the Doppler spectrum values ​​of multiple base stations to finally complete the Doppler detection; Search range for velocity vector planes and is the theoretical maximum value of the Doppler frequency passing through the system Calculated, Defined as: (10) The search range of the target in the horizontal and vertical speed directions is determined by formula (9) and is expressed as ; The horizontal velocity on the velocity vector plane and vertical axis speed It is divided by equally spaced discrete points, and the number of points is determined by the length of the FFT in the Doppler dimension. The division formula is as follows: (11) in, , , is the velocity vector in the plane discrete points on the horizontal axis, represents the velocity vector in the plane The velocity vector plane is divided into a discrete point on the vertical axis by the above formula. A two-dimensional discrete search grid, where each grid point represents a velocity vector; For each velocity vector point, the theoretical Doppler frequency value of the velocity vector point on each base station is calculated according to the position of the base station and the moving direction of the target. The calculation formula is: (12) in, , and It is with The coefficient related to the geometric position of each base station is determined by the relative position and velocity direction of the base station and the target, and is expressed as: (13) The target location is , No. The location of the base station is , after obtaining the Doppler frequency of each base station Finally, by matching the calculated frequency value with the discrete points of the Doppler spectrum axis, the nearest discrete point index is found as: (14) in, The value of the independent variable that minimizes the function value is is the discrete frequency value of the Doppler spectrum axis, expressed as: (15) in, , for each velocity vector point, the corresponding discrete frequency index will be stored in the index matrix In the corresponding position of By traversing each point on the velocity vector plane, the Doppler spectrum value of each base station at the velocity vector point is quickly extracted using the pre-stored index matrix. , the frequency spectrum value of the velocity vector plane is obtained as: (16) in, For the Doppler spectrum value of each base station on the velocity vector plane; By integrating the spectrum values ​​of all base stations through coherent accumulation, the spectrum after superposition of three base stations is obtained: (17) in, The above method optimizes the calculation process by using discrete index matrix, which greatly reduces the calculation complexity while ensuring accuracy.

[0028] Step S5: By calculating the maximum value of the velocity plane, the maximum statistics under the H0 hypothesis and the H1 hypothesis are obtained respectively. T And use this statistic to evaluate the existence of the target and realize Doppler detection. Specifically include: Based on the superimposed spectrum of three base stations , extract the maximum value of the spectrum amplitude to obtain the maximum statistics, the expression of the maximum statistics is: (18) Identify whether the target exists based on the maximum statistic, where Assume no target. For a targeted hypothesis, the standard testing problem is described as a binary hypothesis test: (19) in, is complex Gaussian white noise, is the first Single-bit digital signal of each substation, The echo signal received by the substation; For statistics , through a threshold To determine whether the detection problem belongs to still : (20) Among them, the threshold According to the probability of detection and false alarm probability Make adjustments to meet system performance requirements; The performance of target detection is and Further evaluation, including: (twenty one) Finally, through the statistics and performance indicators and Through the analysis, effective evaluation of target existence can be achieved, thereby completing the Doppler coherent detection of distributed single-bit radar.

[0029] Combined with Figure 1 , the specific implementation steps of the present invention are described as follows: Step S1, first, the present invention considers a distributed radar system, which includes three radar base stations for transmitting and receiving and one moving target. In this system, it is assumed that the transmitted signal is known, the first base station is a central station receiving multi-bit signals, and the second and third base stations are substations receiving single-bit signals. The parameters are set as follows: the number of transmitted pulses The complex Gaussian white noise obeys a complex Gaussian distribution with a mean of 0 and a variance of 1. The position coordinates of the three base stations are set to [0,0], [10000,0], and [0,5000], respectively. The position coordinates of the target are set to [5000,5000], the velocity vector of the target is set to [-5,-10], and the signal-to-noise ratio is -35dB.

[0030] The analog baseband signal received by each substation is quantized by a single-bit analog-to-digital converter to obtain a single-bit digital signal.

[0031] In this simulation experiment, the radar signal is set to the LFM signal: ; Get the first The receiving signal of each substation is: ; The single-bit digital signal obtained by quantization is: .

[0032] Step S2: Use the obtained single-multi-bit signal and the conjugate inversion of the transmitted signal to perform matched filtering to enhance the target echo characteristics in the signal while suppressing noise interference. Perform FFT processing along the Doppler dimension according to the matched filtering result of the signal model to extract the Doppler spectrum of the target. .

[0033] Step S3: obtaining a coherent Doppler spectrum and a non-coherent Doppler spectrum respectively according to whether the phase information is retained.

[0034] Step S4: traverse the target velocity vector plane In this way, each velocity vector point is calculated point by point, and the phase information of the received signal of each base station is used through coherent accumulation to enhance the energy of the target signal and suppress noise, thus realizing the superposition of the Doppler spectrum of each base station. Finally, in the entire velocity vector plane, the position with the maximum superimposed spectrum value is found, which corresponds to the true velocity vector of the target, thus realizing Doppler coherent detection, such as Figure 2 shown. Figure 2 The velocity plane spectra of coherent processing and non-coherent processing are drawn in the figure. The black △ is the true value of the target velocity [-5, -10], and the red × is the estimated value. Coherent Doppler detection combines phase information to make the signal energy highly concentrated at the velocity vector point corresponding to the target, and forms a clearer peak in the velocity plane, such as Figure 2 (a) The peak position marked in red. Figure 2 (b) Since the non-coherent Doppler detection does not utilize the phase information of the signal, its signal energy is more dispersed on the velocity plane, the target peak is not as significant as the coherent method, and the background noise appears to be stronger. This dispersed energy distribution will reduce the detection performance of the target, especially under low signal-to-noise ratio conditions. Therefore, the coherent method is significantly superior to the non-coherent method in terms of target positioning accuracy and noise suppression ability, showing higher detection accuracy and robustness.

[0035] Step S5: Based on the established signal model, the detection probability of single-bit Doppler detection is finally generated after 1*105 Monte Carlo simulation tests under the condition of -35dB signal-to-noise ratio. and false alarm rate As the threshold changes, such as Figure 3 As shown. Figure 3 (a) It can be seen that coherent Doppler detection shows obvious performance advantages over incoherent Doppler detection. In the comparison of false alarm rate with threshold change, coherent detection (red curve) can reduce the false alarm probability faster than incoherent detection (blue curve). When the threshold value increases, the false alarm probability of coherent detection decreases more steeply, indicating that it has a stronger ability to suppress noise and interference within the threshold range. Figure 3 (b) It can be seen that coherent detection can maintain a high detection probability when the threshold is low, showing a strong ability to capture the target signal. Even as the threshold increases, the performance of coherent detection decreases slowly, and it always maintains good target detection performance. Figure 4 In the figure, the ROC curve shows the relationship between false alarm rate and detection probability. The ROC curve of coherent detection (red) is significantly better than that of non-coherent detection (blue), as shown by the curve being closer to the upper left corner. This shows that coherent detection can maintain a high detection probability under a low false alarm probability, reflecting its excellent performance in target detection tasks. In general, the performance of coherent Doppler detection is better. Figure 3and Figure 4 Both reflect the strong robustness and anti-interference ability of coherent detection to target signals.

[0036] Therefore, the present invention adopts the above-mentioned distributed single-bit radar Doppler coherent detection method, and improves the system's detection capability of the target through reasonable signal processing and optimized spectrum superposition strategy, and improves the Doppler detection accuracy under low signal-to-noise ratio conditions.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A distributed single-bit radar Doppler coherent detection method, characterized in that: The following steps are involved: Step S1: adopting a hybrid sampling method of single-bit sampling at the substation and multi-bit sampling at the central station, the substation quantizes the received analog baseband signal through a single-bit analog-to-digital converter ADC to obtain a single-bit digital signal to transmit data, while the central station directly retains the multi-bit signal received by the base station without transmitting data; Step S2, using the obtained single-bit signal and the conjugate of the transmission signal to perform matched filtering, and then performing FFT processing on the Doppler dimension of the matched filtered signal to obtain a Doppler spectrum; Step S3, obtaining a coherent Doppler spectrum and a non-coherent Doppler spectrum respectively according to whether the phase information is retained, the coherent Doppler spectrum directly performs spectrum superposition, and the non-coherent Doppler spectrum extracts the maximum value of the Doppler spectrum of each base station; Step S4: In processing special spatial points, the target velocity vector plane is traversed, discrete weights corresponding to the Doppler frequency are pre-arranged, and then each velocity vector point in the plane is calculated, and the Doppler spectrum values ​​of each base station are superimposed by coherent accumulation; Step S5: By calculating the maximum value of the velocity plane, the maximum statistics under the H0 hypothesis and the H1 hypothesis are obtained respectively. T The statistic is used to evaluate the target's existence and realize Doppler detection.

2. The distributed single-bit radar Doppler coherent detection method according to claim 1, characterized in that: The step S1 specifically includes: Consider a distributed radar system, which includes three radar base stations for transmission and reception and one moving target. After sampling and discretization, the radar transmission signal is expressed as , taking the linear frequency modulation LFM signal as an example, The transmission signal of a base station is expressed as: （1） in, , is the index of a single pulse sampling point, is the total number of sampling points for a single pulse, is the frequency modulation slope, is the signal bandwidth, is the pulse duration, is the sampling frequency, is an imaginary unit; Assume that the transmitters and receivers of the three radar base stations are at the same location. The distance between the base station and the target is set to , then The propagation delay of the signal received by each base station is: （2） in, is the speed of light; Assume The target radial velocity of each base station is , No. The Doppler frequency of a base station is expressed as: （3） in, is the wavelength of the transmitted signal; Under the influence of Doppler frequency and time delay, The target echo signal received by each base station is expressed as: （4） in, , is the index of the Doppler dimension, For the The target reflection coefficient of each base station is is the pulse repetition time, is the total number of sampling points for a pulse repetition time, is the number of pulses; For the outstation, the received echo signal is quantized by a single-bit analog-to-digital converter with a zero threshold to obtain a single-bit digital signal. The single-bit digital signal of a substation is expressed as: （5） in, , is the symbolic function, and Represent the real and imaginary parts of the signal respectively; For the central station, the received echo signal retains the multi-bit form. Assuming that the first base station in the distributed single-bit radar system is the central station, the received signal of the central station is expressed as: （6） in, is the target reflection coefficient of the first base station, is the transmission signal of the first base station, is the propagation delay of the signal received by the first base station, is the Doppler frequency of the first base station.

3. The distributed single-bit radar Doppler coherent detection method according to claim 1, characterized in that: The step S2 specifically includes: After matched filtering using the conjugate of the obtained single-multi-bit signal and the transmitted signal, the The matched filter output of each base station is: （7） in, , is the complex conjugate symbol, is the convolution symbol, is the index of the sampling point, is the total number of sampling points for a pulse repetition time, is the index of the Doppler dimension, is the number of pulses, the matched filter output is a size of Matrix of Perform fast Fourier transform (FFT) processing in the Doppler dimension to obtain The Doppler spectrum of a base station is expressed as: （8） in, , It is a fast Fourier transform processing operation, which means extracting spectrum information in the Doppler frequency dimension.

4. The distributed single-bit radar Doppler coherent detection method according to claim 13, characterized in that: The step S3 specifically includes: The coherent method performs coherent superposition of the Doppler spectra of each base station and uses the phase information of the received signal of each base station to accumulate signal energy, thereby improving the energy concentration of the target signal. The coherent Doppler spectrum is directly expressed as the Doppler spectrum after matched filtering. ; The non-coherent method does not retain the phase information of the signal, and obtains the first The non-coherent Doppler spectrum of a base station is: （9） The results of coherent and non-coherent Doppler spectra are finally indexed by frequency in the Doppler dimension. expressed in the form of .

5. The distributed single-bit radar Doppler coherent detection method according to claim 1, characterized in that: The step S4 specifically comprises the following steps: Firstly, the search range and resolution of the velocity vector plane are defined, and a discrete weight index matrix corresponding to the Doppler frequency is established during the traversal process, so as to quickly superimpose the Doppler spectrum values ​​of multiple base stations and finally complete the Doppler detection. Search range for velocity vector planes and is the theoretical maximum value of the Doppler frequency passing through the system Calculated, Defined as: （10） The search range of the target in the horizontal and vertical speed directions is determined by formula (9) and is expressed as ; The horizontal velocity on the velocity vector plane and vertical axis speed It is divided by equally spaced discrete points, and the number of points is determined by the length of the FFT in the Doppler dimension. The division formula is as follows: （11） in, , , is the velocity vector in the plane discrete points on the horizontal axis, represents the velocity vector in the plane The velocity vector plane is divided into a discrete point on the vertical axis by the above formula. A two-dimensional discrete search grid, where each grid point represents a velocity vector; For each velocity vector point, the theoretical Doppler frequency value of the velocity vector point on each base station is calculated according to the position of the base station and the moving direction of the target. The calculation formula is: （12） in, , and It is with The coefficient related to the geometric position of each base station is determined by the relative position and velocity direction of the base station and the target, and is expressed as: （13） The target location is , No. The location of the base station is , after obtaining the Doppler frequency of each base station Finally, by matching the calculated frequency value with the discrete points of the Doppler spectrum axis, the nearest discrete point index is found as: （14） in, The value of the independent variable that minimizes the function value is is the discrete frequency value of the Doppler spectrum axis, expressed as: （15） in, , for each velocity vector point, the corresponding discrete frequency index will be stored in the index matrix In the corresponding position of By traversing each point on the velocity vector plane, the Doppler spectrum value of each base station at the velocity vector point is quickly extracted using the pre-stored index matrix. , the frequency spectrum value of the velocity vector plane is obtained as: （16） in, For the Doppler spectrum value of each base station on the velocity vector plane; By integrating the spectrum values ​​of all base stations through coherent accumulation, the spectrum after superposition of three base stations is obtained: （17） in, .

6. The distributed single-bit radar Doppler coherent detection method according to claim 1, characterized in that: The step S5 specifically includes: Based on the superimposed spectrum of three base stations , extract the maximum value of the spectrum amplitude to obtain the maximum statistics, the expression of the maximum statistics is: （18） Identify whether the target exists based on the maximum statistic, where Assume no target. For a targeted hypothesis, the standard testing problem is described as a binary hypothesis test: （19） in, is complex Gaussian white noise, is the first Single-bit digital signal of each substation, The echo signal received by the substation; For statistics , through a threshold To determine whether the detection problem belongs to still : （20） Among them, the threshold According to the probability of detection and false alarm probability Make adjustments to meet system performance requirements; The performance of target detection is and Further assessment, including: （21） Finally, through statistics and performance indicators and Through the analysis, effective evaluation of target existence can be achieved, thereby completing the Doppler coherent detection of distributed single-bit radar.

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