Doppler coherent detection method for distributed single-bit radar

Abstract

The present invention discloses a distributed single-bit radar Doppler coherent detection method, which relates to the field of radar signal processing technology, and includes the following steps: multiple substations perform single-bit quantization processing on received signals respectively to obtain single-bit digital signals, and a central station directly collects the received multi-bit signals; obtains the Doppler spectrum of the target; obtains coherent and non-coherent Doppler spectra respectively according to whether phase information is retained; calculates each velocity vector point in the plane, and superimposes the Doppler spectrum values ​​of multiple base stations through coherent accumulation; extracts the maximum statistic through the maximum value of the spectrum, and performs a target existence test to achieve Doppler detection. 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.

Description

Technical Field

[0001] The present 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 distributed radar systems, the collaborative operation of multiple dispersed radar nodes enables higher target detection accuracy and stronger anti-interference capabilities. Target detection accuracy relies heavily on accurately estimating the target's Doppler frequency. Traditionally, high-precision sampling and signal processing in radar systems consume significant computing and storage resources. This is particularly true in complex environments, where system detection performance is severely impacted by factors such as noise, interference, and multipath. Therefore, there is an urgent need for an efficient and low-cost Doppler frequency estimation method in complex environments to improve the target detection capabilities of distributed single-bit radar systems.

[0003] Doppler detection in distributed radar systems based on single-bit quantization is an emerging technology in radar signal processing. By quantizing echo signals into single-bit data, this method significantly reduces the complexity of data storage and transmission. By combining core technologies such as coherent accumulation and multi-node collaborative processing, it achieves a good balance between signal processing efficiency and detection accuracy. This technology enables high-precision estimation of the target's Doppler frequency under low signal-to-noise ratio conditions through the coordinated action of distributed nodes, effectively addressing external environmental influences such as noise and interference.

[0004] Existing distributed single-bit radar systems face the following major problems in target Doppler coherent detection:

[0005] 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.

[0006] 2. Quantization error and performance loss: Single-bit quantization retains only the signal sign information, which introduces quantization error and leads to significant loss of signal amplitude information. This not only affects the accuracy of matched filtering and frequency compensation in signal processing, but also directly affects the performance of target Doppler detection.

[0007] 3. Complexity of multi-node data fusion: In distributed radar systems, the quality and amount of target signals received by different nodes vary significantly, and existing data fusion methods cannot fully utilize this differential information, resulting in suboptimal multi-node collaboration.

[0008] By addressing the detection problem at special spatial points, the present invention improves the Doppler detection method and applies it to distributed single-bit radar systems, thereby improving the accuracy of target Doppler detection under low signal-to-noise ratio conditions, thereby significantly improving estimation performance. This is a promising and effective method to reduce its complexity and power consumption. Summary of the Invention

[0009] The purpose of the present invention is to provide a distributed single-bit radar Doppler coherent detection method. Through matched filtering, hybrid sampling method and coherent detection, the method solves the problems of signal amplitude information loss and insufficient Doppler resolution caused by single-bit quantization in traditional methods, and can significantly improve the target Doppler detection performance in low signal-to-noise ratio and complex environments.

[0010] To achieve the above object, the present invention provides a distributed single-bit radar Doppler coherent detection method, comprising the following steps:

[0011] Step S1: A hybrid sampling method of single-bit sampling at the substation and multi-bit sampling at the central station is adopted. The substation quantizes the received analog baseband signal through a single-bit analog-to-digital converter (ADC) to obtain a single-bit digital signal for data transmission, while the central station directly retains the multi-bit signal received by the base station without transmitting data.

[0012] Step S2: performing matched filtering using the obtained single-bit signal and the conjugate of the transmitted signal, and then performing FFT processing on the Doppler dimension of the matched filtered signal to obtain a Doppler spectrum;

[0013] Step S3: obtaining a coherent Doppler spectrum and a non-coherent Doppler spectrum respectively according to whether the phase information is retained, directly superimposing the coherent Doppler spectrum, and extracting the maximum value of the Doppler spectrum of each base station for the non-coherent Doppler spectrum;

[0014] Step S4: In processing the possible target location points corresponding to the delay index, 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 through coherent accumulation;

[0015] Step S5: Calculate the maximum value of the velocity plane to obtain the maximum statistics under the H0 hypothesis and the H1 hypothesis respectively. T The statistic is used to evaluate the target's existence and realize Doppler detection.

[0016] Preferably, the step S1 specifically includes:

[0017] 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 transmitted signal of a base station is expressed as:

[0018] (1)

[0019] 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;

[0020] 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:

[0021] (2)

[0022] in, is the speed of light;

[0023] Assume that The target radial velocity of each base station is , No. The Doppler frequency of a base station is expressed as:

[0024] (3)

[0025] in, is the wavelength of the transmitted signal;

[0026] Under the influence of Doppler frequency and time delay, the The target echo signal received by each base station is expressed as:

[0027] (4)

[0028] in, , is the index of the Doppler dimension, For the The target reflection coefficient of each base station, is the pulse repetition time, is the total number of sampling points for a pulse repetition time, is the number of pulses;

[0029] 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:

[0030] (5)

[0031] in, , is a symbolic function, and represent the real and imaginary parts of the signal respectively;

[0032] 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:

[0033] (6)

[0034] 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.

[0035] Preferably, the step S2 specifically includes:

[0036] After matched filtering using the conjugate of the obtained single-bit and multi-bit signals and the transmitted signal, the The matched filter output of each base station is:

[0037] (7)

[0038] 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, matched filter output is a size of Matrix of

[0039] Perform fast Fourier transform (FFT) processing on the Doppler dimension to obtain the The Doppler spectrum of a base station is expressed as:

[0040] (8)

[0041] in, , It is a fast Fourier transform processing operation, which means extracting spectrum information in the Doppler frequency dimension.

[0042] Preferably, the step S3 specifically includes:

[0043] 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. ;

[0044] 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:

[0045] (9)

[0046] The results of coherent and non-coherent Doppler spectra are finally indexed by frequency in the Doppler dimension. .

[0047] Preferably, the step S4 specifically includes the following steps:

[0048] First, 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. This allows the Doppler spectrum values ​​of multiple base stations to be quickly superimposed, ultimately completing Doppler detection.

[0049] Search range for velocity vector planes and is the theoretical maximum value of the Doppler frequency passing through the system Calculated, Defined as:

[0050] (10)

[0051] The search range of the target in the horizontal and vertical speed directions is determined by formula (9) and is expressed as ;

[0052] Transverse axis 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:

[0053] (11)

[0054] 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;

[0055] For each velocity vector point, the theoretical Doppler frequency value of the velocity vector point at each base station is calculated based on the position of the base station and the movement direction of the target. The calculation formula is:

[0056] (12)

[0057] 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:

[0058] (13)

[0059] The target position 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:

[0060] (14)

[0061] 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:

[0062] (15)

[0063] in, , for each velocity vector point, the corresponding discrete frequency index will be stored in the index matrix In the corresponding position of

[0064] By traversing each point of 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 spectrum value of the velocity vector plane is obtained as:

[0065] (16)

[0066] in, For the Doppler spectrum value of each base station on the velocity vector plane;

[0067] By integrating the spectrum values ​​of all base stations through coherent accumulation, the spectrum of the three base stations after superposition is obtained:

[0068] (17)

[0069] in, .

[0070] Preferably, the step S5 specifically includes:

[0071] Based on the superimposed spectrum of three base stations , extract the maximum value of the spectrum amplitude to obtain the maximum statistic, the expression of the maximum statistic is:

[0072] (18)

[0073] Identify whether the target exists based on the maximum statistic, where Assume no target. For a target hypothesis, the standard testing problem is described as a binary hypothesis test:

[0074] (19)

[0075] in, is complex Gaussian white noise, is the first Single-bit digital signal of each substation, The echo signal received by the substation;

[0076] For statistics , passing a threshold To determine whether the detection problem belongs to still :

[0077] (20)

[0078] Among them, the threshold According to the detection probability and false alarm probability Make adjustments to meet system performance requirements;

[0079] The performance of target detection is and Further assessment, including:

[0080] (twenty one)

[0081] Where, is the probability, Assume no target. For the target hypothesis, is the threshold;

[0082] Finally, through statistics and performance indicators and The analysis can realize the effective evaluation of target existence and complete the Doppler coherent detection of distributed single-bit radar.

[0083] Therefore, the present invention adopts the above-mentioned distributed single-bit radar Doppler coherent detection method, and through reasonable signal processing and optimized spectrum superposition strategy, improves the system's detection capability of the target 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.

[0084] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 This is a flow chart of an embodiment of a distributed single-bit radar Doppler coherent detection method according to the present invention;

[0086] Figure 2 The velocity plane map of the present invention, wherein (a) is a velocity plane map processed coherently, and (b) is a velocity plane map processed non-coherently;

[0087] Figure 3 Parameter relationship diagrams of coherent processing and non-coherent processing of the present invention, wherein (a) is a relationship diagram between false alarm rate and threshold, and (b) is a relationship diagram between detection probability and threshold;

[0088] Figure 4 3. It is the ROC curve diagram of the coherent processing and the non-coherent processing of the present invention. DETAILED DESCRIPTION

[0089] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0090] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" 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 object being described changes, the relative positional relationship may also change accordingly.

[0091] Example

[0092] See also Figure 1-4 The present invention provides a distributed single-bit radar Doppler coherent detection method, comprising the following steps:

[0093] Step S1: Using 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 for data transmission, while the central station directly retains the multi-bit signal received by the base station without transmitting data. Specifically, the method includes:

[0094] Consider a distributed radar system consisting of three radar base stations performing transmission and reception, and a moving target. In this system, the transmitted signal is assumed to be known, and a hybrid sampling method using single-bit sampling at the outstations and multi-bit sampling at the central station is employed. The outstations perform single-bit quantization on the received signal, obtaining a single-bit signal, while the central station retains the received multi-bit signal. Because the distributed radar base stations are located at different locations, their distances and angles from the target vary. Consequently, the received echo signals exhibit differences in delay, Doppler frequency, and reflection coefficient. These differences must be fully accounted for in signal processing to accurately estimate the target's Doppler parameters and optimize system performance.

[0095] After sampling and discretization, the radar transmission signal is expressed as , taking the linear frequency modulation LFM signal as an example, The transmitted signal of a base station is expressed as:

[0096] (1)

[0097] 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;

[0098] 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:

[0099] (2)

[0100] in, is the speed of light;

[0101] Assume that The target radial velocity of each base station is , No. The Doppler frequency of a base station is expressed as:

[0102] (3)

[0103] in, is the wavelength of the transmitted signal;

[0104] Under the influence of Doppler frequency and time delay, the The target echo signal received by each base station is expressed as:

[0105] (4)

[0106] in, , is the index of the Doppler dimension, For the The target reflection coefficient of each base station, is the pulse repetition time, is the total number of sampling points for a pulse repetition time, is the number of pulses;

[0107] 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:

[0108] (5)

[0109] in, , is a symbolic function, and represent the real and imaginary parts of the signal respectively;

[0110] 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:

[0111] (6)

[0112] 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.

[0113] This hybrid sampling method of single-bit sampling at substations and multiple bits at the central station 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.

[0114] 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:

[0115] Matched filtering is a method widely used in distributed radar to enhance target signals 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 first The matched filter output of each base station is:

[0116] (7)

[0117] 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, matched filter output is a size of The matrix (corresponding to the total number of sampling points in the range dimension and the number of pulses in the Doppler dimension) extracts the part of the received signal that matches the transmitted signal.

[0118] Perform fast Fourier transform (FFT) processing on the Doppler dimension to obtain the The Doppler spectrum of a base station is expressed as:

[0119] (8)

[0120] in, , It is a fast Fourier transform processing operation, which means extracting spectrum information in the Doppler frequency dimension.

[0121] Step S3: Based on the Doppler spectrum obtained after matched filtering, a coherent Doppler spectrum and a non-coherent Doppler spectrum are obtained respectively according to whether the phase information is retained. The coherent Doppler spectrum is directly superimposed, while the non-coherent Doppler spectrum extracts the maximum value of the Doppler spectrum of each base station. Specifically including:

[0122] 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 achieve signal energy accumulation, thereby improving the energy concentration of the target signal. Therefore, the coherent Doppler spectrum is directly expressed as the Doppler spectrum after matched filtering .

[0123] 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:

[0124] (9)

[0125] 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.

[0126] Step S4, in the processing of special spatial points, that is, the position points 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. After the discrete weights corresponding to the Doppler frequency are pre-arranged, 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, thereby realizing the target Doppler coherent detection of the distributed single-bit radar. Specifically including:

[0127] First, the velocity vector plane is divided and traversed according to a predefined velocity search range and resolution. The goal is to detect the target's velocity information by traversing all possible velocity vector points in the velocity vector plane and combining them with discrete Doppler spectrum values ​​for weighted superposition and coherent accumulation. To achieve this goal, the search range and resolution of the velocity vector plane must be defined. During the traversal process, a discrete weight index matrix corresponding to the Doppler frequency is established. This allows for rapid superposition of Doppler spectrum values ​​from multiple base stations, ultimately completing Doppler detection.

[0128] Search range for velocity vector planes and is the theoretical maximum value of the Doppler frequency passing through the system Calculated, Defined as:

[0129] (10)

[0130] The search range of the target in the horizontal and vertical speed directions is determined by formula (9) and is expressed as ;

[0131] Transverse axis 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:

[0132] (11)

[0133] 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;

[0134] For each velocity vector point, the theoretical Doppler frequency value of the velocity vector point at each base station is calculated based on the position of the base station and the movement direction of the target. The calculation formula is:

[0135] (12)

[0136] 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:

[0137] (13)

[0138] 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:

[0139] (14)

[0140] 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:

[0141] (15)

[0142] in, , for each velocity vector point, the corresponding discrete frequency index will be stored in the index matrix In the corresponding position of

[0143] By traversing each point of 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 spectrum value of the velocity vector plane is obtained as:

[0144] (16)

[0145] in, For the Doppler spectrum value of each base station on the velocity vector plane;

[0146] By integrating the spectrum values ​​of all base stations through coherent accumulation, the spectrum of the three base stations after superposition is obtained:

[0147] (17)

[0148] in, The above method optimizes the calculation process by using discrete index matrix, which greatly reduces the calculation complexity while ensuring accuracy.

[0149] Step S5: Calculate the maximum value of the velocity plane to obtain the maximum statistics under the H0 hypothesis and the H1 hypothesis respectively. TAnd use this statistic to evaluate the target's existence and realize Doppler detection. Specifically include:

[0150] Based on the superimposed spectrum of three base stations , extract the maximum value of the spectrum amplitude to obtain the maximum statistic, the expression of the maximum statistic is:

[0151] (18)

[0152] Identify whether the target exists based on the maximum statistic, where Assume no target. For a target hypothesis, the standard testing problem is described as a binary hypothesis test:

[0153] (19)

[0154] in, is complex Gaussian white noise, is the first Single-bit digital signal of each substation, The echo signal received by the substation;

[0155] For statistics , passing a threshold To determine whether the detection problem belongs to still :

[0156] (20)

[0157] Among them, the threshold According to the detection probability and false alarm probability Make adjustments to meet system performance requirements;

[0158] The performance of target detection is and Further assessment, including:

[0159] (twenty one)

[0160] Where, is the probability, Assume no target. For the target hypothesis, is the threshold;

[0161] Finally, through statistics and performance indicators and The analysis can realize the effective evaluation of target existence and complete the Doppler coherent detection of distributed single-bit radar.

[0162] Combined with attachment Figure 1 , the specific implementation steps of the present invention are described as follows:

[0163] 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 the central station that receives multi-bit signals, and the second and third base stations are the substations that receive 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 -35 dB.

[0164] 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.

[0165] In this simulation experiment, the radar signal is set to LFM signal:

[0166] ;

[0167] Get the first The receiving signal of each substation is:

[0168] ;

[0169] The single-bit digital signal obtained by quantization is:

[0170] .

[0171] Step S2: Use the obtained single-bit and multi-bit signals 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 based on the matched filtering results of the signal model to extract the Doppler spectrum of the target. .

[0172] Step S3: obtaining a coherent Doppler spectrum and a non-coherent Doppler spectrum respectively according to whether the phase information is retained.

[0173] 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 utilized 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. This position corresponds to the true velocity vector of the target, thus realizing Doppler coherent detection, such as Figure 2 shown. Figure 2 The velocity plane maps of coherent processing and non-coherent processing are plotted in Figure 1. The black △ represents the true value of the target velocity [-5, -10], and the red × represents the estimated value. Coherent Doppler detection combines phase information to highly concentrate the signal energy at the velocity vector point corresponding to the target, forming a relatively clear peak in the velocity plane, as shown in Figure 1. Figure 2 (a) The peak position marked in red. Figure 2 (b) Non-coherent Doppler detection, because it doesn't utilize the signal's phase information, results in a more dispersed signal energy distribution across the velocity plane. The target peak is less pronounced than with coherent methods, and background noise appears more pronounced. This dispersed energy distribution degrades target detection performance, especially under low signal-to-noise ratio conditions. Therefore, coherent methods significantly outperform non-coherent methods in target localization accuracy and noise suppression, demonstrating higher detection precision and robustness.

[0174] Step S5: Based on the signal model established, the simulation finally generates the signal-to-noise ratio of -35dB. Detection probability of single-bit Doppler detection after Monte Carlo simulation experiments and false alarm rate As the threshold changes, such as Figure 3 As shown. Figure 3 As shown in (a), coherent Doppler detection exhibits a significant performance advantage over non-coherent Doppler detection. In the comparison of false alarm rates as the threshold changes, coherent detection (red curve) reduces the false alarm probability more quickly than non-coherent detection (blue curve). As the threshold increases, the false alarm probability of coherent detection decreases more steeply, indicating its ability to suppress noise and interference within the threshold range. Figure 3 As shown in (b), coherent detection maintains a high detection probability at low thresholds, demonstrating strong target acquisition capabilities. Even as the threshold increases, coherent detection performance degrades slowly, maintaining excellent 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 low false alarm probability conditions, reflecting its excellent performance in target detection tasks. Overall, the performance of coherent Doppler detection is better. Figure 3 and Figure 4 Both reflect the strong robustness and anti-interference ability of coherent detection to target signals.

[0175] Therefore, the present invention adopts the above-mentioned distributed single-bit radar Doppler coherent detection method, and through reasonable signal processing and optimized spectrum superposition strategy, improves the system's detection capability of the target and improves the Doppler detection accuracy under low signal-to-noise ratio conditions.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions 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 the possible location points of the target corresponding to the delay index, the target velocity vector plane is traversed, 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 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 2, 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 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.

4. The distributed single-bit radar Doppler coherent detection method according to claim 3, 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 4, 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 5, 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 evaluation, including: （21） In the formula, is the probability, Assume no target. For the target hypothesis, is the threshold value; 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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