Multi-station external emitter radar target positioning method based on TDOA-RRSS

Abstract

The present invention discloses a multi-station external radiation source radar target positioning method based on TDOA-RRSS, which mainly solves the problems of the existing technology that it is difficult to uniquely locate the target, the calculation is complex, and the radar software and hardware requirements are high. The solution includes: 1) receiving the echo of the external radiation source radar station; 2) using the reference signal to perform pulse compression processing; 3) using the one-dimensional CA-CFAR method to estimate the noise power, calculate the detection threshold and detect whether the target exists; 4) after completing the detection of all stations, calculate the distance value between the target and the radar station containing the fuzzy solution according to the TDOA equation; 5) extracting the unit average constant false alarm rate detection amplitude result to establish an RRSS expression to determine whether the distance value calculated in the previous step is true; 6) after screening out the true distance value, using TDOA calculation to obtain a unique positioning result to complete the positioning. The present invention can eliminate fuzzy solutions with low threshold and low complexity to achieve target positioning.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar target positioning, and further relates to an improved target positioning method based on a time difference of arrival positioning method, specifically a multi-station off-site radiation source radar target positioning method based on TDOA-RRSS, which can be used for multi-station off-site radiation source radar target detection and positioning processing. Background Art

[0002] Multi-station exoplanet radars typically employ a layout of three or more receiving stations, passively receiving reflected echoes from targets and performing signal processing for target detection, location, and tracking. Because they require no high-power transmitters or power supplies, they offer advantages such as small size, light weight, and flexible deployment, attracting considerable attention in recent years. Due to their separate transmitter and receiver architecture, multi-station exoplanet radars often employ Time Difference of Arrival (TDOA) for target location, achieving high positioning accuracy with low hardware requirements. This technique exploits the time difference between the time it takes for an exoplanet radar signal to illuminate a target and reflect back into the radar path, and the time it takes for the signal to be directly transmitted to the radar path. With multiple receiving stations, all time difference measurements can be combined to solve the (x, y, z) equation for the target's position. This equation is solvable when the number of radar stations exceeds three. However, the quadratic equations in this positioning technique often contain multiple solutions, resulting in significant uncertainty. Therefore, additional information is required to uniquely locate the target, leading to the development of numerous improved TDOA-based positioning methods.

[0003] Xi'an University of Posts and Telecommunications has disclosed a positioning method based on RSS and TDOA measurements in its patent application, "Positioning Method Based on RSS and TDOA Measurements in Non-Line-of-Sight Environments" (Application Number: CN201811528200.9, Application Publication Number: CN110536410B). The method mainly solves the problem of passive positioning of wireless signal emitters in non-line-of-sight environments. Although this method can achieve good positioning performance under low complexity and does not require non-line-of-sight deviation information, solving the problem of passive positioning of emitters in non-line-of-sight environments, it still has the following shortcomings: the RSS (received signal strength) positioning equation assumes the amplitude of the emitter's transmitted signal is known. However, in the multi-station off-site emitter radar target positioning, the amplitude of the target's secondary reflection signal cannot be determined, so it is impossible to establish an RSS equation related to distance. In addition, the joint solution expands the dimension of the calculation matrix, making the solution process complicated. In their paper “Multi-platform Time Difference Positioning Method Based on RSS Assistance” (10.16337 / j.1004-9037.2020.06.006.), Liu Anfei et al. proposed a method for locating the source of radio signal transmission by using the time difference between the radio signal reaching different monitoring nodes. Although this method can improve positioning accuracy while eliminating ambiguous solutions, due to the use of the RSS-then-TDOA calculation process, at least four receiving stations are required to achieve the above results. In addition, the repeated changes in the position of the receiving station not only place high demands on the mobility and site error of the receiving station, but also reduce its detection performance for maneuvering targets. In their paper "EKF-based Satellite-Ground Collaborative Direction Finding Time Difference Positioning Algorithm" (10.3969 / J.ISSN.1672-7274.2024.04.002), Wang Zhe et al. proposed a satellite-ground collaborative positioning method using arrival angle and arrival time difference. This method can filter the arrival angle and time difference measurement parameters and provide the EKF recursive formula under this model. However, this method relies on the arrival angle measurement results of the target. According to analysis, the positioning accuracy is mainly limited by the angle measurement error. If the angle measurement accuracy is to be improved, the volume and weight of the radar will increase, and its original advantages will no longer exist.

[0004] In recent years, improved positioning methods based on TDOA generally have the problem of introducing multiple solutions, resulting in ambiguous positioning results and the inability to determine the specific location of the target; the TDOA joint estimation algorithm that introduces additional information increases the dimension of the calculation matrix and requires the radar to measure the target angle or speed (such as DOA direction of arrival and FDOA relative frequency difference), which puts forward certain requirements for radar hardware and processing algorithms, resulting in an increase in radar volume, weight, and power consumption, which is not conducive to the miniaturization and lightweighting of the radar. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned existing technologies and propose a multi-station external emitter radar target positioning method based on the signal strength ratio TDOA-RRSS, which is used to solve the problem that TDOA positioning technology is difficult to uniquely locate the target, and the improved algorithm of the existing technology that introduces information such as RSS is complex in calculation and has high requirements on radar software and hardware.

[0006] The idea of ​​implementing the present invention is: based on the traditional received signal strength RSS expression, combined with the attenuation law of the external radiation source radar target echo, the received signal strength ratio RRSS (Ratio of Received Signal Strength) equation is constructed, and the constraint equation of the distance from the target to the radar station is obtained in the form of a quotient. The uncertainty of the distance value is exactly the reason why the result is ambiguous during the TDOA analysis process; therefore, the intermediate result of the TDOA calculation is introduced into the RRSS constraint equation, the authenticity coefficient of the intermediate value is obtained, and the target is determined to exist when it is less than a certain range; since the RRSS equation does not require known transmitted signal power, nor does it require prior information such as the distance between the target and the radiation source, it has low requirements for radar hardware and strong feasibility. In addition, the present invention does not expand the original TDOA equation for joint solution, but finds key variables and constrains them, thereby effectively controlling the amount of calculation, thereby effectively reducing the threshold of radar hardware and software, and solving the problem of high computational complexity of existing algorithms, eliminating fuzzy solutions with low threshold and low complexity, and realizing target positioning.

[0007] The present invention achieves the above-mentioned purpose by the following specific steps:

[0008] (1) Establish a multi-station radar echo model including a radiation source, a target to be measured, and N external radiation source radar stations, where N ≥ 3. The signal emitted by the radiation source illuminates the target to be measured, and the N external radiation source radar stations receive the radiation source signal reflected by the target. At the same time, the radar reference antenna receives the signal directly emitted by the radiation source to the radar station. The signal directly emitted by the radiation source to the radar is called the direct wave signal, and the signal reflected by the target is called the target echo.

[0009] (2) Input the target echo received by the i-th external radiation source radar station, i = 1, 2...N; initialize, set i = 1;

[0010] (3) Using the radiation source signal received by the radar reference antenna as a reference signal, pulse compression processing is performed on the target echo signal received by the i-th external radiation source radar station to obtain a pulse compression result;

[0011] (4) Use the one-dimensional unit average constant false alarm rate detection CA-CFAR method to estimate the noise power, calculate the detection threshold and detect whether the target exists; if the target exists, extract and record the target parameters and continue to step (5); otherwise, set i = i + 1 and return to step (3);

[0012] (5) Determine whether i is equal to N. If so, it means that all site detections have been completed and continue to step (6); otherwise, set i = i + 1 and return to step (3);

[0013] (6) Using the target parameters, calculate the distance between the target and the radar station with the fuzzy solution according to the TDOA equation;

[0014] (7) Extract the signal amplitude exceeding the detection threshold in step (4) to establish an RRSS expression, and use it to determine whether the distance value calculated in step (6) is true, and select the distance value that meets the RRSS condition as the final distance value ||X'||;

[0015] The RRSS expression is as follows:

[0016]

[0017] Among them, A i is the target echo signal amplitude measured by the i-th radar receiving station, G r is the gain value of the signal processing part of the antenna of the external radiation source radar station to the echo power, σ is the radar scattering cross section of the target, P t is the emission power of the radiation source, T x is the distance from the radiation source to the target, R i is the distance from the target to the i-th radar receiving station, and π represents pi;

[0018] The variable R related to the target coordinates in the above formula i The remaining parameters are considered as constant ρ, and the simplified expression is A i =ρ / R i ; Calculate the ratio of the amplitude measured by the i-th radar receiving station to the j-th radar receiving station, where j = 1, 2...N and i ≠ j, and obtain the RRSS result w ij :

[0019]

[0020] Solving the above equation yields the constraint equation for the distance value:

[0021]

[0022] Among them, the target coordinates are X=(x,y,z), R xi With R xj denote the coordinates of the i-th and j-th radar stations, respectively. a and b are two intermediate variables in the TDOA calculation process.

[0023] (8) Using the final distance value ||X'||, a unique positioning result is obtained through TDOA calculation to complete the target positioning.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] First, an innovative RRSS calculation method is proposed for the formula of target signal strength received by multi-station external radiation source radar. Compared with the traditional RSS algorithm, the method of the present invention eliminates the interference term of multi-station echo strength, so that the result is only related to the distance from the target to the radar, and realizes the constraint condition of obtaining the target position without any prior information. It overcomes the defect of existing solutions that require prior information, effectively lowers the radar hardware threshold, and is more feasible.

[0026] Second, in order to address the shortcomings of the conventional TDOA-based joint positioning algorithm in terms of complex calculations, the present invention designs an implementation process that first completes the low-dimensional calculation of TDOA key parameters, then introduces RRSS constraints to screen the correct parameters, and finally outputs the positioning results. Therefore, it can effectively reduce the matrix calculation dimension, thereby reducing the computational complexity and improving the computational efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an overall implementation flow chart of the method of the present invention;

[0028] Figure 2 is the echo model diagram in the method of the present invention;

[0029] Figure 3 Schematic diagram of unit average constant false alarm detection used in the present invention;

[0030] Figure 4 This is a simulation result diagram of continuous positioning of radar targets with multiple external radiation sources using the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0032] Example 1: Reference Figure 1 The present invention proposes a multi-station external emitter radar target positioning method based on TDOA-RRSS. The method establishes an expression for the quotient of the received signal strength and the RRSS target echo amplitude, and uses the distance between the target and the radar station in the TDOA time difference positioning method as the intermediate value for screening. After determining the final correct distance value, the target coordinates are calculated. The specific implementation steps of the method include the following:

[0033] Step 1. Establish a multi-station radar echo model including a radiation source, a target to be measured, and N external radiation source radar stations, where N ≥ 3. The signal emitted by the radiation source illuminates the target to be measured, and the N external radiation source radar stations receive the radiation source signal reflected by the target. At the same time, the radar reference antenna receives the signal directly emitted by the radiation source to the radar station; the signal directly emitted by the radiation source to the radar is called the direct wave signal, and the radiation source signal reflected by the target is called the target echo; the target echo refers to the echo data containing target information.

[0034] Step 2. Input the target echo received by the i-th external radiation source radar station, i = 1, 2...N; initialize, set i = 1;

[0035] Step 3. Using the radiation source signal received by the radar reference antenna as a reference signal, pulse compression processing is performed on the target echo signal received by the i-th external radiation source radar station to obtain a pulse compression result. In this embodiment, the pulse compression processing is implemented by performing the following operations using the received direct wave signal and the target echo:

[0036] (3.1) De-noising the direct wave signal to improve the direct wave signal-to-noise ratio;

[0037] (3.2) Perform fast Fourier transform on the echo signal, find the conjugate, and then multiply it with the Fourier transform result of the reference signal;

[0038] (3.3) Perform inverse Fourier transform on the multiplication result obtained in step (3.2) to complete frequency domain pulse compression and obtain the pulse compression result.

[0039] Step 4. Use the one-dimensional unit average constant false alarm rate detection CA-CFAR method to estimate the noise power, calculate the detection threshold and detect whether the target exists; if the target exists, extract and record the target parameters and continue to step 5; otherwise, set i = i + 1 and return to step 3.

[0040] The target parameters in this embodiment include at least the current bistatic delay information and amplitude information of the target. The one-dimensional unit average constant false alarm rate detection algorithm performs the following operations on the pulse compressed signal:

[0041] (4.1) Estimate the noise power based on a fixed-length reference unit;

[0042] (4.2) Calculate the target detection threshold value based on the preset false alarm probability;

[0043] (4.3) Perform one-dimensional constant false alarm detection on the echo signal amplitude and threshold value to determine whether there is a target.

[0044] Step 5. Determine whether i is equal to N. If so, it means that all site detections have been completed and continue to step 6; otherwise, set i = i + 1 and return to step 3;

[0045] Step 6. Using the target parameters, calculate the distance between the target and the radar station with the fuzzy solution according to the TDOA equation. The implementation steps are as follows:

[0046] (6.1) Set the coordinates in the Earth-centered Earth-fixed coordinate system, and take the radiation source as the origin of the coordinate system. Let the coordinates of the radiation source be (x t ,y t ,z t )=(0,0,0), the target coordinates are X=(x,y,z), and the coordinates of the i-th radar station are R xi =(x i ,y i ,z i ), construct the following TDOA equation:

[0047]

[0048] Where c represents the speed of light, τ i It represents the bistatic time difference from the target to be measured to the i-th radar station,

[0049] B i =|(x t ,y t ,z t )-(x i ,y i ,z i )| represents the distance from the radiation source to the i-th radar station;

[0050] Matrixing the TDOA equation yields:

[0051] AX=k+c||X||,

[0052] in,

[0053] (6.2) Find the generalized inverse of A, let a=(A T A) -1 A T k,b=(A T A) -1 A T c. After simplification, we get the vector ||X|| of the distance between the target and the radar station:

[0054]

[0055] Step 7. Extract the signal amplitude exceeding the detection threshold in step 4 to establish an RRSS expression, and use this to determine whether the distance value calculated in step 6 is true. In this embodiment, an RRSS constraint equation is established, and the distance value obtained in step 6 is substituted into the constraint equation to determine whether the equation is equal, that is, whether both sides of the equation are equal. If so, the distance value is true and recorded; otherwise, the distance value is discarded. Thus, the distance value that meets the RRSS condition is selected as the final distance value ||X'||.

[0056] The RRSS expression is as follows:

[0057]

[0058] Among them, A i is the target echo signal amplitude measured by the i-th radar receiving station, G r is the gain value of the signal processing part of the antenna of the external radiation source radar station to the echo power, σ is the radar scattering cross section of the target, P t is the emission power of the radiation source, T x is the distance from the radiation source to the target, R i is the distance from the target to the i-th radar receiving station, and π represents pi;

[0059] The variable R related to the target coordinates in the above formula i The remaining parameters are considered as constant ρ, and the simplified expression is A i =ρ / R i ; Calculate the ratio of the amplitude measured by the i-th radar receiving station to the j-th radar receiving station, where j = 1, 2...N and i ≠ j, and obtain the RRSS result w ij :

[0060]

[0061] Solving the above equation yields the constraint equation for the distance value:

[0062]

[0063] Among them, the target coordinates are X=(x,y,z), R xi With R xj denote the coordinates of the i-th and j-th radar stations, respectively. a and b are two intermediate variables in the TDOA calculation process.

[0064] Step 8. Use the final distance value ||X'|| to obtain a unique positioning result through TDOA calculation to complete the target positioning. The positioning result is specifically the target coordinate X calculated according to the following formula:

[0065] X=a+b||X'||.

[0066] Example 2: Reference Figure 1-3 The overall implementation steps of this embodiment are the same as those of the first embodiment. The implementation process of the present invention will now be further described in detail with reference to specific examples.

[0067] Step A: Establish a multi-station radar echo model.

[0068] Reference Figure 2 , the echo model of the present invention is further described in detail.

[0069] When a signal from a single emitter illuminates a target (for example, a flying target), N external emitter radars (N ≥ 3) can receive the signal reflected by the target. Simultaneously, the signal directly from the emitter to the radar station is also received by the radar reference antenna. The signal directly from the emitter to the radar is called the direct wave signal, while the signal reflected by the target is called the target echo.

[0070] Step B. Receive the i-th radar echo signal from N stations and perform pulse compression;

[0071]

[0072] Among them, X i (t) represents the pulse compression result of the echo signal received by the i-th external radiation source radar station, α i is the amplitude of the pulse pressure result, Λ(·) is the autocorrelation function of the transmitted signal, T c is the observation time length, R tr_i is the target echo path, expressed as the sum of the distance from the transmitter to the target and the distance from the target to the i-th radar. In the remaining symbols, t is the time dimension after pulse compression, c is the speed of light, and exp represents the exponential operation with base e.

[0073] Step C: Detect the target according to the following steps:

[0074] (c1) Taking a fixed-length reference unit as a benchmark, the estimated noise power is:

[0075]

[0076] Among them, Z ca (t) is X i The noise power estimate of the signal at (t), L is the reference unit length, It means that the signal is accumulated from l=1 to L.

[0077] (c2) According to the specified false alarm probability, the target detection threshold is calculated as:

[0078]

[0079] Where T(t) is X i The target detection threshold at (t), p fa Represents the false alarm rate, which can be 10 -5 Typical value.

[0080] (c3) Compare the echo amplitude of the unit to be detected with the threshold to determine whether there is a target:

[0081]

[0082] The above formula shows that when X i When (t) is greater than T(t), assume that H1 is true, that is, there is a target; and when X i When (t) is less than T(t), assume that H0 is true, that is, there is no target.

[0083] (c4) If a target exists, record the target amplitude and delay information. Otherwise, receive the i+1th radar echo signal from N stations and execute step B again.

[0084] If there is a target, record the target echo signal amplitude measured by the i-th radar receiving station. The expression is as follows:

[0085]

[0086] Among them, G r is the gain value of the external radiation source radar station antenna and signal processing part to the echo power, σ is the RCS of the target, P t is the emission power of the radiation source, T x is the distance from the radiation source to the target, R i is the distance from the target to the i-th radar receiving station, and π represents the circumference of a circle. i is a variable related to the target coordinates, and the other parameters can be regarded as constants, so the above formula can be simplified to A i =ρ / R i , and the ratio of the amplitudes measured by each radar station, that is, the RRSS result, can be expressed as:

[0087]

[0088] Among them, w ij is the relative signal intensity ratio measured by RRSS.

[0089] The target delay measurement result is:

[0090]

[0091] Among them, τ i is the relative time delay information of the target echo measured by the i-th radar receiving station.

[0092] Step D: After all stations have completed target detection and have found the target, calculate the target position:

[0093] (d1) With the radiation source as the origin of the coordinate system (x t ,y t ,z t )=(0,0,0), establish a Cartesian three-dimensional rectangular coordinate system, set the target coordinates to be X=(x,y,z), and the coordinates of the i-th radar station to be R xi =(x i ,y i ,z i ), the target TDOA measurement equation for the i-th site can be listed as:

[0094] cτ i =T x +R i -B i

[0095] Among them, T x =|(x t ,y t ,z t )-(x,y,z)| is the distance from the radiation source to the target, R i =|(x,y,z)-(x i ,y i ,z i )| is the distance from the target to the i-th radar station, B i =|(x t ,y t ,z t )-(x i ,y i ,z i )| represents the distance from the radiation source to the i-th radar station.

[0096] Furthermore, after simplification of the above equation, we can get the following expression:

[0097]

[0098] (d2) Matrix the measurement equation:

[0099] AX=k+c||X||

[0100] in,

[0101] (d3) Solving unknown positioning parameters

[0102] When N≠3, A cannot be inverted. To ensure the applicability of the algorithm to different conditions, the generalized inverse of A in the above formula is obtained to obtain the expression of the target coordinates:

[0103] X=(A T A) -1 A T (k+c||X||)

[0104] To simplify the expression, let a=(A T A) -1 A T k,b=(A T A) -1 A T c, then the above formula can be expressed as X=a+b||X||, since ||X||=X T X, square the above equation and simplify it to get:

[0105] (b T b-1)||X|| 2 +(b T a+a T b)||X||+a T a=0

[0106] This is a quadratic equation, and the value of ||X|| can be solved to be:

[0107]

[0108] (d4) Substitute the RRSS result and filter out the remaining solutions that do not meet the requirements in X:

[0109] In the RRSS results, due to w ij is the ratio of the measurement result of the i-th radar station to the measurement result of the j-th radar station. After squaring it and further simplifying it, we can get:

[0110]

[0111] Substitute the calculated result of ||X|| in step (d3) into the above formula. When the equation is established, the target coordinates at this time are determined to be correct. If the equation is not established, the target coordinates at this time are excluded, and the target coordinates are finally obtained:

[0112] X=a+b||X||.

[0113] The positioning method proposed in the present invention establishes an RRSS observation equation. By analyzing the intensity of the target's reflected echo signal, the influence of factors such as the distance from the radiation source to the target is eliminated, and an observation equation related only to the distance from the target to the radar station is obtained. This equation is then used to constrain the TDOA intermediate results, thereby filtering out redundant solutions and finally achieving target positioning with extremely low software and hardware thresholds. The technical solution proposed in this application introduces relative signal amplitude information between multiple stations on the basis of the original TDOA positioning results and filters out fuzzy results, giving full play to the inherent advantages of external radiation source radars, thereby effectively solving the problems of the existing technology requiring known radiation source power, joint angles, and RSS equation calculations, which leads to an expansion of the calculation matrix dimension, an increase in the amount of calculation and the number of receiving stations, the iterative algorithm being susceptible to station site errors, and the adverse effects of high-precision angle measurement on the volume and weight of the radar.

[0114] The advantages of multi-station off-site radars are their maneuverability, flexibility, and high concealment. The TDOA-RRSS positioning method proposed in this application perfectly reflects and enhances the advantages of this system. It does not rely on large-scale antennas to obtain angle information, nor does it require complex calculations to measure the target echo frequency. It can stably and effectively achieve target positioning. Therefore, multi-station off-site radars using this positioning technology have smaller antenna sizes, lower power consumption, and faster positioning speeds, thereby accelerating the deployment of off-site radars on automobiles, small ships, and drones. At the same time, the lower computational requirements effectively increase the system's battery life and significantly expand the practical application range of multi-station off-site radars.

[0115] The effects of the present invention will be further described below in conjunction with simulation experiments.

[0116] 1. Simulation conditions:

[0117] The simulation experiment of the present invention was carried out in a hardware environment with a CPU main frequency of 3.8 GHz, a memory of 16 GB, a graphics card GTX1060, and Windows 10 using Matlab-R2021b software.

[0118] 2. Simulation content:

[0119] In order to fully demonstrate the positioning effect of this method on real targets, we set up a real target trajectory positioning simulation experiment. This experiment was carried out in the ground-fixed geocentric coordinate system, and the real target motion trajectory was input for detection and positioning. The radiation source coordinates were set at the coordinates (2500, 1200, 3900), and the transmission signal was set to a linear frequency modulation signal with a frequency of 1 GHz, a signal bandwidth of 4.2 MHz, and a pulse repetition frequency of 1000 Hz. The simulation setting has a total of 3 radar stations, whose coordinates are (-3000, 4500, 3600), (-2800, 4590, 3390), and (-2500, 4000, 4000). The radar uses a 10 MHz baseband sampling rate, performs target positioning processing every 1 second, and continuously outputs positioning results. The simulation parameters and settings are shown in Table 1:

[0120] Table 1 Simulation parameters and settings

[0121]

[0122] 3. Simulation results:

[0123] The simulation results are as follows Figure 4 As shown in the figure. For a moving target lasting 500 seconds, all three radar stations detected and processed the target, outputting 500 target coordinates. These coordinates were distributed along the target's motion trajectory, demonstrating high positioning stability. This simulation fully demonstrates that the method of the present invention can uniquely and accurately locate real moving targets. It further verifies the feasibility of the method of the present invention for positioning with only three radar stations, utilizing the amplitude and time difference information in the echo signals, with minimal hardware and software requirements.

[0124] The above simulation analysis proves the correctness and effectiveness of the method proposed in the present invention.

[0125] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A multi-station external emitter radar target positioning method based on TDOA-RRSS, characterized in that: An expression for the received signal strength ratio (RSS) of the target echo amplitude is established. The target distance between the target and the radar station in the time difference of arrival (TDOA) method is used as an intermediate value for screening. The target coordinates are then calculated after the final correct distance value is generated. The implementation steps include the following: (1) Establish a multi-station radar echo model including a radiation source, a target to be measured, and N external radiation source radar stations, where N ≥ 3. The signal emitted by the radiation source illuminates the target to be measured, and the N external radiation source radar stations receive the radiation source signal reflected by the target. At the same time, the radar reference antenna receives the signal directly emitted by the radiation source to the radar station. The signal directly emitted by the radiation source to the radar is called the direct wave signal, and the signal reflected by the target is called the target echo. (2) Input the target echo received by the i-th external radiation source radar station, i = 1, 2...N; initialize, set i = 1; (3) Using the radiation source signal received by the radar reference antenna as a reference signal, pulse compression processing is performed on the target echo signal received by the i-th external radiation source radar station to obtain a pulse compression result; (4) Use the one-dimensional unit average constant false alarm rate detection CA-CFAR method to estimate the noise power, calculate the detection threshold and detect whether the target exists; if the target exists, extract and record the target parameters and continue to step (5); otherwise, set i = i + 1 and return to step (3); (5) Determine whether i is equal to N. If so, it means that all site detections have been completed and continue to step (6); otherwise, set i = i + 1 and return to step (3); (6) Using the target parameters, calculate the distance between the target and the radar station with the fuzzy solution according to the TDOA equation; (7) Extract the signal amplitude exceeding the detection threshold in step (4) to establish an RRSS expression, and use it to determine whether the distance value calculated in step (6) is true, and select the distance value that meets the RRSS condition as the final distance value ||X'||; The RRSS expression is as follows: Among them, A i is the target echo signal amplitude measured by the i-th radar receiving station, G r is the gain value of the signal processing part of the antenna of the external radiation source radar station to the echo power, σ is the radar scattering cross section of the target, P t is the radiation source transmission power, T x is the distance from the radiation source to the target, R i is the distance from the target to the i-th radar receiving station, and π represents pi; The variable R related to the target coordinates in the above formula i The remaining parameters are considered as constant ρ, and the simplified expression is A i =ρ / R i ; Calculate the ratio of the amplitude measured by the i-th radar receiving station to the j-th radar receiving station, where j = 1, 2...N and i ≠ j, and obtain the RRSS result w ij : Solving the above equation yields the constraint equation for the distance value: Among them, the target coordinates are X=(x,y,z), R xi With R xj denote the coordinates of the i-th and j-th radar stations, respectively. a and b are two intermediate variables in the TDOA calculation process. (8) Using the final distance value ||X'||, a unique positioning result is obtained through TDOA calculation to complete the target positioning.

2. The method according to claim 1, wherein: The target echo in step (1) refers to echo data containing target information.

3. The method according to claim 1, wherein: The pulse compression processing in step (3) specifically refers to performing the following operations using the received direct wave signal and the target echo: (3.1) De-noising the direct wave signal to improve the direct wave signal-to-noise ratio; (3.2) Perform fast Fourier transform on the echo signal, find the conjugate, and then multiply it with the Fourier transform result of the reference signal; (3.3) Perform inverse Fourier transform on the multiplication result obtained in step (3.2) to complete frequency domain pulse compression and obtain the pulse compression result.

4. The method according to claim 1, wherein: The one-dimensional unit average constant false alarm rate detection algorithm in step (4) is to perform the following operations on the pulse compressed signal: (4.1) Estimate the noise power based on a fixed-length reference unit; (4.2) Calculate the target detection threshold value based on the preset false alarm probability; (4.3) Perform one-dimensional constant false alarm detection on the echo signal amplitude and threshold value to determine whether there is a target.

5. The method according to claim 1, wherein: The target parameters in step (4) refer to the current bistatic delay information and amplitude information of the target.

6. The method according to claim 1, wherein: In step (6), the target parameters are used to calculate the distance between the target and the radar station with the fuzzy solution according to the TDOA equation, as follows: (6.1) Set the coordinates in the Earth-centered Earth-fixed coordinate system, and take the radiation source as the origin of the coordinate system. Let the coordinates of the radiation source be (x t ,y t ,z t )=(0,0,0), the target coordinates are X=(x,y,z), and the coordinates of the i-th radar station are R xi =(x i ,y i ,z i ), construct the following TDOA equation: Where c represents the speed of light, τ i Indicates the bistatic time difference from the target to be measured to the i-th radar station, B i =|(x t ,y t ,z t )-(x i ,y i ,z i )| represents the distance from the radiation source to the i-th radar station; Matrixing the TDOA equation yields: AX=k+c||X||, in, (6.2) Find the generalized inverse of A, let a=(A T A) -1 A T k,b=(A T A) -1 A T c. After simplification, we get the vector ||X|| of the distance between the target and the radar station:

7. The method according to claim 1, wherein: In step (7), it is determined whether the distance value calculated in step (6) is true. Specifically, the RRSS constraint equation is established, the distance value obtained in step (6) is substituted into the constraint equation, and it is determined whether the equation is equal, that is, whether the two sides of the equation are equal; if so, the distance value is true and is recorded, otherwise the distance value is discarded.

8. The method according to claim 1, wherein: The positioning result in step (8) is specifically the target coordinate X calculated according to the following formula: X=a+b||X'||.

Images