Short baseline synthetic aperture passive positioning method and system based on MUSIC spectrum estimation

Abstract

The invention discloses a short baseline synthetic aperture passive positioning method and system based on MUSIC spectrum estimation, and mainly solves the problem of large positioning error and frequency estimation error caused by residual frequency deviation in the prior art. According to the implementation scheme, the method comprises the steps that a geometric scene comprising a reconnaissance plane, two short baseline antennas and an unknown radiation source is built; obtaining signals of the radiation source received by the two short baseline antennas on the reconnaissance plane according to the geometric scene; performing down-conversion and correlation method processing on the received signal to obtain a single-frequency signal, and performing noise adding and sampling processing on the single-frequency signal to obtain discrete data; performing MUSIC spectrum estimation on the discrete data to obtain a frequency estimation value; and calculating the coordinates of the radiation source according to the frequency estimation value. Through the MUSIC spectrum estimation algorithm, the original positioning problem is converted into the frequency estimation problem of the signal to be measured, the spectrum estimation error can be reduced, the reliability of the model is improved, the high-precision, high-real-time and high-robustness frequency estimation of the single-frequency short signal is realized, and the method can be used for a discontinuous short signal sequence unknown signal source with a short baseline and without periodicity.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and further relates to a synthetic aperture passive positioning method and system, which can be used for an unknown signal source that transmits non-periodic discontinuous extremely short pulses or continuous wave signals. Background Art

[0002] In the field of synthetic aperture passive location technology, traditional implementations typically use a single-antenna radar system mounted on a reconnaissance platform. This system passively receives electromagnetic signals emitted by a target emitter, extracts signal segments equal to the pulse width at specific pulse repetition intervals, and constructs the emitter's characteristic parameters using frequency, range, and azimuth. This system then demodulates the baseband signal to obtain a pure single-frequency signal. However, due to the lack of a collaborative working mechanism between the transmitter and receiver, accurate carrier frequency parameters are difficult to obtain in practical applications. This inherent non-cooperative nature of the system can lead to uncorrected frequency deviations, which in turn affects the accuracy of synthetic aperture imaging.

[0003] In his published paper “Synthetic Aperture Passive Positioning Method and System”, Wang Yuqi disclosed a synthetic aperture passive positioning method and system. During the positioning process, by analyzing the influence of the higher-order terms of the slant range history on the distance positioning error, an approximate expression for the positioning error based on the matching of the second-order terms was proposed, and a method for optimizing the synthetic aperture length was given. During signal processing, the synthetic aperture technology is used to perform coherent accumulation on the received signal, thereby improving the positioning accuracy and resolution. Although this method can solve the problem of distance positioning error caused by the higher-order terms of the slant range history in traditional passive positioning methods, it overcomes the shortcomings of the existing technology in that it is difficult to balance positioning accuracy and resolution, and achieves high-precision positioning of the radiation source. However, since it requires a long time to coherently accumulate the signal, and the airborne platform needs to fly over the zero-crossing point of the angle with the target, the timeliness and usage scenarios of the positioning method are limited.

[0004] Patent document CN202210135040.1 discloses a "passive synthetic aperture radiation source positioning method based on phase differential interferometry processing." It performs phase differentiation on two received signals, extracts the differential signal phase after low-pass filtering, and performs linear fitting. The time corresponding to zero phase is recorded, and the azimuth distance is obtained by combining it with the flight speed of the positioning platform. The frequency corresponding to the zero phase moment of the received signal of one antenna in the interferometer is extracted, which is the residual frequency deviation. The received signal of a single antenna is demodulated, and a matched filter with different frequency modulation slopes is used to search and estimate the Doppler modulation frequency to obtain the range distance. The final positioning is achieved by combining the azimuth distance. This method can accurately estimate the residual frequency and azimuth distance, and can reduce the passive synthetic aperture radiation source positioning from a two-dimensional search to a one-dimensional search, reducing the computational complexity. However, this method is susceptible to factors such as multipath effects and electromagnetic interference in complex electromagnetic environments, resulting in increased positioning errors. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of the above-mentioned existing technologies and propose a short-baseline synthetic aperture passive positioning method and system based on MUSIC spectrum estimation assistance, so as to improve the estimation accuracy of signal frequency by using the MUSIC spectrum estimation method to measure the frequency of the signal from which the residual frequency offset has been eliminated, thereby achieving high-precision spectrum estimation and real-time positioning of the radiation source.

[0006] To achieve the above objectives, the implementation scheme of the present invention includes the following:

[0007] 1. A short-baseline synthetic aperture passive positioning processing method based on MUSIC spectrum estimation, characterized in that the frequency measurement of a signal from which residual frequency offset has been eliminated is performed using the MUSIC method, comprising:

[0008] Build a geometric scene consisting of a reconnaissance aircraft, two short baseline antennas, and an unknown radiation source;

[0009] According to the geometric scene, the signals of unknown radiation sources received by the two short baselines are obtained. and

[0010] To receive the signal and Perform down-conversion and correlation processing to obtain a single-frequency signal s coupled with the distance parameter c (t m ), the single frequency signal is processed to obtain a noise signal And sample it to obtain discrete data x(n);

[0011] The frequency of discrete data x(n) is estimated by MUSIC spectrum estimation method to obtain the estimated value

[0012] According to the frequency estimate The coupling relationship with the distance parameter is used to solve the coordinates of the radiation source.

[0013] Furthermore, the frequency of the discrete data x(n) is estimated by the MUSIC spectrum estimation method to obtain the estimated value Its implementation includes:

[0014] 1) For discrete data x(n), calculate its autocorrelation matrix R;

[0015] 2) Perform eigenvalue decomposition on the autocorrelation matrix R and arrange the eigenvectors corresponding to the eigenvalues ​​to obtain the signal subspace and noise subspace;

[0016] 3) Define the direction vector a(f), and obtain the MUSIC pseudo-spectrum from the direction vector and the noise subspace;

[0017] 4) Set the initial spectrum estimation interval to [f min ,f max ], discretize the search space with a uniform sampling interval △f0 within this interval to generate a set of discrete frequency points;

[0018] 5) By calculating the pseudo-spectrum amplitude of each frequency point, the frequency corresponding to the maximum amplitude is determined to be the final estimated frequency.

[0019] 2. A short-baseline synthetic aperture passive positioning processing system, comprising:

[0020] The scenario construction module is used to build a geometric scenario including an unknown radiation source, a reconnaissance aircraft and its two short baseline antennas to locate the unknown source;

[0021] Signal receiving module: used to receive unknown radiation source signals through the dual short baseline model;

[0022] Correlation processing module: used to perform down-conversion and correlation processing on the received signal to obtain a single-frequency signal coupled with the distance parameter, perform noise processing on the single-frequency signal to obtain a noisy signal, and then sample the signal to obtain discrete signal data;

[0023] MUSIC spectrum frequency estimation module: used to perform frequency estimation on discrete signal data using the MUSIC spectrum estimation method, obtain frequency estimation values, and calculate the coordinates of unknown radiation sources based on the obtained frequency estimation values.

[0024] 3. A synthetic aperture spectrum computer-readable storage medium, characterized in that the synthetic aperture spectrum computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the above-mentioned short-baseline synthetic aperture passive positioning method based on MUSIC spectrum estimation.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] First, when performing synthetic aperture passive positioning, the present invention uses a reconnaissance aircraft equipped with two short-baseline antennas to locate the unknown radiation source signal, and performs correlation processing on the two received signals to eliminate the residual frequency offset. This not only reduces the impact of the residual frequency offset caused by inaccurate carrier frequency estimation of the radiation source's transmitted signal, but also reduces the computational complexity.

[0027] Secondly, the present invention adopts a short baseline positioning method to obtain discrete data corresponding to the straight-line distance, and transforms the original positioning problem into a frequency estimation problem of the signal to be measured through the MUSIC spectrum estimation algorithm, thereby realizing high-precision, high real-time and high-robustness frequency estimation of non-periodic and non-continuous single-frequency short signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the implementation of the short-baseline synthetic aperture passive positioning processing method of the present invention;

[0029] Figure 2 It is the short baseline passive positioning geometric scene graph in the method of the present invention;

[0030] Figure 3 This is a block diagram of the synthetic aperture passive positioning processing system based on short baseline of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0032] Example 1: Synthetic aperture passive positioning processing method based on short baseline

[0033] Reference Figure 1 , the implementation steps of this example are as follows:

[0034] Step 1: Build a geometric scene for passive positioning.

[0035] Reference Figure 2 The geometric scene constructed in this example includes: an unknown radiation source, a reconnaissance aircraft and its two short baseline antennas.

[0036] The unknown radiation source is used to continuously transmit signals into the air. The radiation source Pi The coordinates of (X i ,R i ), X i is the radiation source P i The azimuth coordinate, R i is the radiation source P i The distance coordinate of i = 1, 2, ..., N, where N is the total number of radiation sources within the beam range;

[0037] The reconnaissance aircraft flies at a constant speed v parallel to the ground plane. The two antennas on the reconnaissance aircraft are RX1 and RX2, which are fixed at a distance d and are used to receive the unknown radiation source P. i the transmitted signal;

[0038] In the geometric scene, an XOY coordinate system is established with the first antenna RX1 of the reconnaissance aircraft as the origin. The X-axis represents the direction of the reconnaissance aircraft's flight, i.e., the azimuth, and the Y-axis represents the direction of the radiation source relative to the reconnaissance aircraft's flight path, i.e., the distance.

[0039] This example is a short baseline passive positioning geometric scenario consisting of one unknown radiation source but not limited to multiple radiation sources.

[0040] Step 2: The two short baseline antennas on the reconnaissance aircraft receive the signal from the radiation source.

[0041] 2.1) The radiation source emits a continuous wave signal s(t):

[0042] s(t)=Aexp(jφ(t))exp(j2πf c t)

[0043] Among them, A is the amplitude of the signal emitted by the radiation source, φ(t) is the phase of the signal emitted by the radiation source, and f c is the carrier frequency;

[0044] 2.2) After propagating through space, the s(t) signal reaches the reconnaissance aircraft and is received by two short baseline antennas RX1 and RX2. The received signal and They are:

[0045]

[0046] in, is the signal received by the first antenna RX1, is the signal received by the second antenna RX2, and are the amplitudes of the signals received by RX1 and RX2, φ(t-τ1) and φ(t-τ2) are the phases of the signals received by RX1 and RX2, and τ1 and τ2 are the time delays of the signals reaching RX1 and RX2, respectively.

[0047] Step 3: Process the received signal to obtain a single-frequency signal.

[0048] Since single-frequency signals have clear characteristics, the algorithm can more accurately estimate parameters such as frequency, phase, and angle of arrival during MUSIC processing, thereby improving parameter estimation accuracy. Therefore, the received signal must be processed to obtain a single-frequency signal. Its implementation includes the following:

[0049] 3.1) According to the geometric scene and the cosine theorem, the instantaneous slant distance R1 (t m ) and R2(t m )for:

[0050]

[0051] where R 10 is the instantaneous slant distance between the first antenna RX1 and the unknown radiation source P when it first receives the radiation source signal, d is the distance between the first antenna RX1 and the second antenna RX2, and t m is the time when the mth pulse is received by the two antennas RX1 and RX2, v is the speed of the reconnaissance aircraft, and θ is the angle between the straight direction of the reconnaissance aircraft and the radiation source and the flight direction of the reconnaissance aircraft, which is obtained by estimating the arrival angle DOA;

[0052] 3.2) The received signal and After down-conversion, the instantaneous slant distances R1 (t m ) and R2(t m ), and obtain the received signals of the two antennas represented by the time when the mth pulse is received and

[0053]

[0054] in, is the residual frequency offset caused by the frequency measurement error, is the measured carrier frequency,

[0055] R1(t m ) and R2(t m ) are the first antenna RX1 and the second antenna RX2 at the reconnaissance aircraft flight speed v and azimuth time t m The instantaneous slope distance under and Represent the amplitude of the signal received by the first antenna RX1 and the second antenna RX2, respectively, φ(t m -τ1) and φ(tm -τ2) are the phases of the signals received by the first antenna RX1 and the second antenna RX2 respectively;

[0056] 3.3) The instantaneous slant distance R1 (t m ) and R2(t m ) Perform Taylor series expansion and ignore higher-order terms to obtain the extended two-antenna receiving signal and for:

[0057]

[0058]

[0059] Among them, f c is the carrier frequency of the single-frequency signal, v is the speed of the reconnaissance aircraft, θ is the angle between the straight direction of the reconnaissance aircraft and the radiation source and the flight direction of the reconnaissance aircraft, d is the distance between the first antenna RX1 and the second antenna RX2, R 10 is the instantaneous slant distance between the first antenna RX1 and the unknown radiation source P when it first receives the radiation source signal;

[0060] 3.4) Received signal from the first antenna RX1 After taking the conjugate operation, the received signal of the second antenna RX2 is Multiply them together to get the single frequency signal s c (t m ):

[0061]

[0062] in, and represents the amplitude of the signal received by the first antenna RX1 and the second antenna RX2 respectively, v is the speed of the reconnaissance aircraft, θ is the angle between the straight direction of the reconnaissance aircraft and the radiation source and the flight direction of the reconnaissance aircraft, d is the distance between the first antenna RX1 and the second antenna RX2, R 10 is the instantaneous slant distance between the first antenna RX1 and the unknown radiation source P when it first receives the radiation source signal;

[0063] 3.5) Simplify the single-frequency signal and ignore the exp(j2π△f c t m ) item, and the simplified single-frequency signal s is obtained c (t m ):

[0064]

[0065] in, is a single frequency signal s c (t m ) phase, R 10 is the instantaneous slant distance between the first antenna RX1 and the unknown radiation source P when it first receives the radiation source signal, d is the distance between the first antenna RX1 and the second antenna RX2, and f c is the carrier frequency;

[0066] is a single frequency signal s c (t m ) frequency, v is the speed of the reconnaissance aircraft,

[0067] t m is the time when the mth pulse is received by the two antennas RX1 and RX2, The simplified single-frequency signal s c (t m ) amplitude.

[0068] Step 4: Process the single-frequency signal to obtain a discrete signal sequence.

[0069] Since actual signals are inevitably interfered by various noises, artificial noise addition can more realistically simulate the actual situation and improve the algorithm's adaptability to different scenarios. Discrete sample values ​​at different frequency points are obtained through sampling. These sample values ​​contain information such as the frequency and amplitude of the signal, which is the basis for signal processing by the MUSIC spectrum estimation algorithm. Its implementation is as follows:

[0070] 4.1) Noise the single-frequency signal to obtain a noisy signal

[0071]

[0072] Where w(n) is a Gaussian white noise signal, is the number of signal accumulations, △t is the sampling time interval, n is a value between 1 and N, T is the signal accumulation time, f p is the frequency of the single-frequency signal, φ p is the phase of the single-frequency signal;

[0073] 4.2) Sample the noisy signal to obtain the discrete data sequence x(n):

[0074]

[0075] Among them, δ T (n) is the sampling function.

[0076] Step 5: Perform MUSIC spectrum measurement to obtain a frequency estimation value.

[0077] 5.1) For discrete data x(n), calculate its autocorrelation matrix R:

[0078]

[0079] Where N is the data length, x(n) H is the conjugate transpose of the discrete data x(n);

[0080] 5.2) Perform eigenvalue decomposition on the autocorrelation matrix R and arrange the eigenvectors corresponding to the eigenvalues ​​to obtain the following formula:

[0081]

[0082] Among them, λ i is the i-th eigenvalue, u i is the i-th eigenvector, Λ is the eigenvalue matrix, and U is the eigenvector matrix;

[0083] 5.3) Using the eigenvector u of the decomposed autocorrelation matrix i Composing signal subspace U s and noise subspace U n , respectively expressed as follows:

[0084] U s =[u1,u2,…,u i ,…,u M ],

[0085] U n =[u M+1 ,…,u i, …,u N ],

[0086] Where M is the length of the signal subspace;

[0087] 5.4) Define the direction vector a(f) = [1,e j2πf ,e j2π2f ,…,e j2π(N-1)f ] T , consisting of the direction vector a(f) and the noise subspace U n Get MUSIC pseudo spectrum P MUSIC (f):

[0088]

[0089] 5.5) Set the spectrum interval of MUSIC pseudo spectrum to [f min ,f max ], discretize the search spectrum space with uniform sampling interval △f0 in this interval, and generate the following discrete frequency point set:

[0090]

[0091] Where k is an integer, f min is the minimum frequency, f max is the maximum frequency;

[0092] 5.6) By calculating the pseudo-spectral amplitude A of each frequency point (1) (f k ), determine the frequency corresponding to the maximum amplitude Use this frequency as the final estimated frequency

[0093]

[0094] Step 6. Estimate the value based on frequency The coupling relationship with the distance parameter is used to solve the coordinates of the radiation source.

[0095] 6.1) By best frequency estimation With the initial slope distance R 10 The coupling relationship is used to calculate the initial slant distance R required for positioning. 10 :

[0096]

[0097] Where c is the speed of light, d is the distance between the two antennas on the reconnaissance aircraft, v is the flight speed of the reconnaissance aircraft; θ is the angle between the radiation source and the flight direction of the reconnaissance aircraft, which is obtained by the arrival angle estimation DOA method, f c is the carrier frequency;

[0098] 6.2) From the initial slope distance R 10 The included angle θ between the radiation source and the flight direction of the reconnaissance aircraft is used to locate the radiation source:

[0099]

[0100] Where x0 is the horizontal position of the target and y0 is the radial position of the target.

[0101] Embodiment 2: Synthetic aperture passive positioning processing system based on short baseline.

[0102] Reference Figure 3 This example includes: a scene construction module 1, a signal receiving module 2, a correlation processing module 3 and a MUSIC spectrum frequency estimation module 4, wherein the correlation processing module 3 includes: a signal correlation operation submodule 31 and a single-frequency signal extraction submodule 32; the MUSIC spectrum estimation module 4 includes: an autocorrelation matrix calculation submodule 41, an eigenvalue decomposition submodule 42, a MUSIC spectrum calculation submodule 43 and a coordinate solution submodule 44.

[0103] The whole system works as follows:

[0104] The scenario construction module 1 is used to construct a geometric scenario including an unknown radiation source, a reconnaissance aircraft and two short baseline antennas for locating the unknown source;

[0105] The signal receiving module 2 is used to obtain the received signals on the two antennas according to the constructed geometric scene, and transmit the received signals to the relevant processing module 3;

[0106] The correlation processing module 3 is used to down-convert and perform correlation processing on the received signal to obtain a single-frequency signal, add noise to the single-frequency signal to obtain a noisy signal, and then sample the signal to obtain discrete signal data; wherein, the signal correlation operation submodule 31 is used to perform conjugate multiplication on the signals between the two antennas to obtain a signal after correlation processing, and transmit the obtained signal to the received signal single-frequency signal extraction submodule 32; the single-frequency signal extraction submodule 32 performs frequency extraction on the signal obtained by the signal correlation operation submodule to obtain a single-frequency signal coupled with the distance, and adds noise and samples the single-frequency signal in sequence to obtain discrete single-frequency signal data, and then transmits the single-frequency signal data to the MUSIC spectrum frequency estimation module 4;

[0107] The MUSIC spectrum estimation module 4 is used to perform frequency estimation on discrete signal data using a MUSIC spectrum estimation method to obtain a frequency estimation value, and solve the coordinates of the unknown radiation source based on the obtained frequency estimation value; wherein, the autocorrelation matrix calculation submodule 41 is used to calculate the autocorrelation matrix of the input signal and transmit the autocorrelation matrix to the eigenvalue decomposition submodule 42; the eigenvalue decomposition submodule 42 is used to perform eigenvalue decomposition on the autocorrelation matrix R to obtain a signal subspace and a noise subspace and transmit them to the MUSIC spectrum calculation submodule 43; the MUSIC spectrum calculation submodule 43 obtains a MUSIC pseudo-spectrum through the obtained signal subspace and noise subspace, and performs a discrete search within the spectrum interval to obtain a frequency estimation value and transmit the frequency estimation value to the coordinate solver module 44; the coordinate solver module 44 solves the coordinates of the unknown radiation source based on the obtained frequency estimation value.

[0108] It should be noted that the above-mentioned functional modules can be implemented in whole or in part through software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a program instruction product. The program instruction product includes one or a group of program instructions. When the program instructions are loaded and executed on a computer, the process or function described is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The program instructions can be stored in a computer-readable and writable storage medium, or transferred from a computer-readable storage medium to another computer-readable and writable storage medium.

[0109] The direct coupling or communication connection between the modules shown or discussed in this embodiment can be achieved through indirect coupling or communication connection of some interfaces, devices or modules. The various functional modules and submodules in this embodiment can be dynamically located in a processing component, or each module can exist physically separately, or two or more modules can be dynamically located in a processing component. The above-mentioned dynamic components can be implemented in the form of software functional modules and sold or used as independent products, or they can be stored in a computer-readable and writable storage medium. The storage medium can be a memory, a magnetic disk, an optical disk, etc.

[0110] Embodiment 3, a computer-readable storage medium for synthetic aperture spectrum.

[0111] An embodiment of the present invention provides a synthetic aperture spectrum computer-readable storage medium, which stores a plurality of instructions that can be loaded by a processor to execute the steps of any of the short-baseline synthetic aperture passive positioning methods based on MUSIC spectrum estimation provided by the embodiments of the present invention. The synthetic aperture spectrum computer-readable storage medium includes removable and non-removable media, and information storage can be implemented by any method or technology. The information can be a computer-readable instruction, a data structure, a program module, or other data. The computer storage medium includes, but is not limited to, dynamic random access memory (DRAM), read-only memory (ROM), compact disc read-only memory (CD-ROM) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices, or any other non-transmission medium for storing information that can be accessed by a computing device.

[0112] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the embodiments of the present invention and for ease of understanding, and the order of the step numbers is not limited.

Claims

1. A short baseline synthetic aperture passive positioning processing method based on MUSIC spectrum estimation, characterized in that: Use the MUSIC method to perform frequency measurements on signals with residual frequency offset removed, including: Build a geometric scene consisting of a reconnaissance aircraft, two short baseline antennas, and an unknown radiation source; According to the geometric scene, the signals of unknown radiation sources received by the two short baselines are obtained. and To receive the signal and Perform down-conversion and correlation processing to obtain a single-frequency signal s coupled with the distance parameter c (t m ), add noise to the single frequency signal to obtain a noisy signal And sample it to obtain discrete data x(n); The frequency of discrete data x(n) is estimated by MUSIC spectrum estimation method to obtain the estimated value According to the frequency estimate The coupling relationship with the distance parameter is used to solve the coordinates of the radiation source.

2. The method according to claim 1, characterized in that The setup includes a reconnaissance aircraft, two short baseline antennas, and a geometric scene with an unknown radiation source, which includes: With the initial position of the first antenna RX1 as the coordinate origin, establish an XOY coordinate system, where the X-axis represents the coordinate axis parallel to the reconnaissance aircraft's straight flight direction, and the Y-axis represents the coordinate axis perpendicular to the reconnaissance aircraft's flight direction; The two antennas on the reconnaissance aircraft are RX1 and RX2, with a fixed interval of d between them. The reconnaissance aircraft flies at a constant speed v parallel to the ground plane and receives the unknown radiation source P during the flight. i The transmitted signal.

3. The method according to claim 1, characterized in that The signal of the radiation source received by the two short baseline antennas on the reconnaissance aircraft is obtained according to the geometric scene and They are respectively represented as follows: in, and are the amplitudes of the signals received by RX1 and RX2, φ(t-τ1) and φ(t-τ2) are the phases of the signals received by RX1 and RX2, τ1 and τ2 are the time delays of the unknown radiation source signal reaching RX1 and RX2, respectively. c is the carrier frequency.

4. The method according to claim 1, wherein The pair receives the signal and Perform down-conversion and correlation processing to obtain a single-frequency signal s coupled with the distance parameter c (t m ), whose implementation includes: 4a) According to the geometric scene and the law of cosines, the instantaneous slant distance R1 (t m ) and R2(t m )for: Where d is the distance between the two antennas on the reconnaissance aircraft, v is the flight speed of the reconnaissance aircraft, R 10 is the instantaneous slant range from P when RX1 first receives the radiation source signal, and θ is the angle between the radiation source and the flight direction of the reconnaissance aircraft at this time, which is obtained by estimating the angle of arrival (DOA); 4b) The received signal and After down-conversion, the distance R1 (t m ) and R2(t m ), get the received signal represented by the time of the mth pulse and in, and are the received signal amplitudes of RX1 and RX2 respectively, is the residual frequency offset caused by the frequency measurement error, is the measured carrier frequency, R1(t m ) and R2(t m ) are RX1 and RX2 at the reconnaissance aircraft flight speed v and the mth pulse time t m The instantaneous slant range under , τ1 and τ2 are the time delays of the unknown radiation source signal reaching RX1 and RX2 respectively, and c is the speed of light; 4c) Perform Taylor series expansion on the instantaneous slant range expression, ignore its higher-order terms, and then take the conjugate operation on the received signal of RX1 and multiply it with the received signal of RX2 to obtain the single-frequency signal s c (t m ): Where d is the distance between the two antennas on the reconnaissance aircraft, v is the flight speed of the reconnaissance aircraft, R 10 is the instantaneous slant distance from P when the first antenna RX1 receives the radiation source signal for the first time, θ is the angle between the radiation source and the flight direction of the reconnaissance aircraft at this time, which is obtained by estimating the angle of arrival (DOA), and c is the speed of light; Simplify the above formula to get the simplified single-frequency signal s c (t m ): in, is a single frequency signal s c (t m ) frequency, v is the speed of the reconnaissance aircraft, t m is the time when the mth pulse is received by the two antennas RX1 and RX2, The simplified single-frequency signal s c (t m ) is a single frequency signal s c (t m ) phase, R 10 is the instantaneous slant distance between the first antenna RX1 and the unknown radiation source P when it first receives the radiation source signal, d is the distance between the first antenna RX1 and the second antenna RX2, and f c is the carrier frequency.

5. The method according to claim 1, wherein The single-frequency signal is subjected to noise addition processing to obtain a noise-added signal And sample it to get discrete data x(n), which are expressed as follows: Where w(n) is a Gaussian white noise signal, is the number of signal accumulations, △t is the sampling time interval, n is a value between 1 and N, T is the signal accumulation time, f p is the frequency of the single-frequency signal, φ p is the phase of the single-frequency signal, δ T (n) is the sampling function.

6. The method according to claim 1, characterized in that The MUSIC spectrum estimation method is used to estimate the frequency of the discrete data x(n) to obtain the estimated value Its implementation includes: 6a) For discrete data x(n), calculate its autocorrelation matrix R: Where N is the data length, x(n) H is the conjugate transpose of the discrete data x(n); 6b) Perform eigenvalue decomposition on the autocorrelation matrix R and arrange the eigenvectors corresponding to the eigenvalues ​​to obtain the following formula: Among them, λ i is the i-th eigenvalue, u i is the i-th eigenvector, Λ is the eigenvalue matrix, and U is the eigenvector matrix; 6c) Using the eigenvector u of the decomposed autocorrelation matrix i Composing signal subspace U s and noise subspace U n , respectively expressed as follows: U s =[u1,u2,…,u i ,…,u M ], IN n =[in M+1 ,…,in i, …,in N ]; 6d) Define the direction vector a(f) = [1,e j2πf ,e j2π2f ,…,e j2π(N-1)f ] T , consisting of the direction vector a(f) and the noise subspace U n Get MUSIC pseudo spectrum P MUSIC (f): 6e) Set the spectrum interval of MUSIC pseudo spectrum to [f min ,f max ], discretize the search spectrum space with uniform sampling interval △f0 in this interval, and generate the following discrete frequency point set: Where k is an integer, f min is the minimum frequency, f max is the maximum frequency; 6f) Calculate the pseudo-spectrum amplitude A of each frequency point (1) (f k ), the frequency corresponding to the maximum amplitude The final estimated frequency 7. The method according to claim 1, characterized in that The frequency estimate The coupling relationship with the distance parameter is used to solve the radiation source coordinates, which includes: 7a) By best frequency estimate With the initial slope distance R 10 The coupling relationship is used to calculate the initial slant distance R required for positioning. 10 : Where c is the speed of light, d is the distance between the two antennas on the reconnaissance aircraft, v is the flight speed of the reconnaissance aircraft; θ is the angle between the radiation source and the flight direction of the reconnaissance aircraft, which is obtained by the arrival angle estimation DOA method, f c is the carrier frequency; 7b) From the initial slope distance R 10 The included angle θ between the radiation source and the flight direction of the reconnaissance aircraft is used to locate the radiation source: Where x0 is the horizontal position of the target and y0 is the radial position of the target.

8. A synthetic aperture passive positioning processing system based on short baseline, characterized in that: include: The scenario construction module is used to build a geometric scenario including an unknown radiation source, a reconnaissance aircraft and its two short baseline antennas to locate the unknown source; Signal receiving module: used to receive unknown radiation source signals through the dual short baseline model; Correlation processing module: used to perform down-conversion and correlation processing on the received signal to obtain a single-frequency signal coupled with the distance parameter, add noise to the single-frequency signal to obtain a noisy signal, and then sample the signal to obtain discrete signal data; MUSIC spectrum estimation module: used to perform frequency estimation on discrete signal data using the MUSIC spectrum estimation method, obtain frequency estimation values, and calculate the coordinates of unknown radiation sources based on the obtained frequency estimation values.

9. The system according to claim 8, characterized in that: The relevant processing modules include: The signal correlation operation submodule is used to perform conjugate multiplication on the signals between the two antennas to obtain the correlated signal; The single-frequency signal extraction submodule is used to extract the frequency of the signal obtained by the signal correlation operation submodule to obtain a single-frequency signal coupled with the distance, and to add noise and sample the single-frequency signal in sequence to obtain discrete single-frequency signal data; The MUSIC spectrum estimation module includes: An autocorrelation matrix calculation submodule is used to calculate the autocorrelation matrix of the input signal; The eigenvalue decomposition submodule is used to perform eigenvalue decomposition on the autocorrelation matrix R to obtain the signal subspace and the noise subspace; The MUSIC spectrum calculation submodule is used to obtain the MUSIC pseudo-spectrum based on the obtained signal subspace and noise subspace, and perform a discretization search within the spectrum interval to obtain the frequency estimation value; The coordinate solver module is used to solve the coordinates of the unknown radiation source based on the obtained frequency estimation value.

10. A computer-readable storage medium for synthetic aperture spectrum, characterized in that: The synthetic aperture spectrum computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the short-baseline synthetic aperture passive positioning method based on MUSIC spectrum estimation according to any one of claims 1 to 7.

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