Short-baseline synthetic aperture passive positioning method and system based on Chirp-Z spectrum estimation

Abstract

The invention discloses a short baseline synthetic aperture passive positioning method and system based on Chirp-Z 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 sequence; a Chirp-Z spectrum estimation algorithm is adopted for the single-frequency signal sequence to obtain a frequency estimation value, and the coordinates of the radiation source are calculated according to the frequency estimation value. According to the invention, frequency measurement is carried out by using a Chirp-Z spectrum estimation method, and Z transformation is converted into an FFT processable form through convolution operation, so that the operation complexity and spectrum estimation errors are reduced, phase ambiguity and signal coherence dependence are avoided, the reliability of the model is improved, and the method is suitable for large-scale popularization and application. The method can be used for an unknown signal source which has a short baseline and does not have a periodic discontinuous short signal sequence.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and further relates to a synthetic aperture passive positioning method, which can be used for unknown signal sources with short baselines and non-periodic discontinuous short signal sequences. 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] Dr. Wang Yuqi's paper, "Research on Imaging and Localization Methods of Radiating Sources Based on Synthetic Aperture Systems" (Xi'an University of Electronic Science and Technology, 2023), proposes a satellite-based, long-duration synthetic aperture positioning method to minimize the impact of carrier frequency estimation errors on positioning accuracy. Its implementation involves: first, establishing a high-order slant range model from the receiving platform to the radiating source. By decomposing the line frequency modulation, an azimuth-matched filter is constructed. A azimuth-focusing-based minimum entropy method is used to estimate the high-order frequency modulation of the received signal. Then, a cost function is constructed to locate the radiating source using a grid structure in the geographic coordinate system. Finally, a positioning performance analysis method based on the orthogonality of the high-order terms is proposed to clarify the algorithm's ability to locate signal sources at different locations. However, this method requires a large amount of computation, which affects the real-time performance of radiating source positioning. Furthermore, the processing of range and residual frequency offsets is complex, resulting in low frequency estimation accuracy.

[0004] Patent document CN202411496349.9 discloses a "Radar Phase Difference UAV Altitude Measurement Method Based on Spectral Refinement Calibration." The method first receives radar echo carrier signals and mixes the intermediate frequency signals to form a radar data cube. The data cube's distance dimension is converted to the time-frequency domain to obtain a one-dimensional radar range sequence. Interference clutter is filtered out using constant false alarm detection technology, and the maximum peak value within the range is searched to determine the range threshold of the observation area. Spectral refinement is performed on specific frequency bands in the observation area using Chirp-Z transform. A quadratic polynomial is constructed using parabolic fitting for spectrum line calibration, obtaining frequency information of the observation area after spectrum refinement and calibration. The phase sequence of the observation area's range threshold is extracted, and phase unwrapping is used to unwrap the phases of adjacent frames. Combining frequency and phase information, the method determines the drone's relative ground height. While this method can help drones quickly provide feedback on their relative ground height and avoid collision risks, the complex data processing algorithm and the lengthy processing time result in a lack of timely data processing efficiency. 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 short-baseline synthetic aperture passive positioning method and system based on Chirp-Z spectrum estimation to improve the estimation accuracy of signal frequency, achieve high-precision spectrum estimation and real-time positioning of the radiation source.

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

[0007] 1. A short-baseline synthetic aperture passive location processing method based on Chirp-Z spectrum estimation, characterized in that the Chirp-Z method is used to perform frequency measurement on a signal from which residual frequency offset has been eliminated, comprising:

[0008] (1) Build a geometric scene consisting of a reconnaissance aircraft, two short baseline antennas, and an unknown radiation source;

[0009] (2) Obtain the signal of the radiation source received by the two short baseline antennas on the reconnaissance aircraft based on the geometric scene and

[0010] (3) Received signal and Perform down-conversion and correlation processing to obtain a single-frequency signal sequence

[0011] (4) For single-frequency signal sequence Perform Chirp-Z spectrum estimation to obtain frequency estimates

[0012] (5) Based on frequency estimation Solve for the radiation source coordinates.

[0013] Furthermore, the single frequency signal sequence in (4) Perform Chirp-Z spectrum estimation to obtain frequency estimates Its implementation includes:

[0014] 4a) According to the obtained single frequency signal sequence The single frequency signal sequence is converted into Convert to a frequency domain analyzable form w(n):

[0015] 4b) Define the weight function w'(n,k):

[0016] 4c) Convert the weight function w'(n,k) into the frequency domain form W' k (w):

[0017] 4d) Align the spectrum of the FM signal with the spectrum of the weight function through frequency domain multiplication, so that the result after IFFT only retains the target frequency point z k The corresponding frequency component X(z k ):

[0018] 4e) Set the spectrum interval and find the frequency corresponding to the frequency point m with the maximum frequency amplitude in the spectrum interval. This is the frequency estimate.

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

[0020] The scene construction module is used to build a geometric scene for locating unknown radiation sources;

[0021] A signal receiving module is used to obtain the received signals on the two antennas according to the geometric scene;

[0022] A signal processing module is used to perform down-conversion and correlation processing on the signal received in the geometric scene to obtain a single-frequency signal sequence;

[0023] The Chirp-Z spectrum estimation module is used to perform Chirp-Z spectrum estimation on the obtained single-frequency signal sequence to obtain a frequency estimation value, and then obtain the coordinates of the unknown radiation source.

[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 Chirp-Z spectrum estimation.

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

[0026] First, the present invention performs correlation processing on the received signals obtained by the two antennas to obtain a single-frequency signal sequence, which can transform the original positioning problem into a frequency estimation problem of the signal to be measured, reducing the implementation cost and achieving high-precision positioning of unknown radiation sources.

[0027] Second, when performing synthetic aperture passive positioning, the present invention uses a reconnaissance aircraft equipped with dual short baseline antennas to locate the unknown radiation source signal and uses Chirp-Z spectrum estimation to perform frequency measurement. While avoiding phase ambiguity and signal coherence dependence, it also reduces the impact of residual frequency offset caused by inaccurate estimation of the carrier frequency of the radiation source emission signal, thereby reducing computational complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the implementation of the synthetic aperture passive positioning processing method based on short baseline 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 P i The coordinates of (X i ,R i ), X iis 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 signal transmitted;

[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] The continuous wave signal s(t) emitted by the radiation source is:

[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] The s(t) signal propagates through space and reaches the reconnaissance aircraft, where it is received by two short baseline antennas RX1 and RX2. 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 sequence.

[0048] Since the single-frequency signal sequence has clear characteristics, the Chirp-Z processing algorithm can more accurately estimate its frequency, phase, arrival angle and other parameters, thereby improving the parameter estimation accuracy. Therefore, the received signal must be processed to obtain the single-frequency signal sequence. 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(t m -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 10is 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 )

[0068] 3.6) Transform the single frequency signal s c (t m ) passes through the Gaussian white noise channel to obtain a single-frequency signal sequence for:

[0069]

[0070] Where w(n) is a Gaussian white noise signal, is the number of signal accumulations, T is the signal accumulation time, △t m is the sampling interval.

[0071] Step 4: For the single frequency signal sequence Perform Chirp-Z spectrum estimation to obtain frequency estimates

[0072] 4.1) According to the obtained single frequency signal sequence The single frequency signal sequence is converted into Convert to a frequency domain analyzable form w(n):

[0073]

[0074] Where π / N is the slope;

[0075] 4.2) Define the weight function w'(n,k):

[0076]

[0077] in is the normalized frequency, N is the number of sampling points;

[0078] 4.3) The weight function w'(n,k) is used to focus the modulated signal to the target frequency point z k , in order to obtain the target frequency point zk Corresponding frequency components, the weight function w'(n,k) needs to be converted into the frequency domain form W' k (w):

[0079]

[0080] 4.4) Through the frequency domain product Y k =W⊙W' k , align the spectrum of the FM signal with the spectrum of the weight function so that the result after IFFT only retains the target frequency point z k The corresponding frequency component X(z k ):

[0081]

[0082] 4.5) Set the spectrum interval to f L <f<f R , where f L is the minimum frequency, f R For the maximum frequency, find the frequency point corresponding to the maximum frequency amplitude in the spectrum interval The frequency corresponding to the frequency point m is the frequency estimate

[0083]

[0084] Step 5: Calculate the coordinates of the unknown radiation source.

[0085] 5.1) According to the estimated frequency value Solve the initial slant distance R required for positioning 10 :

[0086]

[0087] Where c is the speed of light, d is the distance between the first antenna RX1 and the second antenna RX2, v is the speed of the reconnaissance aircraft, θ is the angle between the straight direction of the reconnaissance aircraft and the unknown radiation source and the flight direction of the reconnaissance aircraft, and f is the distance between the first antenna RX1 and the second antenna RX2, v is the speed of the reconnaissance aircraft, θ is the angle between the straight direction of the reconnaissance aircraft and c is the carrier frequency;

[0088] 5.2) From the initial slope distance R 10 The unknown radiation source is located by estimating the DOA with the known angle of arrival, and the coordinates of the unknown radiation source are:

[0089]

[0090] Embodiment 2: Synthetic aperture passive positioning processing system based on short baseline.

[0091] Reference Figure 3This example includes: a scene construction module 1, a signal receiving module 2, a signal processing module 3 and a Chirp-Z spectrum estimation module 4. Among them, the signal processing module 3 includes: an instantaneous slant range submodule 31, a received signal down-conversion submodule 32, and a single-frequency signal submodule 33. The Chirp-Z spectrum estimation module 4 includes: a weight function submodule 41, a frequency domain product submodule 42, and a coordinate solution submodule 43. Its working principle is as follows:

[0092] 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;

[0093] 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 signal processing module 3;

[0094] The signal processing module 3 is used to down-convert and perform correlation processing on the received signal to obtain a single-frequency signal; wherein the instantaneous slant distance submodule 31 calculates the instantaneous slant distances between the first antenna and the second antenna and the radiation source respectively, and transmits the obtained instantaneous slant distances to the received signal down-conversion submodule 32; the received signal down-conversion submodule 32 obtains the received signals on the two antennas through the calculated instantaneous slant distances and performs down-conversion and correlation processing to obtain a single-frequency signal, and then transmits the single-frequency signal to the single-frequency signal submodule 33; the single-frequency signal submodule 33 performs relevant simplification operations on the obtained single-frequency signal to obtain a single-frequency signal sequence that is convenient for using Chirp-Z spectrum estimation, and transmits the single-frequency signal sequence to the Chirp-Z spectrum estimation module 4;

[0095] The Chirp-Z spectrum estimation module 4 is used to perform Chirp-Z spectrum estimation on the obtained single-frequency signal sequence to obtain a frequency estimation value, and then obtain the coordinates of the unknown radiation source; wherein, the weight function submodule 41 modulates the single-frequency signal sequence, and then focuses the modulated signal to the target frequency point through the weight function, and transmits the target frequency point to the frequency domain product submodule 42; the frequency domain product submodule 42 calculates the frequency component at the target frequency point, and then calculates the frequency point corresponding to the maximum frequency amplitude in the spectrum component, and then obtains the frequency estimation value, and transmits the frequency estimation value to the coordinate solver module 43; the coordinate solver module 43 calculates the coordinates of the unknown radiation source based on the obtained frequency estimation value.

[0096] 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.

[0097] 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.

[0098] Embodiment 3, a computer-readable storage medium for synthetic aperture spectrum.

[0099] 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 Chirp-Z 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.

[0100] 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 Chirp-Z spectrum estimation, characterized in that: include: (1) Build a geometric scene consisting of a reconnaissance aircraft, two short baseline antennas, and an unknown radiation source; (2) Obtain the signal of the radiation source received by the two short baseline antennas on the reconnaissance aircraft based on the geometric scene and (3) Received signal and Perform down-conversion and correlation processing to obtain a single-frequency signal sequence (4) Using Chirp-Z method to analyze the single frequency signal sequence Perform frequency measurements and obtain frequency estimates (5) Based on frequency estimation Solve for the radiation source coordinates.

2. The method according to claim 1, characterized in that The (1) construction includes a geometric scene including a reconnaissance aircraft, two short baseline antennas and an unknown radiation source, which includes: Establish an XOY coordinate system, where 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. Assume that the two antennas on the reconnaissance aircraft are RX1 and RX2, with a fixed interval d between them. The initial position of the first antenna RX1 is taken as the coordinate origin. The reconnaissance aircraft flies at a uniform speed v parallel to the ground plane. During the flight, it receives the unknown radiation source P. i the transmitted signal; Assume that the unknown radiation source P i The coordinates of (X i ,R i ), where X i is the radiation source P i The azimuth coordinate, R i is the radiation source P i The distance coordinates of , i = 1, 2, ..., N, where N is the total number of radiation sources within the beam range.

3. The method according to claim 1, characterized in that In (2), the signal of the radiation source received by the first antenna RX1 and the second antenna RX2 on the reconnaissance aircraft is obtained according to the geometric scene. and The expressions are 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 signals arriving at RX1 and RX2, respectively. c is the carrier frequency.

4. The method according to claim 1, wherein The received signal in (3) and Perform down-conversion and correlation processing to obtain a single-frequency signal sequence It includes: 3a) According to the geometric scene and the cosine theorem, the instantaneous slant distance R1 (t m ) and R2(t m )for: 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; 3b) The received signal and After down-conversion, the instantaneous slant distances R1 (t m ) and R2(t m ), and obtain the received signal represented by the time when the mth pulse is received and for: in, is the residual frequency offset caused by the frequency measurement error, is the measured carrier frequency, R1(t m ) and R2(t m ) are respectively the flight speed v and azimuth time t of RX1 and RX2 in the reconnaissance aircraft m The instantaneous slope distance under and Represent the amplitudes of the signals received by the first antenna RX1 and the second antenna RX2 respectively; 3c) According to the received signal and Calculate the single frequency signal s c (t m )for: 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, θ is the angle between the straight direction of the reconnaissance aircraft and the radiation source and the flight direction of the reconnaissance aircraft, 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 ) 3d) The obtained single frequency signal s c (t m ) passes through the Gaussian white noise channel to obtain a single-frequency signal sequence for: Where w(n) is a Gaussian white noise signal, is the number of signal accumulations, T is the signal accumulation time, △t m is the sampling interval.

5. The method according to claim 4, characterized in that In (3c), according to the received signal and Calculate the single frequency signal s c (t m ), whose implementation includes: 3c1) Received signal of the first antenna RX1 After the conjugate operation, it is combined with the received signal of the second antenna RX2 Multiplication, the formula is as follows: 3c2) Substitute the instantaneous slant distances R1 (t1) between the first antenna RX1 and the second antenna RX2 and the radiation source in formula 3c1) m ) and R2(t m ) to perform Taylor series expansion, ignoring its higher-order terms and ignoring exp(j2π△f c (t m )) item, calculate the simplified single-frequency signal s c (t m ): Here, "*" represents the conjugate operation.

6. The method according to claim 1, characterized in that The single frequency signal sequence described in step (4) Perform Chirp-Z spectrum estimation to obtain frequency estimates include: 4a) According to the obtained single frequency signal sequence The single frequency signal sequence is converted into Convert to a frequency domain analyzable form w(n): Where π / N is the slope; 4b) Define the weight function w'(n,k): in is the normalized frequency, N is the number of sampling points, and the weight function w'(n,k) is used to focus the FM signal to the target frequency point z k ; 4c) Convert the weight function w'(n,k) into the frequency domain form W' k (w): 4d) Through the frequency domain product Y k =W⊙W' k , align the spectrum of the FM signal with the spectrum of the weight function so that the result after IFFT only retains the target frequency point z k The corresponding frequency component X(z k ): Where N is the number of sampling points; 4e) Set the spectrum interval to f L <f<f R , where f L is the minimum frequency, f R For the maximum frequency, find the frequency point corresponding to the maximum frequency amplitude in the spectrum interval The frequency corresponding to the frequency point m is the frequency estimate 7. The method according to claim 1, characterized in that The step (5) is based on the frequency estimation value Solve the coordinates of unknown radiation sources, which includes: 5a) Based on the estimated frequency value Solve the initial slant distance R required for positioning 10 : Where c is the speed of light, d is the distance between the first antenna RX1 and the second antenna RX2, v is the speed of the reconnaissance aircraft, θ is the angle between the straight direction of the reconnaissance aircraft and the unknown radiation source and the flight direction of the reconnaissance aircraft, and f ... angle between the first antenna RX1 and the second antenna RX2, and f is the angle between the first antenna RX1 and the second antenna RX2, and f is the angle between the first antenna RX1 and the second antenna RX2, and f is the angle between the first antenna RX1 and the second antenna RX2, and f is the angle between the first antenna RX1 and the second antenna RX2, and f is the angle between the first antenna RX c is the carrier frequency; 5b) From the initial slope distance R 10 The unknown radiation source is located by estimating the angle of arrival (DOA) using θ:

8. A synthetic aperture passive positioning processing system based on short baseline, characterized in that: include: The scene construction module is used to build a geometric scene for locating unknown radiation sources; A signal receiving module is used to obtain the received signals on the two antennas according to the geometric scene; A signal processing module is used to perform down-conversion and correlation processing on the signal received in the geometric scene to obtain a single-frequency signal; The Chirp-Z spectrum estimation module is used to perform Chirp-Z spectrum estimation on the obtained single-frequency signal sequence to obtain a frequency estimation value, and then obtain the coordinates of the unknown radiation source.

9. The system according to claim 8, characterized in that: The signal processing module includes: The instantaneous slant distance submodule is used to obtain the instantaneous slant distances between the first antenna and the second antenna and the radiation source respectively; The receiving signal down-conversion submodule is used to obtain the received signals on the two antennas according to the obtained instantaneous slant range and perform down-conversion and correlation processing on them to obtain a single-frequency signal; The single-frequency signal submodule is used to perform related simplification operations on the obtained single-frequency signal to obtain a single-frequency signal sequence. The Chirp-Z spectrum estimation module includes: The weight function submodule is used to modulate the single-frequency signal sequence and then focus the modulated signal to the target frequency point through the weight function; The frequency domain product submodule is used to calculate the frequency component at the target frequency point, and then find the frequency point corresponding to the maximum frequency amplitude in the spectrum component, and then 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 Chirp-Z spectrum estimation according to any one of claims 1 to 7.

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