CN115453477B - Method for canceling multipath clutter in external radiation source radar monitoring channel signal - Google Patents

Abstract

The present invention discloses a method for canceling multipath clutter in a monitoring channel signal of an external radiation source radar, comprising: using a reference channel and a monitoring channel of the external radiation source radar to obtain a reference signal and a monitoring signal respectively; performing down-conversion processing on the reference signal and the monitoring signal to obtain a baseband reference signal and a baseband monitoring signal after down-conversion; using the baseband reference signal and the baseband monitoring signal to estimate the number of multipath clutter signals in the monitoring channel; according to the estimated number of multipath clutter signals, using an orthogonal matching pursuit method to perform sparse matching cancellation on the multipath clutter signal to obtain a multipath clutter sparse coefficient; using the multipath clutter sparse coefficient to perform sparse matching cancellation on the multipath clutter to obtain a signal after multipath clutter cancellation. The dimension of the clutter filter matrix of the present invention is only related to the number of multipath clutter contained in the monitoring channel signal, so the complexity of solving the sparse matching coefficient can be greatly reduced, and the calculation efficiency can be improved.

Description

A method for canceling multipath clutter in external radiation source radar monitoring channel signal

Technical Field

The present invention belongs to the technical field of radar signal processing, and in particular relates to a method for canceling multipath clutter in a monitoring channel signal of an external radiation source radar, which is used for accurately canceling multipath clutter in a monitoring channel of an external radiation source radar system.

Background Art

Exo-radiation radar is a new type of radar that uses third-party electromagnetic signals (such as digital broadcasting and television signals, communication or navigation satellite signals, global mobile communication systems, etc.) to detect targets. Exo-radiation radar is usually equipped with a reference antenna for receiving radiation source signals and a monitoring antenna for receiving target echo signals. The signals received by the reference antenna and the monitoring antenna are called reference signals and monitoring signals, respectively. Ideally, the reference signal is a pure radiation source signal, and the monitoring signal only contains the radiation source signal after secondary reflection by the target (i.e., the target echo signal). The reference signal and the monitoring signal are coherently accumulated to obtain the time delay and Doppler frequency of the echo signal relative to the reference signal. Based on this, many applications such as target detection, positioning, and tracking can be realized. However, the monitoring signal actually received contains some strong multipath clutter and direct waves. These signals will generate a large number of false targets when coherently accumulated, which brings difficulties to the target detection of exo-radiation radar.

At present, the most widely used multipath clutter cancellation methods include time domain adaptive filtering methods, such as Least Mean Squares (LMS), Normalized Least Mean Squares (NLMS), Gradient Adaptive Lattice (GAL), Recursive Least Squares (RLS), etc.; and time domain projection methods, such as Extensive Cancellation Algorithm (ECA), ECA-B (ECA-Batch), ECA-S (ECA-Sliding), ECA-C (ECA-Carrie), etc. Among them, the adaptive filtering method has a slow convergence speed and the parameter value depends on historical experience; the time domain projection method does not have a convergence problem, but the amount of calculation for matrix inversion is large and the solution speed is slow.

Summary of the invention

In order to solve the above problems existing in the prior art, the present invention provides a method for canceling multipath clutter in the monitoring channel signal of an external radiation source radar. The technical problem to be solved by the present invention is achieved by the following technical solutions:

One aspect of the present invention provides a method for canceling multipath clutter in an external radiation source radar monitoring channel signal, comprising:

S1: using a reference channel and a monitoring channel of an external radiation source radar to obtain a reference signal and a monitoring signal respectively, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target;

S2: down-converting the reference signal and the monitoring signal to obtain a baseband reference signal and a baseband monitoring signal after down-conversion;

S3: using the baseband reference signal and the baseband monitoring signal to estimate the number of multipath clutter signals in the monitoring channel;

S4: according to the estimated number of multipath clutter signals, sparse matching cancellation is performed on the multipath clutter signals using an orthogonal matching pursuit method to obtain a multipath clutter sparse coefficient;

S5: performing sparse matching cancellation on the multipath clutter using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation.

In one embodiment of the present invention, the S1 includes:

S1a: Set the sampling frequency _fs and beam receiving direction of the external radiation source radar receiver Receiving bandwidth B and detection threshold _Th ;

S1b: Setting the minimum value d _min and the maximum value d _max of the delay unit for the occurrence of multipath clutter signals according to the dual-base detection range of different scenarios;

S1c: using the reference channel of the external radiation source radar to receive a reference signal, and using the monitoring channel of the external radiation source radar to receive a monitoring signal.

In one embodiment of the present invention, the S2 includes:

The received reference signal and monitoring signal are digitally down-converted to obtain a down-converted baseband reference signal s _ref (t) and a baseband monitoring signal s _surv (t):

s _surv (t)＝s _echo (t)+s _m (t)+w(t)

Wherein, _f0 is the center frequency of the baseband signal, s _echo (t) represents the target echo signal received by the monitoring channel, s _m (t) represents the multipath clutter signal received by the monitoring channel, w(t) is Gaussian white noise, and the target echo signal s _echo (t) is expressed as:

Where A is the complex amplitude of the target echo signal, u(t) is the complex envelope of the reference signal, τ is the time delay of the target echo signal relative to the reference signal, and _fd is the Doppler frequency of the target echo signal.

In one embodiment of the present invention, S3 includes:

S3a: Calculate the cross-correlation function between the baseband reference signal and the baseband monitoring signal:

χ ₀ (n)=IFFT{FFT[s _ref (n),2N]·FFT ^* [s _surv (n),2N]}

Wherein, n is a discrete time point, s _ref (n) is a discretized representation of a baseband reference signal s _ref (t), s _surv (n) is a discretized representation of a baseband monitoring signal s _surv (t), N is the length of the baseband reference signal and the baseband monitoring signal, FFT(·) represents Fourier transform, and IFFT(·) represents inverse Fourier transform;

S3b: Record the average value of the part of the correlation result of the cross-correlation function χ ₀ (n) in the time delay unit [d _min , d _max ] that exceeds the detection threshold _Th :

A _ve =mean(χ ₀ (n)>T _h );

S3c: The part of the correlation results of χ ₀ (n) in the delay unit [d _min ,d _max ] that exceeds γ·A _ve is formed into a new array χ ₁ , where γ is a constant factor;

S3d: Count the number of maximum values cnt in the new array χ ₁ , and estimate the number of multipath clutter signals to be M ₀ =η·cnt, where η is a constant factor.

In one embodiment of the present invention, the S4 includes:

S4a: Generate a multipath clutter word space matrix D according to the discretized baseband reference signal s _ref (n):

Wherein, K = d _max -d _min , n represents discrete time, N represents signal length, f _s represents the sampling frequency of the external radiation source radar receiver, and there are d _min zeros before s _ref (1) in the first column of the matrix D, and there are K + d _min + 1 zeros before s _ref (1) in the last column;

S4b: Unitize each column of the multipath clutter word space matrix D:

D＝[a ₁ ,a ₂ ,…,a _K ]，

Wherein, a _i represents the normalized multipath clutter signal, i=1,...,K;

S4c: Initialize the residual signal after cancellation r ₀ =s _surv , and initialize the multipath clutter matrix index set Λ and the number of iterations m: m=1;

S4d: Calculate the position index λ _m of the current multipath clutter signal in the multipath clutter word space matrix D:

Where m represents the number of iterations;

S4e: Add the obtained position index λ _m to the multipath clutter matrix index set

Λ _m = Λ _m-1 ∪{λ _m };

S4f: Update the residual signal using the multipath clutter matrix index set:

in, is part of the multipath clutter word space matrix D, is a new spatial matrix composed of column signals corresponding to the index set Λ _m ;

S4g: Let m = m + 1, repeat steps S4d-S4g, and exit the loop when the iteration exit condition m = M ₀ is met to obtain the multipath clutter word space matrix after iterative update Where _M0 is the number of estimated multipath clutter signals.

S4h: Using the iteratively updated multipath clutter word space matrix Calculate the multipath clutter sparse coefficient:

Wherein, s _surv represents the baseband monitoring signal.

In one embodiment of the present invention, the S5 includes:

The multipath clutter sparse coefficient is used to perform sparse matching cancellation on the multipath clutter to obtain a signal after multipath clutter cancellation:

Another aspect of the present invention provides a storage medium storing a computer program for executing the steps of the method for cancelling multipath clutter in an external radiation source radar monitoring channel signal described in any one of the above embodiments.

Another aspect of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor calls the computer program in the memory, it implements the steps of the method for eliminating multipath clutter in the external radiation source radar monitoring channel signal as described in any one of the above embodiments.

Compared with the prior art, the present invention has the following beneficial effects:

1. In the orthogonal matching pursuit multipath clutter cancellation method adopted by the present invention, the dimension of the clutter filter matrix is only related to the number of multipath clutter contained in the monitoring channel signal, so the complexity of solving the sparse matching coefficient can be greatly reduced and the calculation efficiency can be improved.

2. The orthogonal matching pursuit multipath clutter cancellation method adopted in the present invention has no special requirements on the correlation of the column vectors of the multipath clutter filter matrix, and is therefore suitable for more practical application scenarios.

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

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a flow chart of a method for canceling multipath clutter in an external radiation source radar monitoring channel signal provided by an embodiment of the present invention;

2 is a schematic diagram of a processing process of a method for canceling multipath clutter in an external radiation source radar monitoring channel signal provided by an embodiment of the present invention;

FIG3 is a slice diagram of a zero-frequency mutual ambiguity function before clutter cancellation using the cancellation method according to an embodiment of the present invention;

FIG4 is a schematic diagram showing that the cross-correlation result in the delay unit exceeds the detection threshold;

FIG. 5 is a cross-ambiguity function slice diagram after clutter cancellation using the cancellation method according to an embodiment of the present invention.

DETAILED DESCRIPTION

In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the method for canceling multipath clutter in the external radiation source radar monitoring channel signal proposed by the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the statement "including one..." do not exclude the existence of other identical elements in the article or device including the elements.

The embodiment of the present invention provides a method for canceling multipath clutter in an external radiation source radar monitoring channel signal. Please refer to Figures 1 and 2. The method for canceling multipath clutter includes the following steps:

S1: Use the reference channel and monitoring channel of the external radiation source radar to obtain a reference signal and a monitoring signal respectively.

Specifically, step S1 of this embodiment includes the following sub-steps:

S1a: Set the sampling frequency _fs and beam receiving direction of the external radiation source radar receiver Parameters such as receiving bandwidth B and detection threshold _Th .

S1b: Set the relevant parameters of multipath clutter signals. Set the minimum value d _min and the maximum value d _max of the delay unit where multipath clutter signals appear according to the dual-base detection range [R _min , R _max ] of different scenarios, that is,

Where c is the speed of light and floor(·) means rounding down.

S1c: using the reference channel of the external radiation source radar to receive a reference signal, and using the monitoring channel of the external radiation source radar to receive a monitoring signal, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target.

As mentioned above, external radiation source radar is usually equipped with a reference antenna for receiving radiation source signals and a monitoring antenna for receiving target echo signals. The signals received by the reference antenna and the monitoring antenna are called reference signal and monitoring signal respectively. Ideally, the reference signal is a pure radiation source signal, and the monitoring signal only contains the radiation source signal after secondary reflection from the target (i.e., the target echo signal). In actual situations, the received reference signal can be expressed as:

Where u(t) is the complex envelope of the reference signal, _fc is the carrier frequency of the transmitted signal, is the initial phase of the transmitted signal, and t represents time.

S2: Perform down-conversion processing on the reference signal and the monitoring signal to obtain a down-converted baseband reference signal and a baseband monitoring signal.

Specifically, the received high-frequency reference signal and monitoring signal are digitally down-converted to obtain a down-converted baseband reference signal s _ref (t) and a baseband monitoring signal s _surv (t), which are respectively expressed as

s _surv (t)＝s _echo (t)+s _m (t)+w(t)

Where _f0 is the center frequency of the baseband signal, s _echo (t) represents the target echo signal received by the monitoring channel, s _m (t) represents the multipath clutter signal received by the monitoring channel, and w(t) is Gaussian white noise. The target echo signal s _echo (t) can be expressed as:

Where A is the complex amplitude of the target echo signal, u(t) is the complex envelope of the reference signal, τ is the time delay of the target echo signal relative to the reference signal, and _fd is the Doppler frequency of the target echo signal.

S3: Estimate the number of multipath clutter signals in a monitoring channel using the baseband reference signal and the baseband monitoring signal.

It should be noted that the multipath clutter signal s _m (t) in the monitoring channel can be regarded as a reference signal with a certain delay and a certain amplitude, and can therefore be expressed as:

Wherein, _ωm is the complex amplitude of the m-th multipath clutter signal, _Δtm is the time delay of the m-th multipath clutter signal relative to the reference signal, and M is the number of multipath clutter signals.

The existing time domain projection clutter cancellation method can cancel multipath clutter within the delay unit order K. Usually, the value of K is large, resulting in a large number of signals in the multipath clutter subspace and high subsequent calculation complexity. If the number of multipath clutter signals can be estimated in advance, a large number of redundant calculations can be avoided. Multipath clutter signals can be regarded as reference signals with a certain delay and amplitude. Therefore, the multipath clutter signal and the reference signal are correlated in time, and the number of multipath clutter signals can be determined by the number of cross-correlation peaks between the reference signal and the monitoring signal (the monitoring signal contains the multipath clutter signal). However, when the time delays of two or more multipath clutter signals are very close, there may be only one correlation peak in the cross-correlation result, so it is necessary to estimate the upper limit of the number of multipath clutter signals based on the number of correlation peaks.

Specifically, step S3 of this embodiment includes the following sub-steps:

S3a: Calculate the cross-correlation function between the baseband reference signal and the baseband monitoring signal:

χ ₀ (n)=IFFT{FFT[s _ref (n),2N]·FFT ^* [s _surv (n),2N]}

Wherein, n is a discrete time point, s _ref (n) is a discretized representation of a baseband reference signal s _ref (t), s _surv (n) is a discretized representation of a baseband monitoring signal s _surv (t), N is the length of the baseband reference signal and the baseband monitoring signal, FFT(·) represents Fourier transform, IFFT(·) represents inverse Fourier transform, refer to FIG3 , FIG3 is a slice diagram of a zero-frequency mutual ambiguity function before clutter cancellation is performed using the cancellation method according to an embodiment of the present invention, that is, a cross-correlation result of a reference signal and a monitoring signal.

S3b: Record the average value of the correlation result of the cross-correlation function χ ₀ (n) in the delay unit [d _min , d _max ] exceeding the detection threshold _Th . Please refer to FIG4 , which is a schematic diagram of the cross-correlation result exceeding the detection threshold in the delay unit. In FIG4 , the average value of the data in the upper part of the area surrounded by d _min , d _max and _Th is

A _ve =mean(χ ₀ (n)>T _h ).

S3c: The part of the correlation results of χ ₀ (n) in the delay unit [d _min ,d _max ] exceeding γ·A _ve is formed into a new array χ ₁ , where γ is a constant factor, and the value of this embodiment is 1.75.

S3d: Count the number of maximum values cnt in the new array χ ₁ , and then the estimated number of multipath clutter signals can be obtained, that is, the upper limit of the number of multipath clutter signals is M ₀ =η·cnt, where η is a constant factor, and the value is 2 in this embodiment.

S4: According to the estimated number of multipath clutter signals, the multipath clutter signals are sparsely matched and cancelled using the orthogonal matching pursuit method to obtain multipath clutter sparse coefficients.

Multipath clutter signals can be regarded as reference signals with certain delay and amplitude. Therefore, the reference signal can be used to add delay to construct a multipath clutter subspace, and the multipath clutter signals can be eliminated by projecting them on the multipath clutter subspace. In the projection process, the number of multipath clutter signals estimated by S3 and the orthogonal matching pursuit method can greatly reduce the amount of calculation, and there is no need to require that any two clutter signals in the clutter subspace are orthogonal to each other.

Specifically, step S4 of this embodiment includes:

S4a: Generate a multipath clutter word space matrix D according to the discretized baseband reference signal s _ref (n):

Wherein, K=d _max -d _min , n represents discrete time, N represents signal length, _fs represents sampling frequency of external radiation source radar receiver, and there are d _min zeros before s _ref (1) in the first column of matrix D, and there are K+d _min +1 zeros before s _ref (1) in the last column.

S4b: Unitize each column of the multipath clutter word space matrix D:

D＝[a ₁ ,a ₂ ,…,a _K+1 ]，

Wherein, a _i (i=1,...,K+1) represents the normalized multipath clutter signal.

S4c: Initialize the residual signal after cancellation r ₀ =s _surv , and initialize the multipath clutter matrix index set Λ and the number of iterations m: m=1.

S4d: Calculate the position index λ _m of the current multipath clutter signal in the multipath clutter word space matrix D, that is, the position corresponding to the normalized multipath clutter signal with the largest correlation between the residual signal and the multipath clutter word space matrix D, expressed as:

Wherein, m represents the number of iterative cycles, for example, r ₀ represents the residual signal in the first cycle, and r ₁ represents the residual signal in the second cycle.

S4e: Add the obtained position index λ _m to the multipath clutter matrix index set

Λ _m = Λ _m-1 ∪{λ _m };

S4f: Update the residual signal using the multipath clutter matrix index set:

in, is part of the multipath clutter word space matrix D, It is a new spatial matrix composed of column signals corresponding to the index set Λ _m .

Assume that the multipath clutter word space matrix D has 10 columns of signals and the index set Λ _m = {2, 4, 7}, then It is the new matrix composed of the signals in the 2nd, 4th and 7th columns of D.

S4g: Let m = m + 1, repeat steps S4d-S4g, and when the iteration exit condition m = M ₀ is met, exit the loop and obtain the multipath clutter word space matrix after iterative update Wherein, M ₀ is the upper limit of the number of multipath clutter signals estimated in step S3.

S4h: Using the iteratively updated multipath clutter word space matrix Calculate the multipath clutter sparse coefficient:

Wherein, s _surv represents the baseband monitoring signal.

S5: Perform sparse matching cancellation on the multipath clutter using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation:

The following is a simulation experiment to further illustrate the effect of the method for canceling multipath clutter in the external radiation source radar monitoring channel signal of the embodiment of the present invention. The signal selected in this embodiment is a digital television live satellite signal (DVB-S), and the relevant parameters are shown in Table 1.

Table 1. Parameters related to the embodiments of the present invention

parameter Value f _s 100MHz d _min 10 d _max 500 τ 10.10us f _d 0Hz M 16 T _h 13dB γ 1.75 η 2

Table 2. Interference-to-signal ratio of multipath clutter signals

Multipath No. 1 2 3 4 5 6 7 8 Interference-to-signal ratio(dB) 16.99 25.54 24.12 18.14 25.52 18.53 25.03 22.52 Multipath No. 8 10 11 12 13 14 15 16 Interference-to-signal ratio(dB) 24.48 25.35 20.27 19.57 25.96 26.93 26.91 23.31

The interference signal ratio of 16 multipath clutters in the monitoring signal of this embodiment is shown in Table 2. The signal-to-noise ratio of the target echo signal is -35dB. By calculating the mutual ambiguity function (i.e., the cross-correlation result) of the monitoring signal and the reference signal at zero frequency, the ambiguity result shown in Figure 3 is obtained, and the upper limit of the number of multipath signals M ₀ =24 is obtained by step S3. Figure 5 is the mutual ambiguity function of the signal after multipath clutter cancellation in step S4 and the reference signal at the target echo Doppler frequency. It can be seen that the method of the embodiment of the present invention has a very ideal effect on multipath clutter cancellation, and the signal-to-noise ratio of the accumulated target echo signal is improved by 14.32dB.

In the orthogonal matching pursuit multipath clutter cancellation method adopted in the embodiment of the present invention, the dimension of the clutter filter matrix is only related to the number of multipath clutter contained in the monitoring channel signal, while the filter matrix of the existing method is the entire dictionary matrix. Therefore, the method proposed in the embodiment of the present invention can greatly reduce the complexity of solving the sparse matching coefficient and improve the calculation efficiency. In addition, the multipath clutter cancellation method in the embodiment of the present invention has no special requirements on the correlation of the column vectors of the multipath clutter filter matrix, while the existing multipath clutter cancellation method needs to ensure that the column vectors of the filter matrix are not correlated with each other. Therefore, the method proposed in the embodiment of the present invention is applicable to more practical application scenarios.

Another embodiment of the present invention provides a storage medium, wherein a computer program is stored in the storage medium, and the computer program is used to execute the steps of the method for canceling multipath clutter in the monitoring channel signal of the external radiation source radar described in the above embodiment. Another aspect of the present invention provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor calls the computer program in the memory, the steps of the method for canceling multipath clutter in the monitoring channel signal of the external radiation source radar described in the above embodiment are implemented. Specifically, the above-mentioned integrated module implemented in the form of a software function module can be stored in a computer-readable storage medium. The above-mentioned software function module is stored in a storage medium, including several instructions for enabling an electronic device (which can be a personal computer, a server, or a network device, etc.) or a processor (processor) to execute some steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk.

The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims (7)

1. A method for canceling multipath clutter in an external radiation source radar monitoring channel signal, characterized in that it comprises: S1: using a reference channel and a monitoring channel of an external radiation source radar to obtain a reference signal and a monitoring signal respectively, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target; S2: down-converting the reference signal and the monitoring signal to obtain a down-converted baseband reference signal and a baseband monitoring signal; S3: using the baseband reference signal and the baseband monitoring signal to estimate the number of multipath clutter signals in the monitoring channel; S4: according to the estimated number of multipath clutter signals, using the orthogonal matching pursuit method to perform sparse matching cancellation on the multipath clutter signals to obtain multipath clutter sparse coefficients; S5: performing sparse matching cancellation on the multipath clutter using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation. The S4 includes: S4a: Generate a multipath clutter word space matrix D according to the discretized baseband reference signal s _ref (n): Wherein, K=d _max -d _min , d _min and d _max represent the minimum and maximum values of the delay unit, respectively, n represents discrete time, N represents the length of the baseband reference signal and the baseband monitoring signal, f _s represents the sampling frequency of the external radiation source radar receiver, and there are d _min zeros before s _ref (1) in the first column of the matrix D, and there are K+d _min +1 zeros before s _ref (1) in the last column; S4b: Unitize each column of the multipath clutter word space matrix D: D＝[a ₁ ,a ₂ ,…,a _K ]， Wherein, a _i represents the normalized multipath clutter signal, i=1,...,K; S4c: Initialize the residual signal after cancellation r ₀ =s _surv , and initialize the multipath clutter matrix index set Λ and the number of iterations m: m=1, where s _surv represents the baseband monitoring signal; S4d: Calculate the position index λ _m of the current multipath clutter signal in the multipath clutter word space matrix D: Where m represents the number of iterations; S4e: Add the obtained position index λ _m to the multipath clutter matrix index set: Λ _m = Λ _m-1 ∪{λ _m }; S4f: Update the residual signal using the multipath clutter matrix index set: in, is part of the multipath clutter word space matrix D, is a new spatial matrix composed of column signals corresponding to the index set Λ _m ; S4g: Let m = m + 1, repeat steps S4d-S4g, and exit the loop when the iteration exit condition m = M ₀ is met to obtain the multipath clutter word space matrix after iterative update Where M ₀ is the number of estimated multipath clutter signals; S4h: Using the iteratively updated multipath clutter word space matrix Calculate the multipath clutter sparse coefficient: Wherein, s _surv represents the baseband monitoring signal. 2. The method for canceling multipath clutter in an external radiation source radar monitoring channel signal according to claim 1, characterized in that said S1 comprises: S1a: Set the sampling frequency _fs and beam receiving direction of the external radiation source radar receiver Receiving bandwidth B and detection threshold _Th ; S1b: Setting the minimum value d _min and the maximum value d _max of the delay unit for the occurrence of multipath clutter signals according to the dual-base detection range of different scenarios; S1c: using the reference channel of the external radiation source radar to receive a reference signal, and using the monitoring channel of the external radiation source radar to receive a monitoring signal. 3. The method for canceling multipath clutter in an external radiation source radar monitoring channel signal according to claim 1, wherein S2 comprises: The received reference signal and monitoring signal are digitally down-converted to obtain the down-converted baseband reference signal sref(t) and baseband monitoring signal s _surv (t): s _surv (t)＝s _echo (t)+s _m (t)+w(t) Where _f0 is the center frequency of the baseband signal, s _echo (t) represents the target echo signal received by the monitoring channel, s _m (t) represents the multipath clutter signal received by the monitoring channel, w(t) is Gaussian white noise, represents the initial phase of the transmitted signal, and the target echo signal s _echo (t) is expressed as: Where A is the complex amplitude of the target echo signal, u(t) is the complex envelope of the reference signal, τ is the time delay of the target echo signal relative to the reference signal, and _fd is the Doppler frequency of the target echo signal. 4. The method for canceling multipath clutter in an external radiation source radar monitoring channel signal according to claim 1, wherein S3 comprises: S3a: Calculate the cross-correlation function between the baseband reference signal and the baseband monitoring signal: χ ₀ (n)=IFFT{FFT[s _ref (n),2N]·FFT ^* [s _surv (n),2N]} Wherein, n is a discrete time point, s _ref (n) is a discretized representation of a baseband reference signal s _ref (t), s _surv (n) is a discretized representation of a baseband monitoring signal s _surv (t), N is the length of the baseband reference signal and the baseband monitoring signal, FFT(·) represents Fourier transform, and IFFT(·) represents inverse Fourier transform; S3b: Record the average value of the part of the correlation result of the cross-correlation function χ ₀ (n) in the time delay unit [d _min , d _max ] that exceeds the detection threshold _Th : A _ve =mean(χ ₀ (n)>T _h ); S3c: The part of the correlation results of χ ₀ (n) in the delay unit [d _min ,d _max ] that exceeds γ·A _ve is formed into a new array χ ₁ , where γ is a constant factor; S3d: Count the number of maximum values cnt in the new array χ ₁ , and estimate the number of multipath clutter signals to be M ₀ =η·cnt, where η is a constant factor. 5. The method for canceling multipath clutter in the external radiation source radar monitoring channel signal according to claim 4, characterized in that said S5 comprises: The multipath clutter sparse coefficient is used to perform sparse matching cancellation on the multipath clutter to obtain a signal after multipath clutter cancellation: 6. A storage medium, characterized in that a computer program is stored in the storage medium, and the computer program is used to execute the steps of the method for canceling multipath clutter in the external radiation source radar monitoring channel signal as described in any one of claims 1 to 5. 7. An electronic device, characterized in that it includes a memory and a processor, wherein a computer program is stored in the memory, and when the processor calls the computer program in the memory, the steps of the method for canceling multipath clutter in the monitoring channel signal of an external radiation source radar as described in any one of claims 1 to 5 are implemented.