CN115453477B - Method for canceling multipath clutter in external radiation source radar monitoring channel signal - Google Patents
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Abstract
The invention discloses a method for canceling multipath clutter in an external radiation source radar monitoring channel signal, which comprises the following steps: respectively obtaining a reference signal and a monitoring signal by using a reference channel and a monitoring channel of an external radiation source radar; 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; estimating the number of multipath clutter signals in a monitoring channel by using the baseband reference signal and the baseband monitoring signal; according to the estimated number of the multipath clutter signals, performing sparse matching cancellation on the multipath clutter signals by using an orthogonal matching pursuit method to obtain multipath clutter sparse coefficients; and performing sparse matching cancellation on the multipath clutter by using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation. The dimension of the clutter filtering matrix is only related to the number of multipath clutter contained in the monitoring channel information, so that the complexity of solving the sparse matching coefficient can be greatly reduced, and the calculation efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of radar signal processing, and particularly relates to a cancellation method of multipath clutter in an external radiation source radar monitoring channel signal, which is used for accurately implementing cancellation of multipath clutter in an external radiation source radar system monitoring channel.
Background
The external radiation source radar is a new system radar for detecting targets by using third-party electromagnetic signals (such as digital broadcast television signals, communication or navigation satellite signals, global system for mobile communications and the like). External-source radars are generally equipped with a reference antenna that receives the source signal and a monitor antenna that receives the target echo signal, the signals received by the reference antenna and the monitor antenna being referred to as the reference signal and the monitor signal, respectively. Ideally, the reference signal is a pure radiation source signal, the monitoring signal only comprises the radiation source signal (i.e. the target echo signal) after the target is secondarily reflected, and the delay and Doppler frequency of the echo signal relative to the reference signal can be obtained by performing coherent accumulation on the reference signal and the monitoring signal. Based on the method, various applications such as detection, positioning, tracking and the like of the target can be realized. However, the actually received monitoring signals contain strong multipath clutter and direct waves, and the signals can generate a large number of false targets when coherently accumulated, so that the target detection of the external radiation source radar is difficult.
Currently, a relatively wide-range multipath clutter cancellation method is applied to a time domain adaptive filtering method, such as a minimum average method (LEAST MEAN Squares, LMS), a Normalized minimum average method (Normalized LEAST MEAN Squares, NLMS), a gradient adaptive grid method (GRADIENT ADAPTIVE LATTICE, GAL), a recursive least square method (Recursive Least Squares, RLS) and the like; time domain projection methods such as extended cancellation (Extensive Cancellation Algorithm, ECA), ECA-B (ECA-Batch), ECA-S (ECA-slip), ECA-C (ECA-Carrie), and the like. The adaptive filtering method is low in convergence speed, and the parameter value depends on historical experience; the time domain projection method has no convergence problem, but the calculated amount of inverting the matrix is large, and the solving speed is low.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for canceling multipath clutter in an external radiation source radar monitoring channel signal. The technical problems to be solved by the invention are realized by the following technical scheme:
The invention provides a method for canceling multipath clutter in an external radiation source radar monitoring channel signal, which comprises the following steps:
S1: respectively obtaining a reference signal and a monitoring signal by utilizing a reference channel and a monitoring channel of an external radiation source radar, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target;
S2: 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;
s3: estimating the number of multipath clutter signals in a monitoring channel by using the baseband reference signal and the baseband monitoring signal;
S4: according to the estimated number of the multipath clutter signals, performing sparse matching cancellation on the multipath clutter signals by using an orthogonal matching pursuit method to obtain multipath clutter sparse coefficients;
s5: and performing sparse matching cancellation on the multipath clutter by 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: setting the sampling frequency f s and the beam receiving direction of an external radiation source radar receiver Receiving a bandwidth B and a detection threshold T h;
S1b: setting a minimum value d min and a maximum value d max of a time delay unit in which the multipath clutter signals appear according to the double-base detection ranges of different scenes;
S1c: and receiving a reference signal by using the reference channel of the external radiation source radar, and receiving a monitoring signal by using the monitoring channel of the external radiation source radar.
In one embodiment of the present invention, the S2 includes:
Digital down-conversion is performed on the received reference signal and the monitoring signal to obtain a baseband reference signal s ref (t) and a baseband monitoring signal s surv (t) after down-conversion:
ssurv(t)＝secho(t)+sm(t)+w(t)
Wherein f 0 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 white gaussian noise, and s echo (t) represents:
Where a is the complex amplitude of the target echo signal, u (t) is the complex envelope of the reference signal, τ is the delay of the target echo signal relative to the reference signal, and f d is the doppler frequency of the target echo signal.
In one embodiment of the present invention, the S3 includes:
s3a: calculating a cross-correlation function of the baseband reference signal and the baseband monitor signal:
χ0(n)＝IFFT{FFT[sref(n),2N]·FFT*[ssurv(n),2N]}
Where N is a discrete point in time, 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 lengths of the baseband reference signal and the baseband monitoring signal, FFT (·) represents the fourier transform, IFFT (·) represents the inverse fourier transform;
S3b: recording the average value of the part of the correlation result of the cross-correlation function χ 0 (n) in the delay unit [ d min,dmax ] exceeding the detection threshold T h:
Ave＝mean(χ0(n)＞Th)；
S3c: the part of the correlation result of χ 0 (n) in the time delay unit [ d min,dmax ] exceeding gamma.A ve is formed into a new array χ 1, wherein gamma is a constant factor;
S3d: and counting the maximum number cnt in the new array χ 1, and estimating the number of multipath clutter signals to be M 0 =eta·cnt, wherein eta is a constant factor.
In one embodiment of the present invention, the S4 includes:
S4a: generating a multipath clutter word space matrix D according to the discretized baseband reference signal s ref (n):
Where k=d max-dmin, N denotes the discrete time, N denotes the signal length, f s denotes the sampling frequency of the external radiation source radar receiver, D min 0 s ref (1) before s ref (1) in the first column and k+d min +1 0 s before s ref (1) in the last column in the matrix D;
S4b: the unitized representation is carried out on each column of the multipath clutter word space matrix D:
D＝[a1,a2,…,aK]，
where a i represents a unitized multipath clutter signal, i=1,..k;
s4c: initializing a canceled residual signal r 0＝ssurv, and initializing a multipath clutter matrix index set lambda and the iteration number m: m＝1；
S4d: calculating the position index lambda m of the current multipath clutter signal in the multipath clutter word space matrix D:
wherein m represents the number of iterative cycles;
S4e: adding the obtained position index lambda m into a multipath clutter matrix index set
Λm＝Λm-1∪{λm}；
S4f: updating residual signals by using the multipath clutter matrix index set:
Wherein, Is part of a 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 step S4d-S4g, exit the loop when the iteration exit condition m=m 0 is satisfied, obtain the multipath clutter word space matrix after iteration update Where M 0 is the estimated number of multipath clutter signals.
S4h: using iterative updated multipath clutter word space matrixCalculating multipath clutter sparse coefficients:
where s surv denotes a baseband monitoring signal.
In one embodiment of the present invention, the S5 includes:
and performing sparse matching cancellation on the multipath clutter by using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation:
Another aspect of the present invention provides a storage medium having stored therein a computer program for performing the steps of the method of cancellation of multipath clutter in an external source radar surveillance channel signal as described in any of the above embodiments.
In a further aspect the invention provides an electronic device comprising a memory having a computer program stored therein and a processor which when invoked performs the steps of the method of cancellation of multipath clutter in an external source radar surveillance channel signal as in any of the embodiments described above.
Compared with the prior art, the invention has the beneficial effects that:
1. The method for canceling the multipath clutter by adopting the orthogonal matching pursuit has the advantages that the dimension of the clutter filtering matrix is only related to the quantity of the multipath clutter contained in the monitoring channel information, so that the complexity of solving the sparse matching coefficient can be greatly reduced, and the calculation efficiency is improved.
2. The orthogonal matching pursuit multipath clutter cancellation method adopted by the invention has no special requirement on the correlation of the column vectors of the multipath clutter filter matrix, so the method is suitable for more practical application scenes.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a flow chart of a method for canceling multipath clutter in an external radiation source radar surveillance channel signal according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a processing procedure of a method for canceling multipath clutter in an external radiation source radar monitoring channel signal according to an embodiment of the present invention;
FIG. 3 is a slice of the zero frequency mutual ambiguity function before clutter cancellation using the cancellation method of the present invention;
FIG. 4 is a schematic diagram of cross-correlation results within a specified delay cell exceeding a detection threshold;
FIG. 5 is a slice of a cross-ambiguity function after clutter cancellation using the cancellation method of an embodiment of the present invention.
Detailed Description
In order to further describe the technical means and effects adopted by the invention to achieve the preset aim, the following describes in detail the method for canceling multipath clutter in the external radiation source radar monitoring channel signal according to the invention with reference to the attached drawings and the detailed description.
The foregoing and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings. The technical means and effects adopted by the present invention to achieve the intended purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only, and are not intended to limit the technical scheme of the present invention.
It should be noted that in this document relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or device comprising the element.
The embodiment of the invention provides a method for canceling multipath clutter in an external radiation source radar monitoring channel signal, referring to fig. 1 and 2, the method for canceling multipath clutter comprises the following steps:
s1: the reference signal and the monitoring signal are obtained by using a reference channel and a monitoring channel of the external radiation source radar, respectively.
Specifically, step S1 of the present embodiment includes the following sub-steps:
S1a: setting the sampling frequency f s and the beam receiving direction of an external radiation source radar receiver Receiving parameters such as bandwidth B, detection threshold T h and the like.
S1b: setting the correlation parameters of the multipath clutter signals. Setting the minimum value d min and the maximum value d max of a time delay unit of the occurrence of multipath clutter signals according to the double-base detection range [ R min,Rmax ] of different scenes, namely
Wherein c is the speed of light, floor (·) represents rounding down.
S1c: and receiving a reference signal by using the reference channel of the external radiation source radar, and receiving a monitoring signal by using the monitoring channel of the external radiation source radar, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target.
As described above, the external-radiation-source radar is generally equipped with a reference antenna that receives a radiation source signal and a monitor antenna that receives a target echo signal, and signals received by the reference antenna and the monitor antenna are referred to as a reference signal and a monitor signal, respectively. Ideally, the reference signal is a clean radiation source signal, and the monitoring signal only includes the radiation source signal (i.e., the target echo signal) after the target is secondarily reflected. In practical cases, the received reference signal may be expressed as:
where u (t) is the complex envelope of the reference signal, f c is the carrier frequency of the transmitted signal, Is the initial phase of the transmitted signal and t represents time.
S2: and 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.
Specifically, the received high frequency reference signal and the 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
ssurv(t)＝secho(t)+sm(t)+w(t)
Where f 0 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 white gaussian 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 delay of the target echo signal relative to the reference signal, and f d is the doppler frequency of the target echo signal.
S3: and estimating the number of multipath clutter signals in a monitoring channel by 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 thus can be expressed as:
Wherein ω m is the complex amplitude of the mth multipath clutter signal, Δt m is the delay of the mth multipath clutter signal relative to the reference signal, and M is the number of multipath clutter signals.
The prior time domain projection clutter cancellation method can cancel multipath clutter of the delay unit within the order K. In general, the value of K is larger, so that the number of signals in the multipath mixed wave subspace is more, and the subsequent calculation complexity is high. If the number of multipath clutter signals can be estimated in advance, a large number of redundant computations can be avoided. The multipath clutter signal may be regarded as a reference signal having a certain delay and amplitude, so that the multipath clutter signal and the reference signal have a correlation in time, and the number of multipath clutter signals may be determined by the number of cross correlation peaks of the reference signal and the monitoring signal (the monitoring signal contains the multipath clutter signal). However, when the delays of two or more multipath clutter signals are very close, there may be only one correlation peak in the cross-correlation result, so the upper limit of the number of multipath clutter signals needs to be estimated according to the number of correlation peaks.
Specifically, step S3 of the present embodiment includes the following sub-steps:
s3a: calculating a cross-correlation function of the baseband reference signal and the baseband monitor signal:
χ0(n)＝IFFT{FFT[sref(n),2N]·FFT*[ssurv(n),2N]}
Where 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 lengths of the baseband reference signal and the baseband monitoring signal, FFT (·) is a fourier transform, IFFT (·) is an inverse fourier transform, please refer to fig. 3, and fig. 3 is a zero frequency mutual ambiguity function slice diagram before clutter cancellation by using the cancellation method according to the embodiment of the present invention, that is, a cross correlation result of the reference signal and the monitoring signal.
S3b: recording the average value of the correlation result of the cross-correlation function χ 0 (n) in the delay unit [ d min,dmax ] exceeding the detection threshold T h, referring to FIG. 4, FIG. 4 is a schematic diagram showing the cross-correlation result in the specified delay unit exceeding the detection threshold, in FIG. 4, the average value of the upper data of the area surrounded by d min,dmax and T h is
Ave＝mean(χ0(n)＞Th)。
S3c: the new array χ 1 is formed by the part of χ 0 (n) in the delay unit [ d min,dmax ] exceeding γ·a ve, where γ is a constant factor, and the value of this example is 1.75.
S3d: and counting the maximum number cnt in the new array χ 1 to obtain the estimated number of multipath clutter signals, namely, the upper limit of the number of the multipath clutter signals is M 0 =eta·cnt, wherein eta is a constant factor, and the value of the embodiment is 2.
S4: and according to the estimated number of the multipath clutter signals, performing sparse matching cancellation on the multipath clutter signals by using an orthogonal matching pursuit method to obtain multipath clutter sparse coefficients.
The multipath clutter signal can be regarded as a reference signal with a certain time delay and amplitude, so that the multipath clutter signal can be eliminated by utilizing the reference signal to add the time delay to construct a multipath clutter subspace and by projecting the multipath clutter signal on the multipath clutter subspace. In the projection process, the number of multipath clutter signals estimated by S3 and an orthogonal matching pursuit method can greatly reduce the calculated amount, and any two clutter signals in the clutter subspace are not required to be mutually orthogonal.
Specifically, step S4 of the present embodiment includes:
S4a: generating a multipath clutter word space matrix D according to the discretized baseband reference signal s ref (n):
Where k=d max-dmin, N denotes the discrete time, N denotes the signal length, f s denotes the sampling frequency of the external radiation source radar receiver, D min 0 s ref (1) in the first column and k+d min +1 0 s ref (1) in the last column in the matrix D.
S4b: each column of the multipath clutter word space matrix D is expressed in units:
D＝[a1,a2,…,aK+1]，
Where a i (i=1,., k+1) represents the unitized multipath clutter signal.
S4c: initializing a canceled residual signal r 0＝ssurv, and initializing a multipath clutter matrix index set lambda and the iteration number m:m＝1。
s4d: calculating a position index lambda m of the current multipath clutter signal in the multipath clutter word space matrix D, namely, the position corresponding to the unitized multipath clutter signal with the largest correlation in the multipath clutter word space matrix D, wherein the position index lambda m is expressed as:
where m represents the number of iterative loops, e.g., r 0 represents the residual signal at the first loop and r 1 represents the residual signal at the second loop.
S4e: adding the obtained position index lambda m into a multipath clutter matrix index set
Λm＝Λm-1∪{λm}；
S4f: updating residual signals by using the multipath clutter matrix index set:
Wherein, Is part of a multipath clutter word space matrix D,/>Is a new spatial matrix composed of column signals corresponding to the index set Λ m.
Assuming that the multipath clutter word space matrix D has 10 columns of signals, the index set Λ m = {2,4,7}, thenI.e. the new matrix of column 2, 4 and 7 signals inside D.
S4g: let m=m+1, repeat step S4d-S4g, when satisfying iteration exit condition m=m 0, exit the loop, obtain the multipath clutter word space matrix after iteration updateWherein M 0 is the upper limit of the number of multipath clutter signals estimated in step S3.
S4h: using iterative updated multipath clutter word space matrixCalculating multipath clutter sparse coefficients:
where s surv denotes a baseband monitoring signal.
S5: and performing sparse matching cancellation on the multipath clutter by using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation:
The effect of the cancellation method of multipath clutter in the external radiation source radar monitoring channel signal in the embodiment of the invention is further described below through simulation experiments. The signal selected in this embodiment is a digital television direct broadcast satellite signal (DVB-S), and the relevant partial parameters are shown in table 1.
TABLE 1 parameters related to the examples of the invention
| Parameters (parameters) | Value taking |
| fs | 100MHz |
| dmin | 10 |
| dmax | 500 |
| τ | 10.10us |
| fd | 0Hz |
| M | 16 |
| Th | 13dB |
| γ | 1.75 |
| η | 2 |
TABLE 2 interference to signal ratio of multipath clutter signals
| Multipath numbering | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Interference and signal ratio (dB) | 16.99 | 25.54 | 24.12 | 18.14 | 25.52 | 18.53 | 25.03 | 22.52 |
| Multipath numbering | 8 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
| Interference and signal ratio (dB) | 24.48 | 25.35 | 20.27 | 19.57 | 25.96 | 26.93 | 26.91 | 23.31 |
The interference ratio of 16 multipath clutter in the monitoring signal of this embodiment is shown in table 2. The signal-to-noise ratio of the target echo signal is-35 dB. The ambiguity result shown in fig. 3 is obtained by calculating the mutual ambiguity function (i.e., the cross correlation result) of the monitoring signal and the reference signal at zero frequency, and the upper limit M 0 =24 of the number of multipath signals is obtained by step S3. Fig. 5 shows a mutual ambiguity function of the signal after multipath clutter cancellation and the reference signal at the target echo doppler frequency in step S4, so that the method according to the embodiment of the invention has very ideal multipath clutter cancellation effect, and improves the signal-to-noise ratio after accumulating the target echo signal by 14.32dB.
According to the orthogonal matching pursuit multipath clutter cancellation method adopted by the embodiment of the invention, the dimension of the clutter filter matrix is only related to the number of multipath clutter contained in the monitoring channel information, and the filter matrix of the existing method is the whole dictionary matrix, so that the complexity of solving the sparse matching coefficient can be greatly reduced, and the calculation efficiency is improved. In addition, the multipath clutter cancellation method of the embodiment of the invention has no special requirement on the correlation of the column vectors of the multipath clutter filter matrix, and the conventional multipath clutter cancellation method needs to ensure that the column vectors of the filter matrix are not correlated with each other, so the method provided by the embodiment of the invention is suitable for more practical application scenes.
A further embodiment of the present invention provides a storage medium having stored therein a computer program for executing the steps of the method for canceling multipath clutter in an external source radar surveillance channel signal described in the above embodiment. In yet another aspect, the present invention provides an electronic device, including a memory and a processor, where the memory stores a computer program, and the processor when calling the computer program in the memory implements the steps of the method for canceling multipath clutter in an external radiation source radar surveillance channel signal according to the above embodiment. In particular, the integrated modules described above, implemented in the form of software functional modules, may be stored in a computer readable storage medium. The software functional module is stored in a storage medium and includes instructions for causing an electronic device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to perform part of the steps of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (7)
1. A method for canceling multipath clutter in an external radiation source radar surveillance channel signal, comprising:
S1: respectively obtaining a reference signal and a monitoring signal by utilizing a reference channel and a monitoring channel of an external radiation source radar, wherein the monitoring signal is a signal received by the monitoring channel after being reflected by a target;
S2: 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;
s3: estimating the number of multipath clutter signals in a monitoring channel by using the baseband reference signal and the baseband monitoring signal;
S4: according to the estimated number of the multipath clutter signals, performing sparse matching cancellation on the multipath clutter signals by using an orthogonal matching pursuit method to obtain multipath clutter sparse coefficients;
S5: performing sparse matching cancellation on the multipath clutter by using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation,
The step S4 comprises the following steps:
S4a: generating a multipath clutter word space matrix D according to the discretized baseband reference signal s ref (n):
Wherein k=d max-dmin,dmin and D max represent the minimum value and the maximum value of the delay unit respectively, N represents the discrete time, N represents the lengths of the baseband reference signal and the baseband monitoring signal, f s represents the sampling frequency of the radar receiver of the external radiation source, D min 0 s are in front of s ref (1) in the first column and k+d min +10 s in front of s ref (1) in the last column in the matrix D;
S4b: the unitized representation is carried out on each column of the multipath clutter word space matrix D:
D＝[a1,a2,…,aK]，
where a i represents a unitized multipath clutter signal, i=1,..k;
s4c: initializing a canceled residual signal r 0＝ssurv, and initializing a multipath clutter matrix index set lambda and the iteration number m: m=1, wherein s surv represents a baseband monitoring signal;
S4d: calculating the position index lambda m of the current multipath clutter signal in the multipath clutter word space matrix D:
wherein m represents the number of iterative cycles;
s4e: adding the obtained position index lambda m into a multipath clutter matrix index set:
Λm＝Λm-1∪{λm}；
S4f: updating residual signals by using the multipath clutter matrix index set:
Wherein, Is part of a 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 step S4d-S4g, exit the loop when the iteration exit condition m=m 0 is satisfied, obtain the multipath clutter word space matrix after iteration update Wherein M 0 is the estimated number of multipath clutter signals;
S4h: using iterative updated multipath clutter word space matrix Calculating multipath clutter sparse coefficients:
where s surv denotes a baseband monitoring signal.
2. The method for canceling multipath clutter in an external source radar surveillance channel signal according to claim 1, wherein S1 comprises:
S1a: setting the sampling frequency f s and the beam receiving direction of an external radiation source radar receiver Receiving a bandwidth B and a detection threshold T h;
S1b: setting a minimum value d min and a maximum value d max of a time delay unit in which the multipath clutter signals appear according to the double-base detection ranges of different scenes;
S1c: and receiving a reference signal by using the reference channel of the external radiation source radar, and receiving a monitoring signal by using the monitoring channel of the external radiation source radar.
3. The method for cancellation of multipath clutter in an external source radar surveillance channel signal according to claim 1, wherein S2 comprises:
digital down-conversion is performed on the received reference signal and the monitoring signal to obtain a baseband reference signal sref (t) and a baseband monitoring signal s surv (t) after down-conversion:
ssurv(t)＝secho(t)+sm(t)+w(t)
Where f 0 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 white gaussian noise, Representing an initial phase of the transmit signal, the target echo signal s echo (t) is represented 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 delay of the target echo signal relative to the reference signal, and f d is the doppler frequency of the target echo signal.
4. The method for cancellation of multipath clutter in an external source radar surveillance channel signal according to claim 1, wherein S3 comprises:
s3a: calculating a cross-correlation function of the baseband reference signal and the baseband monitor signal:
χ0(n)＝IFFT{FFT[sref(n),2N]·FFT*[ssurv(n),2N]}
Where N is a discrete point in time, 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 lengths of the baseband reference signal and the baseband monitoring signal, FFT (·) represents the fourier transform, IFFT (·) represents the inverse fourier transform;
S3b: recording the average value of the part of the correlation result of the cross-correlation function χ 0 (n) in the delay unit [ d min,dmax ] exceeding the detection threshold T h:
Ave＝mean(χ0(n)>Th)；
S3c: the part of the correlation result of χ 0 (n) in the time delay unit [ d min,dmax ] exceeding gamma.A ve is formed into a new array χ 1, wherein gamma is a constant factor;
S3d: and counting the maximum number cnt in the new array χ 1, and estimating the number of multipath clutter signals to be M 0 =eta·cnt, wherein eta is a constant factor.
5. The method for canceling multipath clutter in an external source radar surveillance channel signal according to claim 4, wherein S5 comprises:
and performing sparse matching cancellation on the multipath clutter by using the multipath clutter sparse coefficient to obtain a signal after multipath clutter cancellation:
6. A storage medium having stored therein a computer program for performing the steps of the method of cancellation of multipath clutter in an external source radar surveillance channel signal according to any of claims 1 to 5.
7. An electronic device comprising a memory and a processor, the memory having stored therein a computer program, the processor implementing the steps of the method for canceling multipath clutter in an external source radar surveillance channel signal according to any of claims 1 to 5 when the computer program in the memory is invoked by the processor.
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