CN111580107B - Radio frequency interference suppression method and device for SAR echo signal and imaging method - Google Patents

Abstract

The invention discloses a radio frequency interference suppression method, device and imaging method of a SAR echo signal. The radio frequency interference suppression method of a SAR echo signal includes: performing range-to-Fourier transform on the received initial echo signal to obtain an initial Spectrum; performing notch processing on the initial spectrum based on the preset notch interference detection threshold to obtain a notch-processed spectrum; filtering the notch-processed spectrum to obtain a filtered spectrum; based on the preset The prediction model performs spectrum extrapolation processing on the filtered spectrum to obtain forward extrapolated spectral data and backward extrapolated spectral data; reconstructs based on forward extrapolated spectral data, backward extrapolated spectral data and filtered spectrum processing to obtain the target spectrum without loss; based on the target spectrum without loss, the frequency modulation information of the range signal is recovered, and the target echo signal with suppressed interference and complete spectrum is obtained. The invention can accurately suppress the radio frequency interference.

Description

A method, device and imaging method for suppressing radio frequency interference of SAR echo signal

Technical Field

The present invention relates to the cross-technical field of aerospace and microwave remote sensing, and in particular to a method and device for suppressing radio frequency interference of SAR echo signals and an imaging method.

Background Art

SAR (Synthetic Aperture Radar) technology is an active aerospace and aviation remote sensing method. Microwave imaging technology has the characteristics of working all day and all weather. It has been widely used in environmental protection, disaster monitoring, ocean observation, resource exploration, precision agriculture, geological mapping, etc., and has become one of the most important means of high-resolution earth observation and global resource management. However, SAR is easily affected by RFI (Radio Frequency Interference) in complex electromagnetic environments, especially in low bands (L band, P band), which reduces image quality and affects target detection and image recognition.

The operating frequency of low-frequency SAR is VHF (Very High Frequency) or UHF (Ultra High Frequency) band. Since this band was first allocated by ITU (International Telecommunications Union) to terrestrial broadcasting and television systems, communication systems, GPS (Global Positioning System) and ground warning radar, even if many anti-interference technologies are considered in the design of the SAR system, there are still a large number of interference signals entering the SAR system receiver, which ultimately leads to a decrease in the imaging quality of the SAR system.

The existing RFI suppression methods mainly include: frequency domain notch method, subspace decomposition method, interference extraction method, etc. Since the traditional frequency domain notch method easily causes the loss of useful signals, and the subspace projection method is overly dependent on the orthogonality of the subspace, when the interference signal power is large, it will cause subspace misjudgment. In addition, the calculation complexity of the interference extraction method is too high, the mathematical model of radio frequency interference is quite complex, and there will be model mismatch, resulting in model parameter estimation errors, which will lead to inaccurate RFI estimation.

Summary of the invention

The purpose of the embodiments of the present invention is to provide a method, device and imaging method for radio frequency interference suppression of SAR echo signals, so as to solve the problem that radio frequency interference suppression is not accurate enough in the prior art.

In order to solve the above technical problems, the embodiments of the present application adopt the following technical solutions: a method for suppressing radio frequency interference of SAR echo signals, comprising the following steps:

Performing a range-direction Fourier transform on the received initial echo signal to obtain an initial frequency spectrum corresponding to the initial echo signal;

Performing notch processing on the initial spectrum based on a preset notch interference detection threshold value to obtain a spectrum after notch processing;

Performing filtering on the frequency spectrum after the notch processing to obtain a filtered frequency spectrum;

Performing spectrum extrapolation processing on the filtered spectrum based on a preset prediction model to obtain forward extrapolated spectrum data and backward extrapolated spectrum data;

Performing reconstruction processing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without missing components;

The frequency modulation information of the range signal is restored based on the target spectrum without missing any, so as to obtain a target echo signal with suppressed interference and complete spectrum.

Optionally, performing notch processing on the initial spectrum based on a preset notch interference detection threshold value to obtain a spectrum after notch processing specifically includes:

Performing notch processing on the initial spectrum based on a preset first notch interference detection threshold value to obtain a first spectrum;

The first frequency spectrum is notched based on a preset second notch interference detection threshold value to obtain the notched frequency spectrum.

Optionally, the reconstructing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without missing specifically includes:

Reconstructing the missing spectrum based on the forward extrapolated spectrum and the backward extrapolated spectrum to obtain the missing spectrum;

A splicing process is performed based on the filtered spectrum and the missing spectrum to obtain the target spectrum without missing anything.

Optionally, the prediction model includes an AR linear prediction model; the method further includes constructing the AR linear prediction model, specifically including:

Determine the order of the AR linear prediction model based on the number of distance sampling points;

Calculating the coefficients of the AR linear prediction model based on a preset calculation method;

The AR linear prediction model is constructed based on the order and coefficients.

Optionally, the preset method includes one or more of the following: a Berg algorithm and an improved covariance algorithm.

An embodiment of the present application provides a SAR echo signal radio frequency interference suppression device, comprising:

A transformation module, used for performing a range-oriented Fourier transform on the received initial echo signal to obtain an initial spectrum corresponding to the initial echo signal;

A notch processing module, used to perform notch processing on the initial spectrum based on a preset notch interference detection threshold value to obtain a spectrum after notch processing;

A filtering processing module, used for filtering the spectrum after the notch processing to obtain a filtered spectrum;

A spectrum extrapolation processing module, used for performing spectrum extrapolation processing on the spectrum after filtering based on a preset prediction model to obtain forward extrapolated spectrum data and backward extrapolated spectrum data;

A reconstruction module, used for performing reconstruction processing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without missing components;

The recovery module is used to recover the frequency modulation information of the range signal based on the target spectrum without missing any, so as to obtain the target echo signal with suppressed interference and complete spectrum.

Optionally, the notch processing module is specifically used for:

Performing notch processing on the initial spectrum based on a preset first notch interference detection threshold value to obtain a first spectrum;

The first frequency spectrum is notched based on a preset second notch interference detection threshold value to obtain the notched frequency spectrum.

Optionally, the reconstruction module is specifically used for:

Reconstructing the missing spectrum based on the forward extrapolated spectrum and the backward extrapolated spectrum to obtain the missing spectrum;

A splicing process is performed based on the filtered spectrum and the missing spectrum to obtain the target spectrum without missing anything.

Optionally, the prediction model includes an AR linear prediction model; the device further includes a construction module for constructing the AR linear prediction model, and the construction module is specifically used to:

Determine the order of the AR linear prediction model based on the number of distance sampling points;

Calculating the coefficients of the AR linear prediction model based on a preset calculation method;

The AR linear prediction model is constructed based on the order and coefficients.

The embodiment of the present application provides an imaging method, comprising the following steps:

Obtain corresponding two-dimensional SAR data based on a target echo signal obtained by the radio frequency interference suppression method for SAR echo signals described in any one of the above items;

The two-dimensional SAR data is used to perform imaging processing on the target object.

The present invention can accurately suppress radio frequency interference by performing notch processing on the echo signal and performing spectrum extrapolation processing on the spectrum after notching, thereby solving the problem of inaccurate radio frequency interference suppression in the prior art. At the same time, the method in the present application overcomes the technical defect of detail loss in the traditional notch method, which is beneficial to subsequent imaging based on SAR data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for suppressing radio frequency interference of a SAR echo signal according to an embodiment of the present invention;

FIG2 is a structural block diagram of a device for suppressing radio frequency interference of SAR echo signals according to another embodiment of the present invention;

FIG. 3 is a flow chart of another embodiment of an imaging method according to the present invention.

DETAILED DESCRIPTION

Various aspects and features of the present application are described herein with reference to the accompanying drawings.

It should be understood that various modifications may be made to the embodiments of the present application. Therefore, the above description should not be considered as limiting, but only as an example of the embodiments. Other modifications within the scope and spirit of the present application will occur to those skilled in the art.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

These and other characteristics of the present application will become apparent from the following description of a preferred form of embodiment given as a non-limiting example with reference to the accompanying drawings.

It should also be understood that, although the present application has been described with reference to some specific examples, those skilled in the art will be able to implement many other equivalent forms of the present application that have the features described in the claims and are therefore within the scope of protection defined thereby.

The above and other aspects, features and advantages of the present application will become more apparent in view of the following detailed description when taken in conjunction with the accompanying drawings.

Specific embodiments of the present application are described hereinafter with reference to the accompanying drawings; however, it should be understood that the embodiments applied for are merely examples of the present application, which may be implemented in a variety of ways. Well-known and/or repeated functions and mechanisms are not described in detail to avoid unnecessary or redundant details that obscure the present application. Therefore, the specific structural and functional details applied for herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use the present application in a variety of ways with substantially any suitable detailed mechanism.

This specification may use the phrases "in one embodiment," "in another embodiment," "in yet another embodiment," or "in other embodiments," all of which may refer to one or more of the same or different embodiments according to the present application.

The embodiment of the present invention provides a method for suppressing radio frequency interference of a SAR echo signal, comprising the following steps:

Step S101, performing a range Fourier transform on the received initial echo signal to obtain an initial frequency spectrum corresponding to the initial echo signal;

In the specific implementation process, this step is to perform a range Fourier transform on the received initial echo signal, i.e., the SAR echo signal x(n), to obtain an echo signal X(n) in the azimuth time domain and range frequency domain, i.e., the initial spectrum, which can also be called the echo range line spectrum, where _-Nr / _2≤n≤Nr /2-1, and _Nr represents the number of sampling points in the range direction.

Step S102, performing notch processing on the initial spectrum based on a preset notch interference detection threshold value to obtain a spectrum after notch processing;

In the specific implementation process of this step, it is necessary to first perform notch processing on the initial spectrum based on the preset first notch interference detection threshold value to obtain the first spectrum; and then perform notch processing on the first spectrum based on the preset second notch interference detection threshold value to obtain the notch-processed spectrum. That is, the initial spectrum is notched twice.

More specifically, the initial spectrum is firstly notched by the first threshold, and the specific steps are as follows: Calculate the first notch interference detection threshold value λ ₁ , and the calculation formula is:

λ ₁ ＝μ ₁ +σ ₁ (1)

Wherein, μ ₁ represents the mean of the echo range line spectrum; X(n) represents the spectrum of the echo range line signal, i.e., the initial spectrum; σ ₁ represents the standard deviation of the echo range line spectrum; N _r represents the number of sampling points in the range direction; and N ₀ represents the number of transition zone points.

After obtaining λ ₁ by using the above calculation formula, the initial spectrum X(n) can be notched for the first time based on λ ₁ , that is, the signal sampling points satisfying |X(n)|＞λ ₁ are set to zero, and the first spectrum X ₁ (n) of the echo signal after the first notch is obtained:

Where X(n) represents the frequency spectrum of the echo range line, λ ₁ represents the threshold value of the first notch, and |·| represents the absolute value of the signal.

After obtaining the first spectrum X ₁ (n), the echo signal can be subjected to a second threshold notch. The specific steps are as follows: First, the second notch interference detection threshold λ ₂ is calculated. The calculation formula is:

λ ₂ =μ ₂ +σ ₂ (5)

Among them, μ ₂ represents the mean of the non-zero spectrum after the first notch; X ₁ (n) represents the spectrum of the echo signal after one notch, that is, the first spectrum; σ ₂ represents the standard deviation of the non-zero spectrum after the first notch; N ₁ is the number of interference frequency points set to zero after the first notch; N _r represents the number of sampling points in the range direction; N ₀ represents the number of transition band points.

Perform a second notch on the echo signal spectrum, that is, set the signal sampling points satisfying |X ₁ (n)|＞λ ₂ to zero, and obtain the spectrum X ₂ (n) of the echo signal after the second notch:

Wherein, X ₁ (n) represents the range line spectrum of the echo signal after the first notch, X(n) represents the spectrum of the echo range line, λ ₂ represents the threshold value of the second notch, and |·| represents the absolute value of the signal.

After the second notch interference detection threshold λ ₂ is calculated, the first spectrum X ₁ (n) can be notched for the second time based on λ ₂ , that is, signal sampling points satisfying |X ₁ (n)|>λ ₂ are set to zero to obtain the spectrum X ₂ (n) of the echo signal after the second notch processing.

Step S103, filtering the spectrum after the notch processing to obtain a filtered spectrum;

In the specific implementation process of this step, after obtaining the spectrum X ₂ (n) after notch processing, X ₂ (n) can be subjected to range matched filtering to obtain the spectrum X ₃ (n) after matched filtering, and the formula is:

X ₃ (n) = X ₂ (n)·H (f) (9)

Among them, the matched filter H(f) is:

Wherein, rect(·) represents the rectangular window function, X ₂ (n) is the frequency spectrum of the echo signal after the secondary notch, f is the range frequency, K _r is the range modulation frequency, and _Br is the signal bandwidth.

Step S104, performing spectrum extrapolation processing on the filtered spectrum based on a preset prediction model to obtain forward extrapolated spectrum data and backward extrapolated spectrum data;

The prediction module in this step includes an AR linear prediction model. The AR linear prediction model is pre-constructed, and the construction steps include: determining the order of the AR linear prediction model based on the number of distance sampling points; calculating the coefficients of the AR linear prediction model based on a preset calculation method; and constructing the AR linear prediction model based on the order and coefficients.

More specifically, in this embodiment, before performing spectrum extrapolation processing, it is necessary to first determine the AR linear prediction model order M and coefficient a(m) to construct the AR linear prediction model. That is, the AR linear prediction model order is determined based on the number of sampling points in the distance direction. The number of sampling points in the distance direction is N _r , and the AR linear prediction model order M generally takes a value between N _r /3 and N _r /2. The coefficient a(m) of the AR linear prediction model can be calculated using methods such as the Burg algorithm and the improved covariance.

After determining the AR linear prediction model order M and coefficient a(m), the prediction module can be used to extrapolate the missing spectrum based on the filtered spectrum X ₃ (n) to obtain the forward extrapolated spectrum X ₄ (n) and the backward extrapolated spectrum X ₅ (n). The forward extrapolated spectrum X ₄ (n) and the backward extrapolated spectrum X ₅ (n) are specifically calculated using two formulas of the AR linear prediction module, as follows:

Wherein, X ₃ (n) represents the spectrum after range matched filtering; M represents the prediction model order; a(m) represents the prediction model coefficient; a ^* (m) represents the conjugate complex number of the prediction model coefficient; f _Low,l and f _Hig,l represent the lowest frequency and the highest frequency of the lth missing spectrum gap respectively; Δf represents the frequency sampling interval.

Step S105, performing reconstruction processing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without missing components;

In the specific implementation process of this step, it is necessary to first reconstruct the missing spectrum based on the forward extrapolated spectrum and the backward extrapolated spectrum to obtain the missing spectrum; and then perform splicing processing based on the filtered spectrum and the missing spectrum to obtain the target spectrum without missing spectrum.

计算公式为：More specifically, after obtaining the forward extrapolated spectrum X ₄ (n) and the backward extrapolated spectrum X ₅ (n), the forward extrapolated spectrum data X ₄ (n) and the backward extrapolated spectrum data X ₅ (n) can be weighted according to the following calculation formula to obtain the final result of missing data reconstruction:

The calculation formula is:

表示缺失频谱；N_Low,l和N_Hig,l分别表示第l个缺失频谱间隙的最低频率和最高频率对应的频点；X₃(n)表示距离向匹配滤波后的频谱；M表示预测模型阶数；a(m)表示预测模型系数；a^*(m)表示预测模型系数的共轭复数；f_Low,l和f_Hig,l分别表示第l个缺失频谱间隙的最低和最高频率；Δf表示频率采样间隔。in,

represents the missing spectrum; N _Low,l and N _Hig,l represent the frequency points corresponding to the lowest frequency and the highest frequency of the lth missing spectrum gap respectively; X ₃ (n) represents the spectrum after distance matching filtering; M represents the prediction model order; a(m) represents the prediction model coefficient; a ^* (m) represents the conjugate complex number of the prediction model coefficient; f _Low,l and f _Hig,l represent the lowest and highest frequencies of the lth missing spectrum gap respectively; Δf represents the frequency sampling interval.

后，就可以基于该获得缺失频谱

以及滤波后的频谱X₃(n)利用如下公式来进行拼接处理，获得无缺失的目标频谱X₆(n)，公式为：In obtaining the missing spectrum

Then, the missing spectrum can be obtained based on

The filtered spectrum X ₃ (n) is concatenated using the following formula to obtain a target spectrum X ₆ (n) without missing components. The formula is:

Wherein, H ^* (f) is the complex conjugate of H(f), and X ₆ (n) is the signal spectrum after matched filtering without missing parts.

Step S106, recovering the frequency modulation information of the range signal based on the target spectrum without missing anything, to obtain a target echo signal with suppressed interference and complete spectrum.

After obtaining the target spectrum X ₆ (n) in this step, the frequency modulation information of the SAR data range signal can be restored by the following formula to obtain the target echo signal X ₇ (n) with suppressed interference and complete spectrum. The formula is:

X ₇ (n)＝X ₆ (n)·H ^* (f) (15)

Wherein, H ^* (f) is the complex conjugate of H(f), and X ₆ (n) is the signal spectrum after matched filtering without missing, that is, the target spectrum.

The present invention implements the method of adding spectrum extrapolation after the secondary notch to restore the spectrum after the notch, which can accurately suppress radio frequency interference and solve the problem of inaccurate radio frequency interference suppression in the prior art. The method of the present invention not only has the advantages of the traditional method, but also makes up for the shortcomings of the traditional method, which is conducive to improving the quality of SAR images and improving the recognition of details in the image. At the same time, the method of the present invention reduces the computational complexity and improves the computational efficiency.

Another embodiment of the present invention provides a SAR echo signal radio frequency interference suppression device, comprising:

Transformation module 1, used for performing range Fourier transform on the received initial echo signal to obtain an initial spectrum corresponding to the initial echo signal;

A notch processing module 2, configured to perform notch processing on the initial spectrum based on a preset notch interference detection threshold value to obtain a spectrum after notch processing;

A filtering processing module 3 is used to filter the spectrum after the notch processing to obtain a filtered spectrum;

The spectrum extrapolation processing module 4 is used to perform spectrum extrapolation processing on the spectrum after filtering based on a preset prediction model to obtain forward extrapolated spectrum data and backward extrapolated spectrum data;

A reconstruction module 5, configured to perform reconstruction processing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without missing components;

The recovery module 6 is used to recover the frequency modulation information of the range signal based on the target spectrum without missing any, so as to obtain the target echo signal with suppressed interference and complete spectrum.

In the specific implementation process of this embodiment, the notch processing module is specifically used to: perform notch processing on the initial spectrum based on a preset first notch interference detection threshold value to obtain a first spectrum; perform notch processing on the first spectrum based on a preset second notch interference detection threshold value to obtain the notch-processed spectrum.

In the specific implementation process of this embodiment, the reconstruction module is specifically used to: reconstruct the missing spectrum based on the forward extrapolated spectrum and the backward extrapolated spectrum to obtain the missing spectrum;

A splicing process is performed based on the filtered spectrum and the missing spectrum to obtain the target spectrum without missing anything.

In the specific implementation process of this embodiment, the prediction model includes an AR linear prediction model; the device also includes a construction module for constructing the AR linear prediction model, and the construction module is specifically used to: determine the order of the AR linear prediction model based on the number of distance sampling points; calculate the coefficients of the AR linear prediction model based on a preset calculation method; and construct the AR linear prediction model based on the order and coefficients. The preset calculation methods in this embodiment include: the Berg algorithm and the improved covariance algorithm.

The present invention implements the method of performing secondary notching post-processing on the initial spectrum by using a notch processing module and restoring the notched spectrum by using a spectrum extrapolation module, so as to accurately suppress radio frequency interference. The method of the present invention not only has the advantages of the traditional method, but also makes up for the shortcomings of the traditional method, is conducive to improving the quality of SAR images, and improves the recognition of details in the image. At the same time, the method of the present invention reduces the computational complexity and improves the computational efficiency.

Another embodiment of the present invention provides an imaging method, comprising: obtaining corresponding two-dimensional SAR data based on the target echo signal obtained by the above-mentioned SAR echo signal radio frequency interference suppression method; and performing imaging processing on the target object using the two-dimensional SAR data. Specifically, the method comprises the following steps:

Step S301, sampling echo data in each direction of the target object based on the sampling time to obtain initial echo signals corresponding to each direction;

Step S302, performing range Fourier transform on each of the initial echo signals to obtain an initial frequency spectrum corresponding to each of the initial echo signals;

Step S303, performing notch processing on each of the initial spectra based on a preset notch interference detection threshold value to obtain a notch-processed spectrum corresponding to each of the initial spectra;

Step S304, filtering each of the frequency spectra after notch processing to obtain a filtered frequency spectrum corresponding to each of the frequency spectra after notch processing;

Step S305, performing spectrum extrapolation processing on each of the filtered spectrums based on a preset prediction model to obtain forward extrapolated spectrum data and backward extrapolated spectrum data corresponding to each of the filtered spectrums;

Step S306, performing reconstruction processing based on each of the filtered spectra, the forward extrapolated spectrum data corresponding to the filtered spectrum, and the backward extrapolated spectrum data to obtain a target spectrum without missing parts corresponding to each of the initial echo signals;

Step S307 , recovering the frequency modulation information of the range signal based on each of the target frequency spectra without missing items, and obtaining the target echo signal corresponding to each of the initial echo signals.

Step S308, obtaining two-dimensional SAR data corresponding to the target object based on each of the target echo signals;

Step S309: performing imaging processing based on the two-dimensional SAR data to obtain a SAR image of the target object.

During the implementation of the embodiment of the present invention, the specific implementation process of step S302 to step S307 may include the steps in the method for suppressing radio frequency interference of SAR echo signals provided in the above embodiment, which will not be described in detail here.

The present invention implements spectrum extrapolation processing on the spectrum after the secondary notch, so that the spectrum after the notch can be restored, and the radio frequency interference is accurately suppressed, which is beneficial to improving the quality of the SAR image and improving the recognition of the details in the image. At the same time, the method of the present invention reduces the computational complexity and improves the operation efficiency. A better imaging effect can be obtained in a shorter time, that is, the imaging effect and the operation efficiency are improved at the same time.

The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims (8)

1. A radio frequency interference suppression method of SAR echo signals is characterized by comprising the following steps:

carrying out distance Fourier transform on the received initial echo signal to obtain an initial frequency spectrum corresponding to the initial echo signal;

performing notch processing on the initial frequency spectrum based on a preset notch interference detection threshold value to obtain a notch processed frequency spectrum; the method specifically comprises the following steps: performing notch processing on the initial frequency spectrum based on a preset first notch interference detection threshold value, calculating a first notch interference detection threshold value, performing first notch processing on the initial frequency spectrum based on the first notch interference detection threshold value, and obtaining a first frequency spectrum of an echo signal after the first notch processing; performing notch processing on the first frequency spectrum based on a preset second notch interference detection threshold value, calculating a second notch interference detection threshold value, and performing secondary notch processing on the first frequency spectrum based on the second notch interference detection threshold value to obtain a frequency spectrum subjected to secondary notch processing;

filtering the frequency spectrum subjected to notch processing to obtain a filtered frequency spectrum;

performing spectrum extrapolation processing on the filtered spectrum based on a preset prediction model to obtain forward extrapolation spectrum data and backward extrapolation spectrum data;

reconstructing the forward extrapolated spectrum data, the backward extrapolated spectrum data and the filtered spectrum to obtain a target spectrum without loss;

and recovering the frequency modulation information of the distance direction signal based on the target frequency spectrum without deletion to obtain a target echo signal which inhibits interference and has a complete frequency spectrum.

2. The method according to claim 1, wherein the performing reconstruction processing based on the forward-extrapolated spectrum data, the backward-extrapolated spectrum data, and the filtered spectrum to obtain a target spectrum without loss specifically includes:

carrying out missing spectrum reconstruction based on the forward extrapolated spectrum and the backward extrapolated spectrum to obtain a missing spectrum;

and splicing the filtered frequency spectrum and the missing frequency spectrum to obtain the target frequency spectrum without missing.

3. The method of claim 1, wherein the predictive model comprises an AR linear predictive model; the method further comprises the step of constructing the AR linear prediction model, and the method specifically comprises the following steps:

determining the order of the AR linear prediction model based on the number of the distance direction sampling points;

calculating coefficients of the AR linear prediction model based on a preset calculation method;

and constructing the AR linear prediction model based on the order and the coefficient.

4. The method of claim 3, wherein the predetermined calculation method comprises one or more of: berger's algorithm and improved covariance algorithm.

5. A radio frequency interference suppression device for SAR echo signals, comprising:

the transformation module is used for carrying out distance Fourier transformation on the received initial echo signal to obtain an initial frequency spectrum corresponding to the initial echo signal;

the notch processing module is used for carrying out notch processing on the initial frequency spectrum based on a preset notch interference detection threshold value to obtain a frequency spectrum after notch processing; the notching processing module is specifically configured to: performing notch processing on the initial frequency spectrum based on a preset first notch interference detection threshold value, calculating a first notch interference detection threshold value, performing first notch processing on the initial frequency spectrum based on the first notch interference detection threshold value, and obtaining a first frequency spectrum of an echo signal after the first notch processing; performing notch processing on the first frequency spectrum based on a preset second notch interference detection threshold value, calculating a second notch interference detection threshold value, and performing second notch processing on the first frequency spectrum based on the second notch interference detection threshold value to obtain a frequency spectrum subjected to secondary notch processing;

the filtering processing module is used for filtering the frequency spectrum subjected to the notch processing to obtain a filtered frequency spectrum;

the spectrum extrapolation processing module is used for carrying out spectrum extrapolation processing on the filtered spectrum based on a preset prediction model to obtain forward extrapolation spectrum data and backward extrapolation spectrum data;

a reconstruction module, configured to perform reconstruction processing based on the forward extrapolated spectrum data, the backward extrapolated spectrum data, and the filtered spectrum, to obtain a target spectrum without loss;

and the recovery module is used for recovering the frequency modulation information of the distance direction signal based on the target frequency spectrum without loss to obtain a target echo signal which inhibits interference and has a complete frequency spectrum.

6. The apparatus of claim 5, wherein the reconstruction module is specifically configured to:

carrying out missing spectrum reconstruction based on the forward extrapolation frequency spectrum and the backward extrapolation frequency spectrum to obtain a missing spectrum;

and splicing the filtered frequency spectrum and the missing frequency spectrum to obtain the target frequency spectrum without missing.

7. The apparatus of claim 5, wherein the predictive model comprises an AR linear predictive model; the apparatus further comprises a building module for building the AR linear prediction model, the building module being specifically configured to:

determining the order of the AR linear prediction model based on the number of the distance direction sampling points;

calculating coefficients of the AR linear prediction model based on a preset calculation method;

and constructing the AR linear prediction model based on the order and the coefficient.

8. An imaging method, comprising the steps of:

obtaining corresponding two-dimensional SAR data based on a target echo signal obtained by the method of any of claims 1-4;

and imaging the target object by using the two-dimensional SAR data.

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