CN113176543B - Radio frequency interference suppression method and system based on multi-dimensional information combination - Google Patents
Radio frequency interference suppression method and system based on multi-dimensional information combination Download PDFInfo
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Abstract
The invention provides a radio frequency interference suppression method and a system with multi-dimensional information combination, which comprises the following steps: step 1: modeling analysis is carried out on the existing P wave band potential interference to obtain an analysis result; step 2: according to the analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained; and step 3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference; and 4, step 4: the pulse type radio frequency interference signal is segmented on a time domain, converted into continuous radio frequency interference for processing, and the processed segments are spliced to obtain an echo signal after interference suppression. The invention provides a radio frequency interference suppression system combining multidimensional domains, which reduces the loss of useful echo signals and improves the robustness of the performance of a radio frequency interference suppression algorithm of a P-band SAR system.
Description
Technical Field
The invention relates to the technical field of radio frequency interference suppression, in particular to a radio frequency interference suppression method and system based on multi-dimensional information combination.
Background
The P-waveband SAR satellite has the advantages of all-time, all-weather and large-range earth observation of the satellite-borne SAR and strong penetrating capability of the P-waveband radar to leaf clusters and shallow earth surfaces. The global biomass, the high-precision ionized layer TEC data, the soil humidity, glacier monitoring and other data are effectively obtained, so that the sensing and detecting capabilities of human beings on the surrounding living environment are greatly enriched and improved; as a space-based system with global environment monitoring capability, the system is an indispensable important component for future development of national civil satellites. However, the SAR working in the P band is easily interfered by electromagnetic signals of other civil radio devices such as a television network and a communication network in the same band, which seriously affects the imaging quality of the SAR system, and further brings difficulties to subsequent SAR target detection, tracking and identification processing, and radio frequency interference suppression is one of key technologies for developing P band satellites.
Most of the existing researches and inventions adopt an interference suppression processing method aiming at a single change domain based on characteristic values, oblique projection filtering, space-frequency cascade filtering, compressed sensing and the like, such as patent document CN103675768A (application number: CN201310693687.7), patent document CN106501781A (application number: CN201610965930.X), patent document CN106646472A (application number: CN201611260024.6) and the like, and aiming at the diversity and complexity of the interference signals of the spaceborne P-band SAR, the interference signals are highly overlapped in a time domain, a frequency domain and a time-frequency domain, and the overlapping degree in a statistical information domain (characteristic subspace) is also high, wherein the difficulty of processing is further increased by a side lobe characteristic brought by pulse type radio frequency interference, so that the existing interference suppression processing algorithm aiming at the single change domain (such as a Notch frequency domain trap method, a characteristic subspace method, an STFT and a WT method and the like) fails.
Disclosure of Invention
In view of the defects in the prior art, the present invention aims to provide a method and a system for radio frequency interference suppression with multi-dimensional information combination.
The radio frequency interference suppression method based on multi-dimensional information combination provided by the invention comprises the following steps:
step 1: aiming at the problem of model mismatch of the existing radio frequency interference suppression algorithm, modeling analysis is carried out on the existing P-band potential interference to obtain an analysis result;
step 2: according to the potential interference modeling analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained;
and 3, step 3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference;
and 4, step 4: according to the characteristic that the pulse type radio frequency interference signal shows pulse type discontinuity in the time domain, the pulse type radio frequency interference signal is segmented in the time domain, the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed, interference suppression processing is carried out on the interference after the segmentation processing by combining the characteristic domain dimension, the processed segments are spliced, and an echo signal after the interference suppression is obtained.
Preferably, in the step 1, a modeling analysis is performed on potential interferences, where the interferences include:
pulsed radio frequency interference: windowing is performed in the time domain based on continuous radio frequency interference, and the formula is as follows:
ip(n)＝i(n)×w(n)，n＝1，2，...
wherein i (n) is the original signal, w (n) is the window function;
wherein, N0Is the window start time, M represents the window duration, N0+ M represents the end time of the window; thus, the expression of pulsed radio frequency interference is:
wherein, L is the number of frequency modulation interference; l is the number of sequences;
narrowband radio frequency interference: for narrowband NBI interference in the form of chirp signals, the modeling is:
in the formula (f)lIs the l carrier frequency, Al(n) is the l-th amplitude, glIn order to adjust the frequency, L is the number of frequency-adjusting interference;
continuous radio frequency interference: continuous radio frequency interference in a P band comprises fixed/mobile communication, and wireless communication services are arranged in each region in the frequency band;
due to the nature of radio frequency interference, it is modeled as a superposition of multiple sinusoids with sampling periods, as follows:
wherein L is the frequency, al(n) denotes amplitude, n denotes time-varying property, flIs an unknown frequency.
Preferably, the potential interference modeling analysis result obtained in step 2 is used to obtain the characteristics of continuous radio frequency interference, narrow band radio frequency interference and pulse radio frequency interference, and the principle is as follows:
the power of the continuous radio frequency interference ratio SAR echo signal is high, and the continuous radio frequency interference ratio SAR echo signal is not easy to distinguish in a time domain; after the frequency domain is converted, the amplitude of the interfered frequency point is higher than that of the frequency point which is not interfered; the frequency spectrum of an echo signal of the narrow-band radio frequency interference on a frequency domain is flat, and the narrow-band interference is in a peak shape; the frequency of the time-frequency spectrum narrow-band radio frequency interference is fixed, and the whole echo pulse is continued; the impulse radio frequency interference is highly overlapped in time domain, frequency domain and time-frequency domain, so that the existing interference suppression processing algorithm aiming at a single change domain is invalid.
Preferably, the principle of combining the time-frequency domain dimension and the prior information to suppress the narrowband radio frequency interference in step 3 is as follows:
the specific form of the transmitted signal is known as an LFM signal, the prior information is utilized to assist in improving the performance of an SAR system interference suppression algorithm, and interference is suppressed by means of a spread spectrum communication principle;
processing in a time-frequency domain dimension to suppress signals: performing wavelet transformation on a signal spectrum at the time of receiving the interference on a time-frequency plane, and inhibiting radio frequency interference in a wavelet domain; when the interference is filtered on a time-frequency plane by utilizing wavelet transformation, a short-time Fourier spectrum at the moment of receiving the interference is firstly transformed into a wavelet domain, and then a wavelet coefficient corresponding to the radio frequency interference is detected and the interference coefficient is filtered through a preset filter.
Preferably, the principle of suppressing the pulsed radio frequency interference in the step 4 with respect to the combined time domain dimension and the characteristic domain dimension is as follows:
the method comprises the steps that pulse type radio frequency interference signals are segmented in a time domain by utilizing the characteristic that the pulse type radio frequency interference signals appear in a pulse type discontinuous mode in the time domain, and the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed; performing interference suppression processing on the segmented interference by combining the characteristic domain dimensions, and splicing the processed segments to obtain echo signals after interference suppression;
the SAR echo signal of the radio frequency interference is expressed by the formula:
X＝S+I+N
wherein S represents a useful signal, I represents narrow-band interference, and N represents a noise signal;
regarding each segmented echo data, targets of different distance units are regarded as scattering point models, each scattering point has independent and same-distribution statistical characteristics, M distance samples are obtained in each echo of SAR data to be processed, X is a value of a certain distance sample, time sliding vector recording with a fixed length of L is carried out on the data of the M distance samples of each echo, the data are arranged into a matrix, and a data matrix of Lx (M-L +1) is obtained
The expression is as follows:
order to
In the kth column of the data matrix, then
The expression is as follows:
the biased autocorrelation matrix expression is thus obtained as follows:
will be provided with
Performing characteristic decomposition, arranging the obtained characteristic values in a size order to form lambda1＞λ2＞...＞λLThe corresponding feature vector is U1，U2，...ULA space constructed by the feature vectors corresponding to the feature values is called an interference subspace, and the expression is as follows:
r represents a characteristic value serial number;
narrow-band interference suppression of characteristic subspace filtering is carried out on recorded echo data, interference in the data is filtered out, and the interference is a data matrix
Each vector in (1)
To the direction of
Spatial projection component, the expression is:
the echo data after the interference is removed is as follows:
obtaining the echo data after removing the interference after each segmentation data according to the method, and then reversely constructing the original echo data according to the rule and the sequence of the segmentation in the time domain in the step 4.1 to obtain the whole echo data after removing the interference.
The multi-dimensional information combined radio frequency interference suppression system provided by the invention comprises:
module M1: aiming at the problem of model mismatch of the existing radio frequency interference suppression algorithm, modeling analysis is carried out on the existing P-band potential interference to obtain an analysis result;
module M2: according to the potential interference modeling analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained;
module M3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference;
module M4: according to the characteristic that the pulse type radio frequency interference signal presents pulse type discontinuity in the time domain, the pulse type radio frequency interference signal is segmented in the time domain, the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed, interference suppression processing is carried out on the interference after the segmentation processing in combination with the characteristic domain dimension, the processed segments are spliced, and an echo signal after the interference suppression is obtained.
Preferably, in the module M1, a model analysis is performed on potential interferences, including:
pulsed radio frequency interference: windowing is performed in the time domain based on continuous radio frequency interference, and the formula is as follows:
ip(n)＝i(n)×w(n)，n＝1，2，..
wherein i (n) is the original signal, w (n) is the window function;
wherein N is0Is the window start time, M represents the window duration, N0+ M represents the window ending time; thus, pulsed radio frequency interferenceThe expression is as follows:
wherein, L is the number of frequency modulation interference; l is the number of sequences;
narrowband radio frequency interference: for narrowband NBI interference in the form of chirp signals, the modeling is:
in the formula (f)lIs the l carrier frequency, Al(n) is the l-th amplitude, glIn order to adjust the frequency, L is the number of frequency-adjusting interference;
continuous radio frequency interference: continuous radio frequency interference in a P band comprises fixed/mobile communication, and wireless communication services are arranged in each region in the frequency band;
due to the nature of radio frequency interference, it is modeled as a superposition of multiple sinusoids with sampling periods, as follows:
wherein L is the frequency, al(n) denotes amplitude, n denotes time-varying properties, flIs an unknown frequency.
Preferably, the module M2 obtains a potential interference modeling analysis result, and obtains characteristics of continuous radio frequency interference, narrow band radio frequency interference, and pulsed radio frequency interference, according to the following principle:
the continuous radio frequency interference ratio SAR echo signal has high power and is not easy to distinguish in a time domain; after the frequency domain is converted, the amplitude of the interfered frequency point is higher than that of the frequency point which is not interfered; the frequency spectrum of an echo signal of the narrow-band radio frequency interference on a frequency domain is flat, and the narrow-band interference is in a peak shape; the frequency of the time-frequency spectrum narrow-band radio frequency interference is fixed, and the whole echo pulse is continued; the impulse radio frequency interference is highly overlapped in a time domain, a frequency domain and a time-frequency domain, so that the existing interference suppression processing algorithm aiming at a single change domain is invalid.
Preferably, the principle of combining the time-frequency domain dimension and the prior information to suppress the narrowband radio frequency interference in the module M3 is as follows:
the specific form of the transmitted signal is known as an LFM signal, the prior information is utilized to assist in improving the performance of an SAR system interference suppression algorithm, and interference is suppressed by means of a spread spectrum communication principle;
processing in a time-frequency domain dimension to suppress signals: performing wavelet transformation on a signal frequency spectrum at the moment of receiving interference on a time-frequency plane, and inhibiting radio frequency interference in a wavelet domain; when the interference is filtered on a time-frequency plane by utilizing wavelet transformation, a short-time Fourier spectrum at the moment of receiving the interference is firstly transformed into a wavelet domain, and then a wavelet coefficient corresponding to the radio frequency interference is detected and the interference coefficient is filtered through a preset filter.
Preferably, the principle of suppressing the pulsed radio frequency interference in the module M4 with respect to the joint time domain dimension and the characteristic domain dimension is as follows:
the method comprises the steps that pulse type radio frequency interference signals are segmented in a time domain by utilizing the characteristic that the pulse type radio frequency interference signals appear in a pulse type discontinuous mode in the time domain, and the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed; performing interference suppression processing on the segmented interference by combining the characteristic domain dimensions, and splicing the processed segments to obtain echo signals after interference suppression;
the SAR echo signal of the radio frequency interference is represented by the formula:
X＝S+I+N
wherein S represents a useful signal, I represents narrow-band interference, and N represents a noise signal;
regarding targets with different distance units as scattering point models for each segmented echo data, wherein each scattering point has independent and equally distributed statistical featuresThe SAR data to be processed has M distance samples in each echo, X is the value of a certain distance sample, the data of the M distance samples of each echo is recorded by a time sliding vector with the fixed length of L and is arranged into a matrix to obtain a data matrix of Lx (M-L +1)
The expression is as follows:
order to
In the kth column of the data matrix, then
The expression is as follows:
the biased autocorrelation matrix expression is thus obtained as follows:
will be provided with
Performing characteristic decomposition, arranging the obtained characteristic values in a size order to form lambda1＞λ2＞...＞λLThe corresponding feature vector is U1，U2，...ULA space constructed by the feature vectors corresponding to the feature values is called an interference subspace, and the expression is as follows:
r is represented as a characteristic value serial number;
narrow-band interference suppression of characteristic subspace filtering is carried out on recorded echo data, interference in the data is filtered out, and the interference is a data matrix
Each vector in (1)
To the direction of
Spatial projection component, the expression is:
the echo data after the interference is removed is as follows:
and obtaining the echo data after the interference is removed after each segmentation data is obtained according to the method, and then reversely constructing the original echo data according to the rule and the sequence of the module M4.1 in the time domain segmentation to obtain the whole echo data after the interference is removed.
Compared with the prior art, the invention has the following beneficial effects:
the invention starts from the angle of multi-transform domain (including time-frequency domain, wavelet domain, characteristic domain and the like) and multi-information (statistical characteristic, geometric characteristic, textural characteristic and the like) combination, and excavates inherent prior information and characteristics of a P-band SAR system by further excavating the characteristics of interference signals in the multi-dimensional domain, and provides a novel prior information-assisted radio frequency interference suppression device combining the multi-dimensional domain (such as time domain, time-frequency domain, characteristic subspace domain and the like), thereby reducing the loss of useful echo signals and improving the robustness of the performance of a radio frequency interference suppression algorithm of the P-band SAR system.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a diagram of a time domain characteristic of pulsed RF interference;
FIG. 2 is a diagram of frequency domain characteristics of pulsed RF interference;
FIG. 3 is a time-frequency domain plot of the pulsed RF interference;
FIG. 4 is a diagram of characteristics of a characteristic domain of pulsed RF interference;
FIG. 5 is a schematic diagram of RF interference suppression with multi-transform domain and multi-dimensional information combination according to the present invention;
fig. 6 is a schematic diagram of the whole interference suppression system;
fig. 7 is a final result diagram of the multi-dimensional information-combined rfic suppression apparatus according to the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
Example (b):
the invention provides a priori information assisted multi-transform domain and multi-dimensional information combined radio frequency interference suppression method by exploring and utilizing some inherent priori information of a P-band SAR system and excavating inherent difference and sparse characteristics of a radio frequency interference signal and an SAR echo signal in a transform domain, thereby improving the problems of bright lines and image blurring in an SAR image and improving the imaging quality of the SAR system, and the method comprises the following steps:
and 2, obtaining the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference according to the potential interference modeling analysis result in the step 1. The pulse radio frequency interference is found to be highly overlapped in a time domain, a frequency domain and a time-frequency domain, and the overlapping degree in a statistical information domain (a feature subspace) is also high, wherein the side lobe feature brought by the pulse radio frequency interference further increases the processing difficulty, so that the existing interference suppression processing algorithm (such as a Notch frequency domain Notch method, a feature subspace method, an STFT (standard time Fourier transform) and a WT (WT transform) method and the like) aiming at a single change domain fails;
and 3, processing by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference. According to the specific form of the interference emission signal, which is known as an LFM signal, the prior information is utilized to assist in improving the performance of the SAR system interference suppression algorithm. Simultaneously, combining the time-frequency domain dimension information, and processing the interference in the time-frequency domain;
and 4, processing the pulse type radio frequency interference by combining the time domain dimension and the characteristic domain dimension. The pulse radio frequency interference signal is segmented in the time domain by utilizing the characteristic that the pulse radio frequency interference signal appears in the time domain in a pulse discontinuous way, so that the pulse radio frequency interference is converted into continuous radio frequency interference for processing; and then, carrying out interference suppression processing on the interference subjected to the segmentation processing by combining the characteristic domain dimensions, and splicing the processed segments to obtain an echo signal subjected to interference suppression.
Before and after the interference suppression, some preprocessing is required, and the operation of the whole interference suppression device system is described below with reference to fig. 6:
firstly, each azimuth pulse signal is converted into a distance frequency domain to finish radio frequency interference identification; if the radio frequency interference exists, modeling and analyzing potential radio frequency interference sources of the SAR system; on the basis, the suppression of the radio frequency interference is completed, and the influence of the suppression on the SAR imaging quality is analyzed. In order to better evaluate the performance of the proposed radio frequency interference suppression algorithm, an effective radio frequency interference suppression algorithm performance evaluation mechanism needs to be researched, and the correctness of model establishment and the effectiveness of the evaluation mechanism are verified through a simulation experiment, so that a foundation is laid for the subsequent actual measurement SAR data processing. The scheme is mainly used for solving the problems of model mismatch, useful signal loss, high calculation complexity and the like of the existing radio frequency interference suppression method, and the problems of high overlapping of time domain, frequency domain and time-frequency domain of pulse radio frequency interference signals and high overlapping degree of statistical information domain (characteristic subspace). Based on the problems, the difference and the sparse characteristics of the radio frequency interference signal and the SAR echo signal in a transform domain are mined by exploring some inherent prior information and characteristics of the SAR system, and the radio frequency interference suppression algorithm of the SAR system is researched by jointly utilizing multi-dimensional information. Secondly, Doppler parameter estimation, motion compensation and azimuth compression are carried out on the echo signals after radio frequency interference suppression is finished to obtain an SAR image, multi-view processing is carried out on the SAR image to suppress speckle noise, the SAR image with good focus is obtained, and data support is provided for subsequent target identification, moving target detection and tracking.
The invention uses the interference suppression method of the combined multidimensional domain (such as time domain, time-frequency domain, characteristic subspace domain, etc.), the concrete steps are as follows:
the purpose of utilizing information such as multiple transform domains and multiple dimensions to realize interference suppression is to mine the fine information difference of SAR echo signals and interference signals in different transform domains and multiple transform domains, so as to extract different characteristics. And exploring some intrinsic characteristics (such as intrinsic texture characteristics, statistical information characteristics, geometric information characteristics and the like) of the interference signal and the SAR echo signal in other dimensions, and effectively suppressing the interference and simultaneously minimizing the loss of a useful echo signal by using the multi-dimensional information in a combined manner.
In steps 3 and 4 of the invention, an interference suppression method combining multidimensional domains (such as time domain, time-frequency domain, characteristic subspace domain and the like) is provided, and the purpose of interference suppression is achieved by utilizing and excavating inherent prior information and characteristics of a P-waveband SAR system. This method has a moderate computational complexity. And a multi-index combined algorithm interference suppression performance evaluation mechanism is researched. Through simulation experiments, the processing effect is good in the frequency domain, although a small part of useful echo signals are lost, the interference signals are suppressed on the whole, and meanwhile, the subsequent imaging is not influenced by the lost signals. Fig. 7 is a graph showing the results of the combined multidimensional domain interference suppression method.
The multi-dimensional information combined radio frequency interference suppression system provided by the invention comprises:
module M1: aiming at the problem of model mismatch of the existing radio frequency interference suppression algorithm, modeling analysis is carried out on the existing P-band potential interference to obtain an analysis result;
module M2: according to the potential interference modeling analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained;
module M3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference;
module M4: according to the characteristic that the pulse type radio frequency interference signal shows pulse type discontinuity in the time domain, the pulse type radio frequency interference signal is segmented in the time domain, the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed, interference suppression processing is carried out on the interference after the segmentation processing by combining the characteristic domain dimension, the processed segments are spliced, and an echo signal after the interference suppression is obtained.
The module M1 models potential interferences including:
pulsed radio frequency interference: based on continuous radio frequency interference, windowing is performed on a time domain, and the formula is as follows:
ip(n)＝i(n)×w(n)，n＝1，2，...
wherein i (n) is the original signal, w (nn) is the window function;
wherein N is0Is the window start time, M represents the window duration, N0+ M represents the end time of the window; thus, the expression of pulsed radio frequency interference is:
wherein, L is the number of frequency modulation interference; l is the number of sequences;
narrowband radio frequency interference: for narrowband NBI interference in the form of chirp signals, the modeling is:
in the formula, flIs the l carrier frequency, Al(n) is the l-th amplitude, glIn order to adjust the frequency, L is the number of frequency-adjusting interference;
continuous radio frequency interference: continuous radio frequency interference in the P band comprises fixed/mobile communication, and wireless communication services are arranged in each region in the frequency band;
due to the nature of radio frequency interference, it is modeled as a superposition of multiple sinusoids with sampling periods, as follows:
wherein L is the frequency, al(n) denotes amplitude, n denotes time-varying property, flIs an unknown frequency.
The module M2 obtains a potential interference modeling analysis result, and obtains the characteristics of continuous radio frequency interference, narrow band radio frequency interference, and pulsed radio frequency interference, the principle is as follows: the continuous radio frequency interference ratio SAR echo signal has high power and is not easy to distinguish in a time domain; after the frequency domain is converted, the amplitude of the interfered frequency point is higher than that of the frequency point which is not interfered; the frequency spectrum of an echo signal of the narrow-band radio frequency interference on a frequency domain is flat, and the narrow-band interference is in a peak shape; the frequency of the time-frequency spectrum narrow-band radio frequency interference is fixed, and the whole echo pulse is continued; the impulse radio frequency interference is highly overlapped in the time domain, the frequency domain, and the time-frequency domain, so that the existing interference suppression processing algorithm for a single change domain is invalid, as shown in fig. 1 to 4, which are characteristic diagrams of the impulse radio frequency interference in the time domain, the frequency domain, the time-frequency domain, and the characteristic domain.
The principle of combining the time-frequency domain dimension and the prior information to suppress the narrowband radio frequency interference in the module M3 is as follows: the specific form of the transmitted signal is known as an LFM signal, the prior information is utilized to assist in improving the performance of an SAR system interference suppression algorithm, and interference is suppressed by means of a spread spectrum communication principle; processing in a time-frequency domain dimension to suppress signals: performing wavelet transformation on a signal spectrum at the time of receiving the interference on a time-frequency plane, and inhibiting radio frequency interference in a wavelet domain; when the interference is filtered on a time-frequency plane by utilizing wavelet transformation, a short-time Fourier spectrum at the moment of receiving the interference is firstly transformed into a wavelet domain, and then a wavelet coefficient corresponding to the radio frequency interference is detected and the interference coefficient is filtered through a preset filter.
As shown in fig. 5, the principle of suppressing the pulsed radio frequency interference in the module M4 for the joint time domain dimension and the characteristic domain dimension is as follows: the method comprises the steps that pulse type radio frequency interference signals are segmented in a time domain by utilizing the characteristic that the pulse type radio frequency interference signals appear in a pulse type discontinuous mode in the time domain, and the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed; performing interference suppression processing on the segmented interference by combining the characteristic domain dimensions, and splicing the processed segments to obtain echo signals after interference suppression;
the SAR echo signal of the radio frequency interference is represented by the formula:
X＝S+I+N
wherein S represents a useful signal, I represents narrow-band interference, and N represents a noise signal;
regarding each segmented echo data, targets of different distance units are regarded as scattering point models, each scattering point has independent and same-distribution statistical characteristics, M distance samples are obtained in each echo of SAR data to be processed, X is a value of a certain distance sample, time sliding vector recording with a fixed length of L is carried out on the data of the M distance samples of each echo, the data are arranged into a matrix, and a data matrix of Lx (M-L +1) is obtained
The expression is as follows:
order to
In the kth column of the data matrix, then
The expression is as follows:
the biased autocorrelation matrix expression is thus obtained as follows:
will be provided with
Performing characteristic decomposition, arranging the obtained characteristic values in a size order to form lambda1＞λ2＞...＞λLThe corresponding feature vector is U1，U2，...ULA space constructed by the feature vectors corresponding to the feature values is called an interference subspace, and the expression is as follows:
r is represented as a characteristic value serial number;
narrow-band interference suppression of characteristic subspace filtering is carried out on recorded echo data, interference in the data is filtered out, and the interference is a data matrix
Each vector in (1)
To the direction of
Spatial projection component, the expression is:
the echo data after the interference is removed is as follows:
and obtaining the echo data after the interference is removed after each segmentation data is obtained according to the method, and then reversely constructing the original echo data according to the rule and the sequence of the module M4.1 in the time domain segmentation to obtain the whole echo data after the interference is removed.
Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (8)
1. A radio frequency interference suppression method based on multi-dimensional information combination is characterized by comprising the following steps:
step 1: aiming at the problem of model mismatch of the existing radio frequency interference suppression algorithm, modeling analysis is carried out on the existing P-band potential interference to obtain an analysis result;
step 2: according to the potential interference modeling analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained;
and step 3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference;
and 4, step 4: according to the characteristic that the pulse type radio frequency interference signal presents pulse type discontinuity in the time domain, the pulse type radio frequency interference signal is segmented in the time domain, the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed, interference suppression processing is carried out on the interference after the segmentation processing by combining the dimensions of the characteristic domain, the processed segments are spliced, and an echo signal after the interference suppression is obtained;
in the step 1, a modeling analysis is performed on potential interference, where the interference includes:
pulsed radio frequency interference: based on continuous radio frequency interference, windowing is performed on a time domain, and the formula is as follows:
ip(n)＝i(n)×w(n),n＝1,2,...
wherein i (n) is the original signal, w (n) is the window function;
wherein N is0Is the window start time, M represents the window duration, N0+ M represents the window ending time; thus, the expression of pulsed radio frequency interference is:
wherein, L is the number of frequency modulation interference; l is the number of sequences;
narrowband radio frequency interference: for narrowband NBI interference in the form of chirp signals, the modeling is:
in the formula (f)lIs the l carrier frequency, Al(n) is the l-th amplitude, glIn order to adjust the frequency, L is the number of frequency-adjusting interference;
continuous radio frequency interference: continuous radio frequency interference in a P band comprises fixed/mobile communication, and wireless communication services are arranged in each region in the frequency band;
due to the nature of radio frequency interference, it is modeled as a superposition of multiple sinusoids with sampling periods, as follows:
wherein L is the frequency, al(n) denotes amplitude, n denotes time-varying property, flIs an unknown frequency.
2. The multi-dimensional information-based radio frequency interference suppression method according to claim 1, wherein the potential interference modeling analysis result obtained in step 2 is used to obtain the characteristics of continuous radio frequency interference, narrowband radio frequency interference and pulsed radio frequency interference, and the principle is as follows:
the continuous radio frequency interference ratio SAR echo signal has high power and is not easy to distinguish in a time domain; after the frequency domain is converted, the amplitude of the interfered frequency point is higher than that of the frequency point which is not interfered; the frequency spectrum of an echo signal of the narrow-band radio frequency interference on a frequency domain is flat, and the narrow-band interference is in a peak shape; the frequency of the time-frequency spectrum narrow-band radio frequency interference is fixed, and the whole echo pulse is continued; the impulse radio frequency interference is highly overlapped in time domain, frequency domain and time-frequency domain, so that the existing interference suppression processing algorithm aiming at a single change domain is invalid.
3. The method for suppressing multi-dimensional information combined radio frequency interference according to claim 1, wherein the principle of suppressing the combined time-frequency domain dimension and the prior information for the narrowband radio frequency interference in the step 3 is as follows:
the specific form of the transmitted signal is known as an LFM signal, the prior information is utilized to assist in improving the performance of an SAR system interference suppression algorithm, and interference is suppressed by means of a spread spectrum communication principle;
processing in a time-frequency domain dimension to suppress signals: performing wavelet transformation on a signal spectrum at the time of receiving the interference on a time-frequency plane, and inhibiting radio frequency interference in a wavelet domain; when the interference is filtered on a time-frequency plane by utilizing wavelet transformation, a short-time Fourier spectrum at the moment of receiving the interference is firstly transformed into a wavelet domain, and then a wavelet coefficient corresponding to the radio frequency interference is detected and the interference coefficient is filtered through a preset filter.
4. The method for suppressing multi-dimensional information combination according to claim 1, wherein the principle of suppressing the pulsed radio frequency interference combination time domain dimension and the characteristic domain dimension in step 4 is as follows:
the method comprises the steps that pulse radio frequency interference signals are segmented in a time domain by utilizing the characteristic that the pulse radio frequency interference signals appear in a pulse discontinuous mode in the time domain, and the pulse radio frequency interference is converted into continuous radio frequency interference for processing; performing interference suppression processing on the segmented interference by combining the characteristic domain dimensions, and splicing the processed segments to obtain echo signals after interference suppression;
the SAR echo signal of the radio frequency interference is represented by the formula:
X＝S+I+N
wherein S represents a useful signal, I represents narrow-band interference, and N represents a noise signal;
regarding each segmented echo data, targets of different distance units are regarded as scattering point models, each scattering point has independent and same-distribution statistical characteristics, M distance samples are obtained in each echo of SAR data to be processed, X is a value of a certain distance sample, time sliding vector recording with a fixed length of L is carried out on the data of the M distance samples of each echo, the data are arranged into a matrix, and a data matrix of Lx (M-L +1) is obtained
The expression is as follows:
order to
In the kth column of the data matrix, then
The expression is as follows:
the biased autocorrelation matrix expression is thus obtained as follows:
will be provided with
Performing characteristic decomposition, arranging the obtained characteristic values in a size order to form lambda1＞λ2＞…＞λLThe corresponding feature vector is U1,U2,…ULA space constructed by the feature vectors corresponding to the feature values is called an interference subspace, and the expression is as follows:
narrow-band interference suppression of characteristic subspace filtering is carried out on recorded echo data, interference in the data is filtered out, and the interference is a data matrix
Each vector in (1)
To the direction of
Spatial projection component, the expression is:
the echo data after the interference is removed is as follows:
obtaining the echo data after removing the interference after each segmentation data according to the method, and then reversely constructing the original echo data according to the rule and the sequence of the segmentation in the time domain in the step 4.1 to obtain the whole echo data after removing the interference.
5. A multi-dimensional information combined radio frequency interference suppression system is characterized by comprising:
module M1: aiming at the problem of model mismatch of the existing radio frequency interference suppression algorithm, modeling analysis is carried out on the existing P-band potential interference to obtain an analysis result;
module M2: according to the potential interference modeling analysis result, the characteristics of continuous radio frequency interference, narrow-band radio frequency interference and pulse radio frequency interference are obtained;
module M3: processing is carried out by combining the time-frequency domain dimension and the prior information aiming at the narrow-band radio frequency interference;
module M4: according to the characteristic that the pulse type radio frequency interference signal presents pulse type discontinuity in the time domain, the pulse type radio frequency interference signal is segmented in the time domain, the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed, interference suppression processing is carried out on the interference after the segmentation processing by combining the dimensions of the characteristic domain, the processed segments are spliced, and an echo signal after the interference suppression is obtained;
the module M1 models potential interferences including:
pulsed radio frequency interference: windowing is performed in the time domain based on continuous radio frequency interference, and the formula is as follows:
ip(n)＝i(n)×w(n),n＝1,2,...
wherein i (n) is the original signal, w (n) is the window function;
wherein N is0Is the window start time, M represents the window duration, N0+ M represents the end time of the window; thus, the expression of pulsed radio frequency interference is:
wherein, L is the number of frequency modulation interference; l is the number of sequences;
narrowband radio frequency interference: for narrowband NBI interference in the form of chirp signals, the modeling is:
in the formula (f)lIs the l carrier frequency, Al(n) is the l-th amplitude, glIn order to adjust the frequency, L is the number of frequency-adjusting interference;
continuous radio frequency interference: continuous radio frequency interference in a P band comprises fixed/mobile communication, and wireless communication services are arranged in each region in the frequency band;
due to the nature of radio frequency interference, it is modeled as a superposition of multiple sinusoids with sampling periods, as follows:
wherein L is frequency, al(n) denotes amplitude, n denotes time-varying property, flIs an unknown frequency.
6. The system according to claim 5, wherein the module M2 obtains the potential interference modeling analysis result to obtain the characteristics of continuous radio frequency interference, narrowband radio frequency interference, and pulsed radio frequency interference, according to the following principle:
the power of the continuous radio frequency interference ratio SAR echo signal is high, and the continuous radio frequency interference ratio SAR echo signal is not easy to distinguish in a time domain; after the frequency domain is converted, the amplitude of the interfered frequency point is higher than that of the frequency point which is not interfered; the frequency spectrum of an echo signal of the narrow-band radio frequency interference on a frequency domain is flat, and the narrow-band interference is in a peak shape; the frequency of the time-frequency spectrum narrow-band radio frequency interference is fixed, and the whole echo pulse is continued; the impulse radio frequency interference is highly overlapped in time domain, frequency domain and time-frequency domain, so that the existing interference suppression processing algorithm aiming at a single change domain is invalid.
7. The multi-dimensional information combined radio frequency interference suppression system according to claim 5, wherein the principle of combining the time-frequency domain dimension and the prior information for narrowband radio frequency interference in said module M3 is as follows:
the specific form of the transmitted signal is known as an LFM signal, the prior information is utilized to assist in improving the performance of an SAR system interference suppression algorithm, and interference is suppressed by means of a spread spectrum communication principle;
processing in a time-frequency domain dimension to suppress signals: performing wavelet transformation on a signal spectrum at the time of receiving the interference on a time-frequency plane, and inhibiting radio frequency interference in a wavelet domain; when the interference is filtered on a time-frequency plane by utilizing wavelet transformation, a short-time Fourier spectrum at the moment of receiving the interference is firstly transformed into a wavelet domain, and then a wavelet coefficient corresponding to the radio frequency interference is detected and the interference coefficient is filtered through a preset filter.
8. The system according to claim 5, wherein the principle of suppression for the pulsed rfi joint time domain dimension and the eigen domain dimension in the module M4 is as follows:
the method comprises the steps that pulse type radio frequency interference signals are segmented in a time domain by utilizing the characteristic that the pulse type radio frequency interference signals appear in a pulse type discontinuous mode in the time domain, and the pulse type radio frequency interference is converted into continuous type radio frequency interference to be processed; performing interference suppression processing on the segmented interference by combining the characteristic domain dimensions, and splicing the processed segments to obtain echo signals after interference suppression;
the SAR echo signal of the radio frequency interference is represented by the formula:
X＝S+I+N
wherein S represents a useful signal, I represents narrow-band interference, and N represents a noise signal;
for each of the segmented echo data sets,regarding targets of different distance units as scattering point models, wherein each scattering point has independent and uniformly distributed statistical characteristics, each echo of SAR data to be processed has M distance samples, X is a value of a certain distance sample, performing time sliding vector recording with fixed length of L on the data of the M distance samples of each echo, and arranging the data into a matrix to obtain a data matrix of Lx (M-L +1)
The expression is as follows:
order to
In the kth column of the data matrix, then
The expression is as follows:
the biased autocorrelation matrix expression is thus obtained as follows:
will be provided with
Performing characteristic decomposition, arranging the obtained characteristic values in a size order to form lambda1＞λ2＞…＞λLThe corresponding feature vector is U1,U2,…ULA space constructed by the characteristic vector corresponding to the characteristic value is called an interference subspace and an expressionThe method comprises the following steps:
narrow-band interference suppression of characteristic subspace filtering is carried out on recorded echo data, interference in the data is filtered out, and the interference is a data matrix
Each vector in (1)
To the direction of
Spatial projection component, the expression is:
the echo data after the interference is removed is as follows:
and obtaining the echo data after the interference is removed after each segmentation data is obtained according to the method, and then reversely constructing the original echo data according to the rule and the sequence of the module M4.1 in the time domain segmentation to obtain the whole echo data after the interference is removed.
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