CN115015849A - Interference suppression method and related device - Google Patents
Interference suppression method and related device Download PDFInfo
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Abstract
The invention provides an interference suppression method and a related device, and the interference suppression method comprises the following steps: processing an original echo signal to obtain a two-dimensional time-frequency graph corresponding to the original echo signal; detecting the two-dimensional time-frequency graph to obtain a broadband interference area; and reconstructing the broadband interference area to obtain a reconstructed echo signal. The method can effectively inhibit broadband interference.
Description
Technical Field
The present invention relates to the field of signal processing, and in particular, to an interference suppression method and related apparatus.
Background
Synthetic Aperture Radar (SAR) is a high resolution imaging Radar with excellent performance. Because of its ability to detect all-weather and large-range, it has been widely used in military field (strategic information detection, dynamic monitoring of war zone, target identification and tracking, etc.) and civil field (map mapping, ocean glacier detection, resource exploration, etc.). In recent years, with the increasing complexity of electromagnetic environment, radio frequency interference signals are inevitably mixed into the SAR echo signals, which has a serious influence on the SAR high-precision imaging and target detection capability. On one hand, the existence of radio frequency noise can reduce the SAR echo quality, so that the Doppler parameter estimation precision is reduced, and SAR image blurring and defocusing are caused; on the other hand, when high power radio frequency noise exists, the SAR image results may be severely corrupted, thereby losing a large amount of useful target information. Therefore, the research of an effective SAR interference suppression method for recovering the damaged SAR echo signal has important application value. Depending on the bandwidth of the interference signal, it can be divided into Narrow-Band interference (NBI) and Wide-Band interference (WBI). For NBI, the bandwidth only occupies a small part of the effective signal bandwidth, so that a better interference suppression effect can be obtained by a time domain or frequency domain analysis method, such as a frequency domain notch method, a subspace projection method, an empirical mode decomposition method and the like. For WBI, however, it is relatively complex to suppress WBI because it is highly overlapped with the desired target signal in both the time and frequency domains.
Disclosure of Invention
The application provides an interference suppression method and a related device, wherein the method can effectively suppress broadband interference.
In a first aspect, the present application provides an interference suppression method, including: determining the window length; processing the original echo signal by using a short-time Fourier transform method based on the window length to obtain a two-dimensional time-frequency graph; detecting the two-dimensional time-frequency graph to obtain a broadband interference area; and reconstructing the broadband interference area to obtain a reconstructed echo signal.
Wherein the window length is related to the frequency resolution and the time resolution of the two-dimensional time-frequency diagram.
Wherein the step of determining the window length comprises: processing the original echo signal by using a short-time Fourier transform method based on an initial standard deviation to obtain a first initial result, wherein the initial standard deviation is determined based on the sampling frequency of the original echo signal; calculating a first order differential result and a second order differential result of the first initial result; calculating a set of chirp rate estimate values for the original echo signal using the first order differential result and the second order differential result; and carrying out weighted average on the modulation frequency estimation values in the modulation frequency estimation value set, determining a prediction standard deviation based on the weighted average result, and determining the prediction standard deviation as the window length if the prediction standard deviation is smaller than a first threshold value.
The step of detecting the two-dimensional time-frequency diagram to obtain a broadband interference area comprises the following steps: determining a threshold value, wherein the threshold value is related to the precision of the broadband interference region; and detecting the two-dimensional time-frequency graph based on the threshold value by using a broadband detection algorithm to obtain a broadband interference area.
Wherein the step of determining the threshold value comprises: calculating by using the initial Rayleigh distribution parameter to obtain an initial threshold value; the initial Rayleigh distribution parameter is determined based on the two-dimensional time-frequency diagram; determining a time-frequency mask matrix based on the initial threshold value and the two-dimensional time-frequency graph, and determining a complementary time-frequency mask matrix based on the time-frequency mask matrix; determining a predicted Rayleigh distribution parameter based on the two-dimensional time-frequency graph and the complementary time-frequency mask matrix; and determining a final threshold value based on the predicted Rayleigh distribution parameter, wherein if the final threshold value is smaller than a second threshold value, the final threshold value is determined to be the threshold value.
The step of reconstructing the broadband interference region to obtain a reconstructed echo signal includes: determining a compression parameter; refining the time-frequency mask matrix by using the compression parameters to obtain a refined time-frequency mask matrix; and reconstructing the refined time-frequency mask matrix based on the compression parameters to obtain a reconstructed echo signal.
Wherein the step of determining the compression parameter comprises: defining a frequency resolution matrix and a time resolution matrix; the frequency resolution matrix comprises frequency resolution parameters corresponding to the two-dimensional time-frequency graph, and the time resolution matrix comprises time resolution parameters corresponding to the two-dimensional time-frequency graph; constructing a reference matrix based on the frequency resolution matrix and the time resolution matrix, wherein the size of the reference matrix is determined based on the size of the frequency resolution matrix and the size of the time resolution matrix; determining the compression parameter based on the reference matrix.
In a second aspect, the present application provides an interference suppression apparatus, comprising: a determining module for determining a window length; the processing module is used for processing the original echo signal by utilizing a short-time Fourier transform method based on the window length to obtain a two-dimensional time-frequency graph; the detection module is used for detecting the two-dimensional time-frequency diagram to obtain a broadband interference area; and the reconstruction module is used for reconstructing the broadband interference area to obtain a reconstructed echo signal.
In a third aspect, the present application provides an electronic device, including a processor and a memory coupled to each other, where the memory is configured to store program instructions for implementing any one of the methods described above; the processor is configured to execute the program instructions stored by the memory.
In a fourth aspect, the present application provides a computer readable storage medium storing a program file executable to implement the method of any one of the above.
The beneficial effects of the invention are different from the situation of the prior art, and the interference suppression method of the invention comprises the following steps: processing an original echo signal to obtain a two-dimensional time-frequency graph corresponding to the original echo signal; detecting the two-dimensional time-frequency graph to obtain a broadband interference area; and reconstructing the broadband interference region to obtain a reconstructed echo signal. The method can effectively inhibit broadband interference.
Drawings
Fig. 1 is a flowchart illustrating an interference suppression method according to a first embodiment of the present invention;
FIG. 2 is a flowchart illustrating an embodiment of a window length determination method;
FIG. 3 is a flowchart illustrating an embodiment of a threshold determination method;
FIG. 4 is a flowchart illustrating an embodiment of a compression parameter determination method;
fig. 5 is a schematic structural diagram of an interference suppression apparatus according to a first embodiment of the present invention;
FIG. 6 is a schematic structural diagram of an electronic device according to an embodiment of the invention;
FIG. 7 is a structural diagram of an embodiment of a computer-readable storage medium according to the invention.
Detailed Description
To further explain the technical means and effects of the present invention adopted to achieve the predetermined objects, the present invention will be described in detail with reference to the accompanying drawings and the detailed description. The foregoing and other technical matters, features and effects of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The drawings are only for reference and illustration purposes and are not intended to limit the technical aspects of the invention.
The invention aims to provide an SAR broadband interference suppression method based on high-precision time frequency representation, which is characterized in that on the basis of carrying out two-dimensional time frequency representation by adopting STFT (short-time Fourier Transform) with self-adaptive window width, a time frequency mask of WBI is constructed, a method of mask Second-order multiple synchronous compression Transform (MSST 2) is designed, high-resolution time frequency analysis is carried out on an echo, the time frequency mask is subjected to refining treatment, WBI is reconstructed at high precision, and SAR useful signals are recovered.
Referring to fig. 1, fig. 1 is a flowchart illustrating an interference suppression method according to a first embodiment of the present invention, which specifically includes:
step S11: the window length is determined.
Step S12: and processing the original echo signal by using a short-time Fourier transform method based on the window length to obtain a two-dimensional time-frequency graph.
Specifically, short-time fourier transform (STFT) with adaptive window width is performed on the original echo signal to obtain a corresponding two-dimensional time-frequency graph.
Fourier transforms and fast fourier transforms play an important role in signal processing. However, the fourier transform transforms the entire signal, and thus loses time information. While STFT, an extension of the fourier transform, provides time-frequency localization information of a signal and is widely used for time-frequency graph analysis, the basic idea of STFT is to perform a fourier transform on a portion of a signal, usually using a smoothing window for weighting.
For a discrete-time signal, the STFT may be expressed as:
wherein, the first and the second end of the pipe are connected with each other,
the number of the units of the imaginary number is expressed,
a time sample number is represented and,
which is indicative of the time delay,
a frequency sample number is indicated and,
the number of frequency sampling points is represented,
which represents a discrete-time signal that is,
a window function is represented.
In the present invention, the time-frequency plot generated by the STFT shows the time-frequency plot and the frequency spectrum of different types (chirp, sinusoidal chirp, am-fm) of WBI, the frequency spectrum being represented after normalization by Fast Fourier Transform (FFT) results.
A suitable window width is critical to obtain high resolution STFT results. When a long window is chosen, better frequency resolution is obtained, but time resolution is reduced. Therefore, a compromise between frequency resolution and time resolution is required. Therefore, in one embodiment, a window length is determined, and the window length is related to the frequency resolution and the time resolution of the two-dimensional time frequency graph; and processing the original echo signal by using a short-time Fourier transform method based on the window length to obtain the two-dimensional time-frequency graph.
Specifically, the gaussian window has the characteristic of minimum time-bandwidth product, and is widely used for time-frequency analysis. Gauss window
Is defined as:
wherein the content of the first and second substances,
in the form of a time, the time,
is the standard deviation and can be considered as a measure of the window length. Optimum value thereof
Comprises the following steps:
wherein the content of the first and second substances,
is the derivative of the instantaneous frequency, i.e. the instantaneous tuning frequency. But for
Accurate estimation of (d) is still a problem.
To determine
So as to obtain a time-frequency diagram with high aggregation degree, the invention designs the solution
step S21: and processing the original echo signal by using a short-time Fourier transform method based on an initial standard deviation to obtain a first initial result, wherein the initial standard deviation is determined based on the sampling frequency of the original echo signal.
Hypothesis signal
In that
The vicinity is approximately stationary, then the STFT result is now
Comprises the following steps:
wherein the content of the first and second substances,
and
are respectively signals at
The magnitude and frequency of the vicinity is,
in order to be a time delay,
is the frequency.
Order to
Available bandwidth
Empirically setting a sampling frequency of 0.02 times the bandwidth of the original echo signal to obtain an initial standard deviation
。
Processing the original echo signal based on the initial standard deviation by using a short-time Fourier transform method to obtain a first initial result, wherein the first initial result represents
。
Step S22: a first order differential result and a second order differential result of the first initial result are calculated.
Specifically, a first order differential result and a second order differential result of the first initial result are calculated, and the specific first order differential result is:
the second order differential results are:
wherein, the first and the second end of the pipe are connected with each other,
to take time
Multiplication by a window function
Short-time fourier transform results obtained as a new window function.
Step S23: and calculating a set of chirp rate estimate values for the original echo signal using the first order differential result and the second order differential result.
For gaussian linear modulation signals, the frequency modulation operator is generally used
As instantaneous frequency modulation rate
(instantaneous modulation frequency is derivative of instantaneous frequency)
It is defined as:
wherein the content of the first and second substances,
representing a real part;
can obtain
Estimated value of (a):
it should be noted that the original echo signal has a plurality of instantaneous modulation frequencies, and therefore there are a plurality of calculated estimates, which form a set of modulation frequency estimation values.
Step S24: and carrying out weighted average on the modulation frequency estimation values in the modulation frequency estimation value set, determining a prediction standard deviation based on the weighted average result, and determining the prediction standard deviation as the window length if the prediction standard deviation is smaller than a first threshold value.
For convenience, consider
In discrete form
I.e. the matrix form of the STFT result, will
Also defined as a matrix, then
. In order to enable the optimization algorithm to be more efficient and maintain the consistency of the whole time-frequency domain, the invention carries out weighting and averaging on the estimated frequency values in the estimated frequency value set
：
Wherein the content of the first and second substances,
is a time frequency mask (matrix form) and represents the area in which WBI exists in the time frequency domain;
representing the element-by-element multiplication of the matrix.
Determining a prediction standard deviation based on the result of the weighted average, in particular, by
Giving a reasonable predicted standard deviation.
Specifically, if the predicted standard deviation is smaller than a first threshold, the predicted standard deviation is determined to be the window length, and the original echo signal is processed by using a short-time fourier transform method based on the window length to obtain the two-dimensional time-frequency graph.
If the prediction standard deviation is not smaller than the first threshold value, the process returns to step S21. The window length is calculated in an iterative manner, and the iterative process is explained as follows:
define the result of STFT as
Wherein, in the step (A),
and
are respectively as
Amplitude and phase.
Then, the signal
Instantaneous frequency of
Can be approximated as:
wherein the content of the first and second substances,
in order to be the phase operator,
indicating the real part operation.
Then, define
And introducing group delay
Wherein, in the step (A),
。
on this basis, the frequency modulation rate estimate may be defined as:
in the method and the device, after the window length is determined, the original echo signal is processed by utilizing a short-time Fourier transform method based on the window length to obtain the two-dimensional time-frequency diagram.
Step S13: and detecting the two-dimensional time-frequency diagram to obtain a broadband interference area.
Specifically, in the case where it is assumed that the SAR echo free of interference follows a complex gaussian distribution, since the STFT is a linear transformation, the STFT result of the SAR echo also follows the complex gaussian distribution, and thus the amplitude of the STFT result follows a rayleigh distribution. The wideband interference region detection can be modeled as a binary hypothesis test:
wherein the content of the first and second substances,
、
、
and
STFT results representing SAR echo, useful target echo, noise and WBI, respectively. Under the assumption that
In the following, the first and second parts of the material,
the amplitude of (2) obeys Rayleigh distribution and gives false alarm probability
Threshold of
The calculation is as follows:
wherein the content of the first and second substances,
the parameters of Rayleigh distribution are obtained by adopting first moment estimation, namely:
wherein the content of the first and second substances,
to include for evaluation
The vector of time-frequency bins of (a),
representing the average of the subtended quantities. Ideally, a vector
Does not contain WBI, however, for the SAR echo signal with WBI, the threshold should be used firstly
And detecting the time frequency point containing the WBI. In this regard, the present invention contemplates an algorithm for detecting WBI. The specific process is as follows: determining a threshold value, wherein the threshold value is related to the precision of the broadband interference region; and detecting the two-dimensional time-frequency graph based on the threshold value by using a broadband detection algorithm to obtain a broadband interference area.
Specifically, please refer to fig. 3, which includes:
step S31: calculating by using the initial Rayleigh distribution parameter to obtain an initial threshold value; the initial Rayleigh distribution parameter is determined based on the two-dimensional time-frequency diagram.
First, will
Vectorizing and sorting in ascending order to obtain
And
，
is composed of
Is represented by a vectorization of (a),
is composed of
The sorted result is used for calculating the initial Rayleigh distribution parameter
And initial threshold values:
wherein the content of the first and second substances,
is the initial threshold value of the threshold value,
is a vector
From the first element to the second
The interception of the individual elements is carried out,
，
is composed of
The length of (a) of (b),
is a proportionality coefficient, namely the estimation of the proportion of the interference-free points on the frequency plane,
indicating a rounding off. In the present invention, is provided
Because the present invention assumes that the power of the WBI is higher than that of the useful target echo and noise, and that the time-frequency points where the WBI exists only occupy
A fraction of (a).
Step S32: and determining a time-frequency mask matrix based on the initial threshold value and the two-dimensional time-frequency graph, and determining a complementary time-frequency mask matrix based on the time-frequency mask matrix.
In an embodiment, a time-frequency mask is determined based on the initial threshold value and the two-dimensional time-frequency graph
Matrix:
further determining a complementary time-frequency mask matrix based on the time-frequency mask matrix:
wherein the content of the first and second substances,
for complementary time-frequency masksThe operation of the membrane is carried out by the operator,
the superscript indicates the number of iterations.
Step S33: and determining a predicted Rayleigh distribution parameter based on the two-dimensional time-frequency graph and the complementary time-frequency mask matrix.
Specifically, STFT results are recorded
(i.e. two-dimensional time-frequency diagram) and complementary time-frequency mask
Multiplying point by point to extract time frequency point composition vector without WBI
. Then, estimating and determining the predicted Rayleigh distribution parameters
：
Step S34: and determining a final threshold value based on the predicted Rayleigh distribution parameter, wherein if the final threshold value is smaller than a second threshold value, the final threshold value is determined to be the threshold value.
Determining a final threshold based on the predicted Rayleigh distribution parameter
The method specifically comprises the following steps:
at this time, whether the final threshold value is smaller than a second threshold value is determined, and if yes, the final threshold value is determined to be the threshold value. If not, returning to execute the step S31 until the final threshold value is smaller than the second threshold value, detecting the two-dimensional time-frequency diagram based on the threshold value by using a broadband detection algorithm to obtain a broadband interference area, so that a high-precision broadband interference area can be obtained.
Step S14: and reconstructing the broadband interference area to obtain a reconstructed echo signal.
Time-frequency analysis is the core of non-stationary signal processing. According to the uncertainty principle, the time-frequency result generated by the traditional linear time-frequency analysis method (such as short-time Fourier transform, wavelet transform and the like) has lower resolution. In order to improve the resolution of the conventional time-frequency analysis method, some post-processing methods are proposed. The SST (synchronous queezing Transform, SST) not only can refine the result of a time-frequency domain, but also can extract a mode from the result, and then the expanded SST2 can be better suitable for emphasizing frequency signals, so that in the invention, an STT 2 method based on STFT is adopted and combined with a multiple synchronous compression technology to obtain an MSST2 (second-order multiple synchronous compression Transform) method so as to improve the resolution of the time-frequency result.
Before introducing the STFT-based SST2 method, a second-order instantaneous frequency estimation method is introduced:
wherein the content of the first and second substances,
；
next, a definition of the STFT-based SST2 method is given:
wherein the content of the first and second substances,
representing the window function in the STFT,
the threshold is represented by a number of bits representing the threshold,
the accuracy of the representation is such that,
a window function is represented. When the threshold and the precision approach zero, the above definition can be simplified as:
in the present invention, the calculation region of the above formula is determined by a time-frequency mask. In addition, the signal
To (1) a
The individual components may be reconstructed by:
wherein, the first and the second end of the pipe are connected with each other,
is that
To (1) a
The instantaneous frequency of the individual components is,
is a threshold.
Specifically, in one embodiment, compression parameters are determined; refining the time-frequency mask matrix by using the compression parameters to obtain a refined time-frequency mask matrix; and reconstructing the refined time-frequency mask matrix based on the compression parameters to obtain a reconstructed echo signal. Referring to fig. 4, the step of determining the compression parameters includes:
step S41: defining a frequency resolution matrix and a time resolution matrix; the frequency resolution matrix comprises frequency resolution parameters corresponding to the two-dimensional time-frequency graph, and the time resolution matrix comprises time resolution parameters corresponding to the two-dimensional time-frequency graph.
Specifically, for convenience, first, two matrices are defined
And
。
is a frequency resolution matrix comprising frequency resolution parameters corresponding to the two-dimensional time frequency map, in particular,
each column of (a) contains frequency-resolved parameters corresponding to the STFT results.
Is a time resolution matrix comprising time resolution parameters corresponding to said two-dimensional time-frequency map, in particular,
each row of (a) contains time-resolved parameters corresponding to the STFT results.
Defining a set of frequency-resolving parameters as
The set of time-resolved parameters is
Two, twoThe size of each set is
And
. The number of iterations is defined as
。
Step S42: and constructing a reference matrix based on the frequency resolution matrix and the time resolution matrix, wherein the size of the reference matrix is determined based on the size of the frequency resolution matrix and the size of the time resolution matrix.
Specifically, consider a discrete form of a second order instantaneous frequency calculation formula:
then, a size of
Reference matrix of
In particular, the size of the reference matrix is based on the size of the frequency-resolved matrix
And the size of the time-resolved matrix
And (5) determining.
Step S43: determining the compression parameters based on the reference matrix.
Specifically, a variable matrix is set
Each iteration is right
A new value is assigned. First of all, initializing
Then, traverse the time-frequency mask matrix
All elements equal to 1 in
，
Representing a second order instantaneous frequency matrix (
,
) Elements in collections
In finding the closest
Element of (2), record set
Is closest to
Index of elements of
Let us order
Wherein, in the step (A),
representing a reference matrix
In (A) to (A)
，
) The elements of (a) and (b),
representation matrix
In (A) to (A)
,
) The elements are selected from the group consisting of,
in the range of
，
In the range of
，
In the range of
. After the traversal is finished, order
. Then, the above traversal process is repeated
Then, a reference matrix is obtained
，
For the number of iterations, order
And obtaining the processing result of MSST 2.
Note that the number of iterations
Can be set by itself, and in a practical application of the application, the iteration number is set
To 2, a high resolution compression parameter T is obtained, which is represented in matrix form. In the application, the result of the instantaneous frequency estimation and rearrangement operation based on MSST2 is obviously more concentrated than the STFT result, and the energy of WBI is tightly gathered near a time-frequency curve, which is important for accurately extracting WBI.
In the application, after the compression parameter T is determined, the time-frequency mask matrix is refined by using the compression parameter to obtain refinedThen, a time-frequency mask matrix is obtained; and reconstructing the refined time-frequency mask matrix based on the compression parameters to obtain a reconstructed echo signal. Specifically, peak detection is performed on each column in the compression parameters, and the distance peak is larger than the distance peak
Is at a time-frequency point of
Set to zero in the corresponding column. In the present invention, to preserve as much WBI energy as possible while avoiding absorbing the energy of the useful target signal, one would like
Set to 2 points (two frequency resolving cells). The time-frequency mask after thinning is finer.
The results of MSST2 are compared
I.e. compression parameters and refined time-frequency mask
Point-by-point multiplication and summation by columns to reconstruct WBI, the calculation formula is as follows:
wherein the content of the first and second substances,
representing the WBI after reconstruction of the image,
indicating column-wise summation.
Since the STFT approximation of the SAR echo follows a complex gaussian distribution, its contribution to the sum is negligible. In other words,
containing approximately only the energy of WBI.
To improve performance, the reconstructed WBI is optimized by orthogonal projection:
the SAR echo can then be reconstructed by:
wherein the content of the first and second substances,
obtaining a reconstructed echo signal for the original echo signal
。
To further demonstrate the robustness of the interference suppression method proposed by the present invention, in the present invention, WBI with faster frequency variation and WBI with multi-component are suppressed, respectively, wherein in the embodiments of WBI with faster frequency variation, the signal-to-interference ratios of sinusoidally modulated WBI and chirped WBI are-20 dB and-14 dB, respectively; in the multi-component WBI embodiment, the am-fm WBI and two chirp WBI have signal-to-interference ratios of-20 dB and-14 dB, respectively. The results of the reconstruction show that although WBI exhibits strong non-stationarity, the method still maintains the desired performance, accurately suppressing WBI.
Aiming at the SAR interference suppression method based on high-precision time-frequency representation in the embodiment, experimental verification is carried out, and different WBI suppression methods are adopted to compare the suppression performance results; in order to quantitatively evaluate the performance of the proposed method, the error of normalized recovery of the SAR echo is used
(Normalized Recovery Error, NRE), which can be expressed as:
wherein, the first and the second end of the pipe are connected with each other,
is a matrix containing the original SAR echo as its column,
is a matrix containing the recovered SAR echoes,
the Frobenius norm of the matrix is represented.
Experiments prove that the normalized recovery error NRE of the transient frequency spectrum notch is-8.27 dB, the NRE of the transient characteristic subspace filtering is-6.81 dB, the NRE of the iterative adaptive method is-7.37 dB and the NRE of the interference suppression method based on the high-precision time-frequency representation provided by the invention is-9.10 dB, so that the recovery error of the application is the minimum, the suppression method based on the high-precision time-frequency representation provided by the invention has the best suppression effect, and the effectiveness of the invention is verified.
Referring to fig. 5, fig. 5 is a schematic structural diagram of an interference suppression device according to an embodiment of the present invention, which specifically includes: a determination module 51, a processing module 52, a detection module 53 and a reconstruction module 54.
The determining module 51 is configured to determine a window length, where the window length is related to a frequency resolution and a time resolution of the two-dimensional time-frequency graph. In an embodiment, the determining module 51 processes the original echo signal by using a short-time fourier transform method based on an initial standard deviation, so as to obtain a first initial result, where the initial standard deviation is determined based on a sampling frequency of the original echo signal; calculating a first order differential result and a second order differential result of the first initial result; calculating a set of chirp rate estimate values for the original echo signal using the first order differential result and the second order differential result; and carrying out weighted average on the modulation frequency estimation values in the modulation frequency estimation value set, determining a prediction standard deviation based on the weighted average result, and determining the prediction standard deviation as the window length if the prediction standard deviation is smaller than a first threshold value.
The processing module 52 is configured to process the original echo signal based on the window length by using a short-time fourier transform method, so as to obtain a two-dimensional time-frequency diagram.
The detection module 53 is configured to detect the two-dimensional time-frequency diagram to obtain a broadband interference area. Specifically, the detecting module 53 is configured to determine a threshold, where the threshold is related to the accuracy of the broadband interference area; and detecting the two-dimensional time-frequency graph based on the threshold value by using a broadband detection algorithm to obtain a broadband interference area. In one embodiment, the detection module 53 calculates an initial threshold value by using the initial rayleigh distribution parameter; the initial Rayleigh distribution parameter is determined based on the two-dimensional time-frequency diagram; determining a time-frequency mask matrix based on the initial threshold value and the two-dimensional time-frequency graph, and determining a complementary time-frequency mask matrix based on the time-frequency mask matrix; determining a predicted Rayleigh distribution parameter based on the two-dimensional time-frequency graph and the complementary time-frequency mask matrix; and determining a final threshold value based on the predicted Rayleigh distribution parameter, wherein if the final threshold value is smaller than a second threshold value, the final threshold value is determined to be the threshold value.
The reconstruction module 54 is configured to reconstruct the broadband interference region to obtain a reconstructed echo signal. Specifically, the reconstruction module 54 is configured to determine compression parameters; refining the time-frequency mask matrix by using the compression parameters to obtain a refined time-frequency mask matrix; and reconstructing the refined time-frequency mask matrix based on the compression parameters to obtain a reconstructed echo signal. In one embodiment, the reconstruction module 54 defines a frequency-resolved matrix and a time-resolved matrix; the frequency resolution matrix comprises frequency resolution parameters corresponding to the two-dimensional time-frequency graph, and the time resolution matrix comprises time resolution parameters corresponding to the two-dimensional time-frequency graph; constructing a reference matrix based on the frequency resolution matrix and the time resolution matrix, wherein the size of the reference matrix is determined based on the size of the frequency resolution matrix and the size of the time resolution matrix; determining the compression parameters based on the reference matrix.
Fig. 6 is a schematic structural diagram of an electronic device according to an embodiment of the invention. The electronic device comprises a memory 62 and a processor 61 connected to each other.
The memory 62 is used to store program instructions implementing the method of any one of the above.
The processor 61 is operative to execute program instructions stored in the memory 62.
The processor 61 may also be referred to as a CPU (Central Processing Unit). The processor 61 may be an integrated circuit chip having signal processing capabilities. The processor 61 may also be a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The storage 62 may be a memory bank, a TF card, etc., and may store all information in the electronic device, including the input raw data, the computer program, the intermediate operation results, and the final operation results. It stores and retrieves information based on the location specified by the controller. With the memory, the electronic device can only have the memory function to ensure the normal operation. The storage of electronic devices can be classified into a main storage (internal storage) and an auxiliary storage (external storage) according to the use, and also into an external storage and an internal storage. The external memory is usually a magnetic medium, an optical disk, or the like, and can store information for a long period of time. The memory refers to a storage component on the main board, which is used for storing data and programs currently being executed, but is only used for temporarily storing the programs and the data, and the data is lost when the power is turned off or the power is cut off.
In the several embodiments provided in the present application, it should be understood that the disclosed method and apparatus may be implemented by other methods. For example, the above-described apparatus implementation methods are merely illustrative, e.g., the division of modules or units into only one logical functional division, and additional division methods may be implemented in practice, e.g., units or components may be combined or integrated into another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment of the method.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a system server, a network device, or the like) or a processor (processor) to execute all or part of the steps of the implementation method of the present application.
Fig. 7 is a schematic structural diagram of a computer-readable storage medium according to the present invention. The storage medium of the present application stores a program file 71 capable of implementing all the methods, wherein the program file 71 may be stored in the storage medium in the form of a software product, and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute all or part of the steps of each implementation method of the present application. The foregoing storage device includes: various media capable of storing program codes, such as a usb disk, a mobile hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, or terminal devices, such as a computer, a server, a mobile phone, and a tablet.
The above description is only an implementation method of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent flow transformations made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. An interference suppression method, comprising:
determining the window length;
processing the original echo signal by using a short-time Fourier transform method based on the window length to obtain a two-dimensional time-frequency graph;
detecting the two-dimensional time-frequency graph to obtain a broadband interference area;
and reconstructing the broadband interference area to obtain a reconstructed echo signal.
2. The method of claim 1, wherein the window length is related to a frequency resolution and a time resolution of the two-dimensional time-frequency graph.
3. The method of claim 2, wherein the step of determining the window length comprises:
processing the original echo signal by using a short-time Fourier transform method based on an initial standard deviation to obtain a first initial result, wherein the initial standard deviation is determined based on the sampling frequency of the original echo signal;
calculating a first order differential result and a second order differential result of the first initial result;
calculating a set of chirp rate estimate values for the original echo signal using the first order differential result and the second order differential result;
and carrying out weighted average on the modulation frequency estimation values in the modulation frequency estimation value set, determining a prediction standard deviation based on the weighted average result, and determining the prediction standard deviation as the window length if the prediction standard deviation is smaller than a first threshold value.
4. The method according to claim 1, wherein the step of detecting the two-dimensional time-frequency diagram to obtain a wideband interference region comprises:
determining a threshold value, wherein the threshold value is related to the precision of the broadband interference region;
and detecting the two-dimensional time-frequency graph based on the threshold value by using a broadband detection algorithm to obtain a broadband interference area.
5. The method of claim 4, wherein the step of determining the threshold value comprises:
calculating by using the initial Rayleigh distribution parameter to obtain an initial threshold value; the initial Rayleigh distribution parameter is determined based on the two-dimensional time-frequency diagram;
determining a time-frequency mask matrix based on the initial threshold value and the two-dimensional time-frequency graph, and determining a complementary time-frequency mask matrix based on the time-frequency mask matrix;
determining a predicted Rayleigh distribution parameter based on the two-dimensional time-frequency graph and the complementary time-frequency mask matrix;
and determining a final threshold value based on the predicted Rayleigh distribution parameter, wherein if the final threshold value is smaller than a second threshold value, the final threshold value is determined to be the threshold value.
6. The method of claim 5, wherein the step of reconstructing the wide-band interference region to obtain a reconstructed echo signal comprises:
determining a compression parameter;
refining the time-frequency mask matrix by using the compression parameters to obtain a refined time-frequency mask matrix;
and reconstructing the refined time-frequency mask matrix based on the compression parameters to obtain a reconstructed echo signal.
7. The method of claim 6, wherein the step of determining compression parameters comprises:
defining a frequency resolution matrix and a time resolution matrix; the frequency resolution matrix comprises frequency resolution parameters corresponding to the two-dimensional time-frequency graph, and the time resolution matrix comprises time resolution parameters corresponding to the two-dimensional time-frequency graph;
constructing a reference matrix based on the frequency resolution matrix and the time resolution matrix, wherein the size of the reference matrix is determined based on the size of the frequency resolution matrix and the size of the time resolution matrix;
determining the compression parameter based on the reference matrix.
8. An interference suppression apparatus, comprising:
a determining module for determining a window length;
the processing module is used for processing the original echo signal by utilizing a short-time Fourier transform method based on the window length to obtain a two-dimensional time-frequency graph;
the detection module is used for detecting the two-dimensional time-frequency diagram to obtain a broadband interference area;
and the reconstruction module is used for reconstructing the broadband interference area to obtain a reconstructed echo signal.
9. An electronic device comprising a processor and a memory coupled to each other, wherein,
the memory for storing program instructions for implementing the method of any one of claims 1-7;
the processor is configured to execute the program instructions stored by the memory.
10. A computer-readable storage medium, characterized in that a program file is stored, which program file can be executed to implement the method according to any one of claims 1-7.
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Application publication date: 20220906 |