A method and system for terrain clutter suppression of wind profile radar

Abstract

The application discloses a terrain clutter suppression method and system of a wind profile radar, and the method comprises the following steps: 1) representing a wind profile radar receiving signal as a matrix, performing singular value decomposition on the matrix, and setting smaller singular values in the matrix to zero, so as to eliminate large atmospheric wave in the receiving signal, and meanwhile, retain terrain clutter in the receiving signal; 2) performing Fourier transform on the receiving signal with the retained terrain clutter to obtain a frequency spectrum, and obtaining frequencies and amplitudes of a plurality of stronger frequency spectrum components according to the distribution characteristics of the frequency spectrum; and 3) constructing a terrain clutter estimation by using the obtained frequencies and amplitudes, subtracting the terrain clutter estimation from the wind profile radar receiving signal, so as to suppress the terrain clutter, and obtain clean large atmospheric wave. The application can effectively suppress strong terrain clutter mixed in the wind profile radar receiving signal, and obtain clean large atmospheric wave, thereby providing strong guarantee for accurate weather forecast.

Description

Technical Field

[0001] This invention relates to ground clutter suppression, specifically a method and system for ground clutter suppression in wind profiler radar. Background Technology

[0002] When a wind profiler radar operates, it emits a series of coherent pulses into the air. These pulses are scattered by inhomogeneities in the turbulent atmosphere, and the backscattered echoes are received by the radar. The radar processes these echo signals to obtain meteorological information such as the horizontal wind field, vertical airflow, and atmospheric refractive index structure constant. At close range, in addition to atmospheric echoes, the radar also receives strong echoes reflected from ground objects, i.e., ground clutter. Ground clutter typically resides near zero frequency in the Doppler frequency domain. When the Doppler frequency of the atmospheric echoes is low, it can alias with ground clutter, thus affecting the radar's extraction of various meteorological information.

[0003] Ground clutter suppression in wind profiler radar is a widely concerned issue. The literature (Hu Mingbao. Wind Profiler Radar Detection and Application [M]. Beijing: Meteorological Press, 2015.) introduces the application effect of wavelet technology for clutter removal. However, after repeated experiments, the authors believe that it is difficult to find a wavelet basis suitable for the analysis of measured wind profiler radar signal spectrum. The literature (Siggia AD, Passarelli RE Jr. Gaussian model adaptive processing (GMAP) for improved ground clutter cancellation and moment calculation [C]. MS-NR:ERAD3-P-00117, 2005) presents a method for clutter removal in the Doppler frequency domain, which has certain practicality. However, this method will cause local distortion of the atmospheric echo spectrum in the clutter region, and its repeated recursive processing increases the complexity of application. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for suppressing ground clutter in wind profiler radar, which can effectively suppress strong ground clutter superimposed on the received signal of wind profiler radar and obtain clean atmospheric echoes. These atmospheric echoes can then be used to estimate meteorological elements such as horizontal wind field, vertical airflow, and atmospheric refractive index structure constant, providing strong support for accurate weather forecasting.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for suppressing ground clutter in wind profiler radar includes the following steps:

[0007] 1) Represent the wind profiler radar received signal as a matrix, perform singular value decomposition on the matrix, set the smaller singular values ​​to zero, eliminate atmospheric echoes in the received signal, and retain ground clutter in the received signal.

[0008] 2) Perform a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtain the frequency and amplitude of multiple spectral components based on the distribution characteristics of the spectrum;

[0009] 3) Construct ground clutter estimates using the obtained multiple frequencies and amplitudes, and subtract the ground clutter estimates from the wind profiler radar received signals to obtain clean atmospheric echoes.

[0010] Further, step 1) represents the wind profiler radar received signal as a matrix, performs singular value decomposition on the matrix, sets the smaller singular values ​​to zero, eliminates atmospheric echoes in the received signal, and retains ground clutter in the received signal. Specifically, this includes the following steps:

[0011] 1-1) Assume the wind profiler radar receives the signal as follows: ,in Atmospheric echo, For ground feature clutter, For background noise, Let be the signal length; , and All are positive integers, Represent as matrix for:

[0012] ;

[0013] 1-2) For the matrix Perform singular value decomposition:

[0014] ;

[0015] In the formula: for unitary matrix, for unitary matrix, for diagonal matrix, , Indicates diagonalization, It is a singular value. The number of singular values. , This indicates taking the smaller value. It is a zero matrix, and the superscript H indicates the conjugate transpose;

[0016] 1-3) Singular values ​​smaller than the threshold are set to zero, resulting in a new diagonal matrix. ,use replace ,get:

[0017] ;

[0018] In the formula: .

[0019] Furthermore, the threshold is taken as One-fifth of the largest singular value.

[0020] Further, step 2) involves performing a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and then obtaining the frequency and amplitude of several stronger spectral components based on the distribution characteristics of this spectrum. Specifically, this includes the following steps:

[0021] 2-1) To Perform a Fourier transform to obtain the spectrum. ,in The pulse repetition period of the radar has a spectral amplitude of... , The frequency corresponding to the maximum value is ;

[0022] 2-2) Constructing vectors , obtain amplitude , where vector superscript Indicates transpose;

[0023] 2-3) Constructing time-domain signals ,from Subtract ,get ;

[0024] 2-4) Use replace Return to step 2-1), and repeat steps 2-1) through 2-3). Next, get indivual frequency and Amplitude , .

[0025] Furthermore, iteration The next With iteration The next The norm of the difference is less than the set value.

[0026] Furthermore, the set value is 0.01.

[0027] Further, step 3) involves constructing a ground clutter estimate using the obtained multiple frequencies and amplitudes, and subtracting the ground clutter estimate from the wind profiler radar received signal to obtain a clean atmospheric echo. This specifically includes the following steps:

[0028] 3-1) Structural clutter estimation for:

[0029] ;

[0030] 3-2) Receiving signals from radar Subtract The clean atmospheric echo signal obtained is:

[0031] .

[0032] After processing, the strong ground clutter in the wind profiler radar received signal was effectively suppressed, significantly reducing its impact on atmospheric echoes. Therefore, it can be utilized... To estimate meteorological information such as atmospheric horizontal wind field, vertical airflow, and atmospheric refractive index structure constant.

[0033] A ground clutter suppression system for wind profiler radar includes:

[0034] The wind profiler radar received signal decomposition unit represents the wind profiler radar received signal as a matrix, performs singular value decomposition on the matrix, sets the smaller singular values ​​to zero, eliminates atmospheric echoes in the received signal, and retains ground clutter in the received signal.

[0035] The frequency and amplitude calculation unit performs a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtains the frequency and amplitude of multiple spectral components based on the distribution characteristics of the spectrum.

[0036] The ground clutter unit is used to construct a ground clutter estimate using multiple frequencies and amplitudes. The ground clutter estimate is then subtracted from the wind profiler radar signal to obtain a clean atmospheric echo.

[0037] A ground clutter suppression device for a wind profiler radar includes: a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the ground clutter suppression method.

[0038] A computer storage medium storing an executable program, the executable program being executed by a processor to implement the steps of the ground clutter suppression method.

[0039] Compared with the prior art, the advantages of this invention are: (1) It can effectively suppress strong ground clutter in radar received signals, while having little effect on atmospheric echoes, which can be ignored; (2) The spectrum of ground clutter can be calculated using fast Fourier transform, so the calculation efficiency is high; (3) Each processing step is very robust, so the reliability of operation is very high. Attached Figure Description

[0040] Figure 1 This is a flowchart of a ground clutter suppression method for a wind profiler radar according to the present invention.

[0041] Figure 2 This is a comparison chart of the atmospheric velocity spectrum generated and estimated for the ground clutter suppression method of the wind profiler radar of the present invention.

[0042] Figure 3 This is a comparison diagram of the generated and estimated ground object velocity spectrum for the ground object clutter suppression method of the wind profiler radar of the present invention.

[0043] Figure 4 This is a comparison diagram of velocity spectra before and after clutter suppression in a ground clutter suppression method for a wind profiler radar according to the present invention. Detailed Implementation

[0044] The present invention will now be further described with reference to the accompanying drawings.

[0045] This invention provides a method for suppressing ground clutter in wind profiler radar. It can effectively suppress strong ground clutter in radar received signals, while having a negligible impact on atmospheric echoes. The ground clutter spectrum can be calculated using fast Fourier transform, resulting in high computational efficiency. Each processing step is robust, thus ensuring high operational reliability.

[0046] Combination Figure 1 This invention proposes a method for suppressing ground clutter in wind profiler radar, comprising the following steps:

[0047] 1) Represent the wind profiler radar received signal as a matrix, perform singular value decomposition on the matrix, and set the smaller singular values ​​to zero, thereby eliminating atmospheric echoes in the received signal while retaining ground clutter; specifically,

[0048] 1-1) Assume the wind profiler radar receives the signal as follows: ,in Atmospheric echo, For ground feature clutter, For background noise, Let be the signal length; , and All are positive integers, Represent as matrix ,

[0049] (1)

[0050] 1-2) For the matrix Perform singular value decomposition.

[0051] (2)

[0052] In the formula: for unitary matrix, for unitary matrix, for diagonal matrix, , Indicates diagonalization, It is a singular value. The number of singular values. , This indicates taking the smaller value. It is a zero matrix with appropriate dimensions, and the superscript H denotes the conjugate transpose;

[0053] 1-3) Singular values ​​smaller than the threshold are set to zero, resulting in a new diagonal matrix. Use it to replace the one in equation (2) ,get

[0054] (3)

[0055] In equation (3), atmospheric echoes are basically eliminated, but ground clutter is retained, thus yielding .

[0056] The general threshold is taken as follows One-fifth of the largest singular value.

[0057] 2) Perform a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtain the frequency and amplitude of several strong spectral components based on the distribution characteristics of the spectrum; specifically,

[0058] 2-1) To Perform a Fourier transform to obtain the spectrum. ,in The pulse repetition period of the radar has a spectral amplitude of... , The frequency corresponding to the maximum value ;

[0059] 2-2) Constructing vectors , obtain amplitude , where vector superscript Indicates transpose;

[0060] 2-3) Constructing time-domain signals , and then from Subtract ,get ;

[0061] 2-4) Use replace Return to step 2-1), and repeat steps 2-1) through 2-3). Next, get indivual frequency and Amplitude , .

[0062] Iteration The next With iteration The next The norm of the difference is less than a set value, which can be 0.01.

[0063] 3) Ground clutter estimates are constructed using multiple obtained frequencies and amplitudes. These estimates are then subtracted from the wind profiler radar signal, thereby suppressing ground clutter and obtaining a clean atmospheric echo. Specifically,

[0064] 3-1) Structural clutter estimation ,

[0065] (4)

[0066] 3-2) Receiving signals from radar Subtract ,

[0067] (5)

[0068] After processing by equation (5), the strong ground clutter in the wind profiler radar received signal is effectively suppressed, significantly reducing its impact on atmospheric echoes. Therefore, it can be utilized... To estimate meteorological information such as atmospheric horizontal wind field, vertical airflow, and atmospheric refractive index structure constant.

[0069] A ground clutter suppression method for wind profiler radar according to the present invention was simulated, and the ground clutter suppression method of the present invention was verified through simulation examples.

[0070] The first step is to generate the wind profiler radar received signal using existing methods. The power spectrum of the radar received signal is as follows: ,in, For interval Random numbers that are uniformly distributed on the upper surface. For signal power, The average Doppler frequency of the signal. For the spectral width of the signal, The power of the background noise; the phase spectrum of the radar received signal is The spectrum of the radar received signal is then...

[0071] (6)

[0072] When generating atmospheric echo signals, assume , , , ,wavelength The average speed of the atmosphere The velocity spectrum width is Substituting these parameters into equation (6) yields the spectrum of the atmospheric echo. After discretization, a discrete spectrum is obtained. An inverse Fourier transform is performed on the discrete spectrum to obtain a discrete time series. The first segment of this series is extracted as the desired atmospheric echo. A Fourier transform is performed on the atmospheric echo to obtain its spectrum, i.e., the atmospheric velocity spectrum, whose amplitude is as follows: Figure 2 As shown by the solid line; when generating ground clutter, assume , , , ,wavelength Then the average speed of the ground features The velocity spectrum width is Substituting these parameters into equation (6) yields the spectrum of ground clutter. After discretization, a discrete spectrum is obtained. An inverse Fourier transform is performed on the discrete spectrum to obtain a discrete time series. Similarly, the first segment of this series is extracted as the desired ground clutter. A Fourier transform is performed on the ground clutter to obtain its spectrum, i.e., the velocity spectrum of the ground clutter, whose amplitude is as follows: Figure 3 As shown by the solid line; the intercepted atmospheric echoes and ground clutter are superimposed to form the desired wind profiler radar received signal. A Fourier transform is performed on the wind profiler radar received signal to obtain the spectrum, and the spectrum amplitude is as follows. Figure 4 As shown by the solid line in the image.

[0073] The second step involves suppressing ground clutter using a ground clutter suppression method for wind profiler radar according to the present invention. First, the radar received signal is represented as a matrix. Singular value decomposition is performed on this matrix, and smaller singular values ​​are set to zero, thereby eliminating atmospheric echoes in the received signal while retaining ground clutter. Then, a Fourier transform is performed on the received signal with retained ground clutter to obtain its spectrum. Based on the distribution characteristics of this spectrum, the frequencies and amplitudes of several stronger spectral components are obtained. Finally, ground clutter estimates are constructed using the obtained frequencies and amplitudes (spectral data is shown in the image). Figure 3 (As shown by the dashed line in the middle), the ground clutter estimate is subtracted from the wind profiler radar received signal, thereby suppressing the ground clutter and obtaining a clean atmospheric echo (spectral density as shown in the image). Figure 4 (As shown by the dashed line).

[0074] exist Figure 3 In the diagram, the estimated ground object velocity spectrum peak shown by the dashed line is very close to the generated ground object velocity spectrum peak shown by the solid line, indicating that the estimation of ground object clutter in this invention is very accurate. When the ground object clutter estimate is subtracted from the radar received signal, the... Figure 4 It is evident that ground clutter was effectively suppressed, while its impact on atmospheric echoes was minimal and negligible. This can also be seen from... Figure 2 As can be seen, the estimated atmospheric velocity spectrum peak shown by the dashed line is very close to the generated atmospheric velocity spectrum peak shown by the solid line.

[0075] The present invention also provides a ground clutter suppression system for wind profiler radar, comprising:

[0076] The wind profiler radar received signal decomposition unit represents the wind profiler radar received signal as a matrix, performs singular value decomposition on the matrix, sets the smaller singular values ​​to zero, eliminates atmospheric echoes in the received signal, and retains ground clutter in the received signal.

[0077] The frequency and amplitude calculation unit performs a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtains the frequency and amplitude of multiple spectral components based on the distribution characteristics of the spectrum.

[0078] The ground clutter unit is used to construct a ground clutter estimate using multiple frequencies and amplitudes. The ground clutter estimate is then subtracted from the wind profiler radar signal to obtain a clean atmospheric echo.

[0079] The present invention provides an exemplary ground clutter suppression device for wind profiler radar, comprising: a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the ground clutter suppression method.

[0080] The present invention provides, by way of example, a computer storage medium storing an executable program, which is executed by a processor to implement the steps of the ground clutter suppression method described above.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing ground clutter in wind profiler radar, characterized in that, Includes the following steps: 1) Represent the wind profiler radar received signal as a matrix, perform singular value decomposition on the matrix, set the smaller singular values ​​to zero, eliminate atmospheric echoes in the received signal, and retain ground clutter in the received signal. 2) Perform a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtain the frequency and amplitude of multiple spectral components based on the distribution characteristics of the spectrum; 3) Construct ground clutter estimates using the obtained multiple frequencies and amplitudes, and subtract the ground clutter estimates from the wind profiler radar received signals to obtain clean atmospheric echoes.

2. The ground clutter suppression method for wind profiler radar according to claim 1, characterized in that: Step 1) represents the wind profiler radar received signal as a matrix, performs singular value decomposition on the matrix, sets the smaller singular values ​​to zero, eliminates atmospheric echoes in the received signal, and retains ground clutter in the received signal. This specifically includes the following steps: 1-1) Assume the wind profiler radar receives the signal as follows: ,in Atmospheric echo, For ground feature clutter, For background noise, Let be the signal length; , and All are positive integers, Represent as matrix for: ； 1-2) For the matrix Perform singular value decomposition: ； In the formula: for unitary matrix, for unitary matrix, for diagonal matrix, , Indicates diagonalization, It is a singular value. The number of singular values. , This indicates taking the smaller value. It is a zero matrix, and the superscript H indicates the conjugate transpose; 1-3) Singular values ​​smaller than the threshold are set to zero, resulting in a new diagonal matrix. ,use replace ,get: ； In the formula: .

3. The ground clutter suppression method for wind profiler radar according to claim 2, characterized in that: The threshold is taken One-fifth of the largest singular value.

4. The ground clutter suppression method for wind profiler radar according to claim 2, characterized in that: Step 2) involves performing a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum. Based on the distribution characteristics of this spectrum, the frequencies and amplitudes of multiple spectral components are obtained. Specifically, this includes the following steps: 2-1) To Perform a Fourier transform to obtain the spectrum. ,in The pulse repetition period of the radar has a spectral amplitude of... , The frequency corresponding to the maximum value is ; 2-2) Constructing vectors , obtain amplitude , where vector superscript Indicates transpose; 2-3) Constructing time-domain signals ,from Subtract ,get ; 2-4) Use replace Return to step 2-1), and repeat steps 2-1) through 2-3). Next, get indivual frequency and Amplitude , .

5. A method for suppressing ground clutter in a wind profiler radar according to claim 4, characterized in that: Iteration The next With iteration The next The norm of the difference is less than the set value.

6. A method for suppressing ground clutter in a wind profiler radar according to claim 5, characterized in that: The set value is 0.

01.

7. A method for suppressing ground clutter in a wind profiler radar according to claim 4, characterized in that: Step 3) involves constructing a ground clutter estimate using the obtained multiple frequencies and amplitudes, and subtracting the ground clutter estimate from the wind profiler radar received signal to obtain a clean atmospheric echo. This step specifically includes the following steps: 3-1) Structural clutter estimation for: ； 3-2) Receiving signals from radar Subtract The clean atmospheric echo signal obtained is: 。 8. A ground clutter suppression system for a wind profiler radar implementing the method of any one of claims 1-7, characterized in that, include: The wind profiler radar received signal decomposition unit represents the wind profiler radar received signal as a matrix, performs singular value decomposition on the matrix, sets the smaller singular values ​​to zero, eliminates atmospheric echoes in the received signal, and retains ground clutter in the received signal. The frequency and amplitude calculation unit performs a Fourier transform on the received signal of the retained ground clutter to obtain its spectrum, and obtains the frequency and amplitude of multiple spectral components based on the distribution characteristics of the spectrum. The ground clutter unit is used to construct a ground clutter estimate using multiple frequencies and amplitudes. The ground clutter estimate is then subtracted from the wind profiler radar signal to obtain a clean atmospheric echo.

9. A ground clutter suppression device for wind profiler radar, characterized in that, include: A memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the ground clutter suppression method according to any one of claims 1-7.

10. A computer storage medium, characterized in that, The computer storage medium stores an executable program, which is executed by a processor to implement the steps of the ground clutter suppression method according to any one of claims 1-7.

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