Strong ground object Doppler sidelobe suppression method and system based on window function frequency domain processing

Abstract

The present invention relates to a method and system for suppressing Doppler sidelobes of strong ground objects based on frequency domain processing of a window function, and belongs to the field of radar signal processing. The method obtains sidelobe threshold coefficients for each Doppler channel of all range units based on the window function by performing a series of processes such as Fourier transform on the window function added to the echo data after pulse compression. The method includes the following steps: obtaining a frequency domain window function by Fourier transforming the window function added to the echo data after pulse compression; obtaining a system noise mean by statistics; adding the system noise mean to the frequency domain window function as a whole, and setting the amplitude of Doppler channel 0 to 0 to obtain a sidelobe threshold coefficient; and determining whether the threshold value of any Doppler channel is greater than the amplitude value of the channel. The method solves the problem that existing methods have poor suppression effect on Doppler sidelobes of strong ground objects, and greatly reduces the false alarm rate of target detection near Doppler channel 0 under strong ground clutter background.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing, and in particular to a method and system for suppressing Doppler side lobes of strong ground objects based on window function frequency domain processing. Background Art

[0002] Doppler sidelobe suppression of strong ground objects has long been an important research topic in radar signal processing. When the target of interest is a small, slow, low-speed target with low velocity, small size, and close to the ground, its echo signal is often obscured by the Doppler sidelobes of the strong ground objects. Therefore, in order to extract the target signal of interest, it is of great significance to suppress the Doppler sidelobes of the strong ground objects near Doppler channel 0.

[0003] After matched filtering, the pulse compression signal, after MTD processing, has high Doppler sidelobes in the output signal, hindering target detection near Doppler channel 0. Currently, a common approach to addressing this issue is to window the pulse compression output signal, using common methods such as Hamming, Taylor, and Chebyshev windows. However, in practice, windowing alone is ineffective in suppressing sidelobes and may even result in a reduced mainlobe-to-sidelobe ratio and a widening of the mainlobe, increasing the false alarm rate for target detection near Doppler channel 0.

[0004] Because the pulse compression output signal is windowed before MTD is performed in radar signal processing, the ground object near Doppler channel 0 should have spectral characteristics similar to those of the window function. Therefore, to effectively suppress the Doppler sidelobes of strong ground objects, based on the spectral characteristics of the window function applied to the echo data after pulse compression, the sidelobe threshold coefficient for each Doppler channel of all range cells based on this window function can be obtained. Furthermore, the sidelobes can be suppressed by determining whether the threshold value of any Doppler channel is greater than the amplitude value of that channel. Summary of the Invention

[0005] The technical problems to be solved by the present invention are:

[0006] The echo signals of small, slow, and low-speed targets near strong ground objects, characterized by low speed, small size, and close ground motion, are often obscured by the Doppler sidelobes of the strong ground objects. To address the shortcomings of the existing technology, the present invention proposes a method and system for suppressing Doppler sidelobes of strong ground objects based on frequency domain processing using a window function.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing, characterized in that:

[0009] Acquire the echo data of strong ground objects and perform pulse compression on the echo data;

[0010] Performing Fourier transform on the window function added to the echo data after pulse compression to obtain a frequency domain window function;

[0011] The sidelobe threshold coefficient is obtained based on the frequency domain window function and the system noise average value;

[0012] A sidelobe threshold value is obtained based on a sidelobe threshold value coefficient;

[0013] Doppler sidelobes are suppressed based on a Doppler sidelobe threshold.

[0014] A further technical solution of the present invention is: the frequency domain window function is obtained by Fourier transforming the window function added to the echo data after pulse compression, specifically:

[0015] After Fourier transforming the window function W(n) in the time domain of the echo data after pulse compression, the frequency domain expression is W(f)=FFt{W(n)};

[0016] Set the Doppler channel 0 to 0 to obtain the frequency domain window function:

[0017]

[0018] Where M is the window length.

[0019] A further technical solution of the present invention is: the sidelobe threshold coefficient is obtained based on the frequency domain window function and the system noise, specifically:

[0020] Statistical MTD level system noise mean n s ;

[0021] Add the system noise mean n to the frequency domain window function s , the sidelobe threshold coefficient of each Doppler channel of all range units is W(f)+n s .

[0022] A further technical solution of the present invention is: the sidelobe threshold value is obtained based on the sidelobe threshold value coefficient, specifically:

[0023] Multiplying the sidelobe threshold coefficient by the amplitude value Amp0 of any range unit in the 0th Doppler channel gives the sidelobe threshold value of the range unit on the fth filter channel:

[0024] S dop =Amp0×(W(f)+n s ).

[0025] A further technical solution of the present invention is: the Doppler sidelobe suppression based on the Doppler sidelobe threshold is specifically as follows:

[0026] Determine whether the Doppler sidelobe threshold value of any Doppler channel is greater than the amplitude value of the channel: If the Doppler sidelobe threshold value is greater than the amplitude value, that is, S dop >Amp f , then the point can be considered as a Doppler sidelobe rather than a target, where Amp f is the amplitude value of the f-th Doppler channel.

[0027] A strong ground object Doppler sidelobe suppression system based on window function frequency domain processing, characterized by comprising:

[0028] Pulse compression module, used to obtain echo data of strong ground objects and perform pulse compression on the echo data;

[0029] A Fourier transform module is used to perform Fourier transform on the window function added to the echo data after pulse compression to obtain a frequency domain window function;

[0030] A sidelobe threshold coefficient calculation module is used to obtain the sidelobe threshold coefficient of each Doppler channel of all range units based on the frequency domain window function and the system noise average value;

[0031] A sidelobe threshold value calculation module, used to obtain a sidelobe threshold value based on a sidelobe threshold value coefficient;

[0032] The Doppler sidelobe suppression module is used to suppress the Doppler sidelobe based on the Doppler sidelobe threshold.

[0033] The beneficial effects of the present invention are:

[0034] The present invention provides a method and system for suppressing Doppler sidelobes of strong ground objects based on window function frequency domain processing. The method obtains sidelobe threshold coefficients of each Doppler channel of all distance units based on the window function by performing a series of processing such as Fourier transform on the echo data added to the pulse compressed window function. The sidelobe threshold value is obtained based on the sidelobe threshold coefficient, and the Doppler sidelobes are suppressed according to the sidelobe threshold value.

[0035] The method of the present invention solves the problem that the traditional method has poor suppression effect on the Doppler sidelobes of strong ground objects in actual engineering applications, and greatly reduces the false alarm rate of target detection near the No. 0 Doppler channel under the background of strong ground clutter. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0037] Figure 1 Flowchart of the steps of the method of the present invention.

[0038] Figure 2The sidelobe threshold coefficient of the Doppler channel of the window function.

[0039] Figure 3 To collect strong ground object echo data.

[0040] Figure 4 The sidelobe threshold is compared with the echo data. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0042] Example 1:

[0043] The present invention proposes a method for suppressing Doppler sidelobes of strong ground objects based on frequency domain processing using a window function. This method utilizes the fact that windowing is performed on the pulse compression output signal before MTD is performed in radar signal processing. The ground objects near Doppler channel 0 should have spectral characteristics similar to those of the window function. To effectively suppress the Doppler sidelobes of strong ground objects, the sidelobe threshold coefficient for each Doppler channel in all range units based on the window function is determined by analyzing the spectral characteristics of the window function applied to the echo data after pulse compression. Furthermore, sidelobe suppression can be performed by determining whether the threshold value of any Doppler channel is greater than the amplitude value of that channel.

[0044] like Figure 1 As shown in FIG, the basic steps of the method for suppressing the Doppler sidelobe of strong ground objects based on frequency domain processing of the window function are described.

[0045] In step S101, a series of processing such as Fourier transform is performed on the window function added to the echo data after pulse compression to obtain the sidelobe threshold coefficient of each Doppler channel of all range cells based on the window function.

[0046] It is known that the time domain expression of the window function added to the echo data after pulse compression is W(n). After Fourier transforming the window function, the frequency domain expression is W(f)=FFt{W(n)}. In order not to affect the target detection result on Doppler channel 0, Doppler channel 0 is set to 0, that is (where M is the window length):

[0047]

[0048] In step S102, the mean value of the system noise at the MTD level n is calculated. s , the system noise with clean background should be counted. Add the mean system noise n to the result of step 1.s , we can get the sidelobe threshold coefficient of each Doppler channel of all range units as W(f)+n s , and save the threshold coefficient in the processor; here taking the Hamming window as an example, the sidelobe threshold coefficient of the Doppler channel is as follows Figure 2 As shown in FIG, the Doppler sidelobe threshold coefficient is the sidelobe threshold coefficient for the entire range.

[0049] In step S103, it is known that the amplitude value of any distance unit in Doppler channel 0 is Amp0, such as Figure 3 As shown in the figure, the strong ground object echo data collected in the experiment, the sidelobe threshold value on the f-th filter channel of the range unit can be obtained as follows:

[0050] S dop =Amp0×(W(f)+n s ).

[0051] In step S103, the method of suppressing the Doppler sidelobe by using the Doppler sidelobe threshold calculated in step S103 is to determine whether the threshold value of any Doppler channel is greater than the amplitude value of the channel. Figure 4 As shown, if the threshold value is greater than the amplitude value, that is, S dop >Amp f (Amps f is the amplitude value of the fth Doppler channel), then the point can be considered as a Doppler sidelobe rather than a target.

[0052] Example 2:

[0053] The present invention also provides a strong ground object Doppler sidelobe suppression system based on window function frequency domain processing, comprising:

[0054] Pulse compression module, used to obtain echo data of strong ground objects and perform pulse compression on the echo data;

[0055] A Fourier transform module is used to perform Fourier transform on the window function added to the echo data after pulse compression to obtain a frequency domain window function;

[0056] A sidelobe threshold coefficient calculation module is used to obtain the sidelobe threshold coefficient of each Doppler channel of all range units based on the frequency domain window function and the system noise average value;

[0057] A sidelobe threshold value calculation module, used to obtain a sidelobe threshold value based on a sidelobe threshold value coefficient;

[0058] The Doppler sidelobe suppression module is used to suppress the Doppler sidelobe based on the Doppler sidelobe threshold.

[0059] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing, characterized in that: Acquire the echo data of strong ground objects and perform pulse compression on the echo data; Performing Fourier transform on the window function added to the echo data after pulse compression to obtain a frequency domain window function; The sidelobe threshold coefficient is obtained based on the frequency domain window function and the system noise average value; A sidelobe threshold value is obtained based on a sidelobe threshold value coefficient; Doppler sidelobes are suppressed based on a Doppler sidelobe threshold.

2. The method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing according to claim 1, characterized in that: The frequency domain window function is obtained by Fourier transforming the window function added to the echo data after pulse compression, specifically: After Fourier transforming the window function W(n) in the time domain of the echo data after pulse compression, the frequency domain expression is W(f)=FFt{W(n)}; Set the Doppler channel 0 to 0 to obtain the frequency domain window function: Where M is the window length.

3. The method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing according to claim 2, characterized in that: The sidelobe threshold coefficient is obtained based on the frequency domain window function and the system noise, specifically: Statistical MTD level system noise mean n s ; Add the system noise mean n to the frequency domain window function s , the sidelobe threshold coefficient of each Doppler channel of all range units is W(f)+n s .

4. The method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing according to claim 3, characterized in that: The sidelobe threshold value is obtained based on the sidelobe threshold value coefficient, specifically: Multiplying the sidelobe threshold coefficient by the amplitude value Amp0 of any range unit in the 0th Doppler channel gives the sidelobe threshold value of the range unit on the fth filter channel: S dop =Amp0×(W(f)+n s )。 5. The method for suppressing Doppler sidelobe of strong ground objects based on window function frequency domain processing according to claim 1, characterized in that: The Doppler sidelobe suppression based on the Doppler sidelobe threshold is specifically as follows: Determine whether the Doppler sidelobe threshold value of any Doppler channel is greater than the amplitude value of the channel: If the Doppler sidelobe threshold value is greater than the amplitude value, that is, S dop >Amp f , then the point can be considered as a Doppler sidelobe rather than a target, where Amp f is the amplitude value of the f-th Doppler channel.

6. A strong ground object Doppler sidelobe suppression system based on window function frequency domain processing, characterized in that: include: Pulse compression module, used to obtain echo data of strong ground objects and perform pulse compression on the echo data; A Fourier transform module is used to perform Fourier transform on the window function added to the echo data after pulse compression to obtain a frequency domain window function; A sidelobe threshold coefficient calculation module is used to obtain the sidelobe threshold coefficient of each Doppler channel of all range units based on the frequency domain window function and the system noise average value; A sidelobe threshold value calculation module, used to obtain a sidelobe threshold value based on a sidelobe threshold value coefficient; The Doppler sidelobe suppression module is used to suppress the Doppler sidelobe based on the Doppler sidelobe threshold.

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