A matched filtering method for removing oblique echoes in linear and noisy composite FM radar

Abstract

The present invention discloses a matched filtering method for de-oblique echo of a linear and noise composite frequency modulation radar, and relates to the field of radar detection technology; the method comprises: the radar is a continuous wave system, sampling and receiving a de-oblique echo signal of a coherent processing interval (CPI), and selecting the noise frequency modulation signal component corresponding to the CPI in the radar transmission signal; conjugate multiplying the echoes of any two adjacent pulse repetition intervals (PRI) in the de-oblique echo signal to obtain a signal to be matched; similarly, conjugate multiplying the signals of the two PRIs corresponding to the noise frequency modulation signal component to obtain a reference signal; matching filtering is performed on the signal to be matched and the reference signal to obtain a one-dimensional range image of the target. The present invention improves the conventional matched filtering method, offsets the interference of the difference frequency signal phase in the de-oblique echo, makes it suitable for the linear and noise composite frequency modulation radar, and has good target ranging performance.

Description

Technical Field

[0001] The invention relates to the field of noise radar and radar signal processing, and in particular to a matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar. Background Art

[0002] Noise radar originated in the 1950s. It is a radar whose transmission signal is a random (noise, chaotic) waveform. Its transmission signal can be a directly generated noise source or a sinusoidal waveform modulated by random phase or frequency. Due to the randomness of the transmission signal, the noise radar has the characteristics of low interception, anti-interference, high electromagnetic compatibility and good electronic countermeasures; at the same time, the noise frequency modulation waveform has an ideal thumbtack fuzzy function, which gives the radar good detection performance. However, due to various conditions and limitations of software and hardware technology in the past, the development of noise radar has been slow and has not been well promoted and applied. In recent years, with the increasing requirements of high-tech warfare for radar anti-interference, and the rapid development of microwave and integrated circuit technology, the research on the system and application of noise radar has been continuously deepened and expanded.

[0003] Conventional noise frequency modulation radar matches the echo signal with the transmission signal and filters it to achieve optimal extraction and detection of the target signal through matching between the signals. However, in order to obtain better ranging and speed measurement performance and improve resolution, noise radar often needs to increase the bandwidth of the transmission signal, which results in the radar receiver requiring a higher A / D sampling rate to sample the echo.

[0004] The linear and noise composite FM radar performs de-skewing before sampling the echo A / D, which effectively reduces the bandwidth of the radar echo de-skewing signal and reduces the sampling rate requirement. However, the de-skewing process also introduces interference of the difference frequency signal phase to the de-skewing echo signal, making the conventional matched filtering method no longer effective. Summary of the invention

[0005] The object of the present invention is to provide a matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar, so as to solve the problem that the conventional matched filtering method is not suitable for removing oblique echoes of a linear and noise composite frequency modulation radar.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions: A matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar, comprising:

[0007] The radar is a continuous wave system. It samples and receives the de-slanted echo signal, performs conjugate multiplication processing on the signals of adjacent pulse repetition intervals contained therein, cancels the interference of the difference frequency signal phase, and obtains the signal to be matched.

[0008] Select the corresponding noise frequency modulation signal component in the radar transmission signal, perform conjugate multiplication processing on the signals of adjacent pulse repetition intervals contained in the signal component, and obtain a reference signal;

[0009] Matching filtering is performed on the above-mentioned signal to be matched and the reference signal to obtain a one-dimensional range image of the target.

[0010] Furthermore, the radar is a continuous wave system, sampling and receiving a de-slanted echo signal of a coherent processing interval (CPI), which can be expressed as:

[0011]

[0012] Among them: One CPI contains M pulse repetition intervals (PRI), , is the time width of the signal in each PRI, ; is a rectangular function, ; is the amplitude of the radar echo de-slanted signal, is the target delay, , is the target distance, is the speed of light; the difference frequency signal frequency , is a fixed coefficient, is the Doppler frequency, is a constant phase; is the noise frequency modulation phase of the i-th PRI de-slanted echo signal in the CPI, , modulation noise is a zero-mean, wide-sense stationary random process, is the time variable of the modulation noise, is the noise frequency modulation slope.

[0013] Furthermore, the noise frequency modulation signal component corresponding to CPI in the radar transmission signal is selected and expressed as:

[0014]

[0015] in, is the phase of the noise frequency modulation signal component in the i-th PRI of the radar transmission signal CPI corresponding to the de-oblique echo signal CPI. The noise frequency modulation phase of the i-th PRI de-oblique echo signal in step S1 is It is its time delay; is the amplitude of the noise FM signal component.

[0016] Furthermore, the de-slanted echo signal The signals of any two adjacent PRIs (i-th and i+1-th) are conjugate multiplied to cancel the interference of the difference frequency signal phase and obtain the signal to be matched of the i-th PRI, which is expressed as:

[0017]

[0018] in, , is the i-th PRI de-slanted echo signal, conj means to find the conjugate, .

[0019] Furthermore, the noise frequency modulation signal components of the radar transmission signal and the two adjacent PRIs (i-th and i+1-th) are conjugate multiplied to obtain the reference signal of the i-th PRI, which is expressed as:

[0020]

[0021] in, , is the noise frequency modulation signal component in the i-th PRI radar transmission signal, conj means to find the conjugate, .

[0022] Furthermore, the signal to be matched The corresponding reference signal Perform matched filtering to obtain the target one-dimensional range image of the i-th PRI, which is expressed as:

[0023]

[0024] Among them, FFT means Fourier transform, IFFT means inverse Fourier transform, conj means conjugate, The time delay information of the target can be obtained through the position of the narrow pulse function in the one-dimensional range image of the target.

[0025] Furthermore, the obtained M-1 PRI target one-dimensional distance image , , the data is rearranged into a matrix, That is the i-th row vector of the matrix, and finally the target one-dimensional distance image matrix of the entire CPI is obtained.

[0026] Compared with the prior art, the present invention has the following remarkable effects:

[0027] The present invention proposes a matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar, which improves the conventional matched filtering method, offsets the interference of the difference frequency signal phase in the linear and noise composite frequency modulation radar removing oblique echoes, and is suitable for the linear and noise composite frequency modulation radar. The linear and noise composite frequency modulation radar achieves the expected matched filtering effect while reducing the sampling rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention provides a flow chart of a matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar.

[0029] Figure 2 This is a simulation diagram of target ranging of linear and noise composite FM radar after matched filtering in an embodiment of the present invention, and is a one-dimensional image of the target range of the 129th PRI.

[0030] Figure 3 It is a three-dimensional image of the target ranging simulation of the linear and noise composite FM radar after matched filtering in the embodiment of the present invention, and it is a one-dimensional image matrix of the target distance of the entire CPI.

[0031] Figure 4 This is a distance-amplitude dimension view of a three-dimensional diagram of a linear and noise composite FM radar target ranging simulation after matched filtering in an embodiment of the present invention.

[0032] Figure 5 This is a range-Doppler dimension view of a three-dimensional image of a linear and noise composite FM radar target ranging simulation after matched filtering in an embodiment of the present invention.

[0033] Figure 6 This is a three-dimensional diagram of target ranging simulation of linear and noise composite FM radar after moving target detection in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0035] The present invention proposes a matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar. The method flow is as follows: Figure 1 As shown, specifically including:

[0036] S1: The radar is a continuous wave system, sampling and receiving de-slanted echo signals;

[0037] S2: Select the corresponding noise frequency modulation signal component in the radar transmission signal;

[0038] S3: Perform conjugate multiplication processing on the signals of adjacent pulse repetition intervals in the de-slanted echo signal received by S1 to offset the interference of the difference frequency signal phase and obtain the signal to be matched;

[0039] S4: Perform conjugate multiplication processing on the noise frequency modulation signal components of adjacent pulse repetition intervals in the S2 radar transmission signal to obtain a reference signal;

[0040] S5: Perform matched filtering on the signal to be matched obtained in S3 and the reference signal obtained in S4 to obtain a one-dimensional range image of the target.

[0041] In this embodiment, step S1 further includes:

[0042] The radar is a continuous wave system, sampling and receiving a de-slanted echo signal of a coherent processing interval (CPI), which can be expressed as:

[0043]

[0044] Among them: One CPI contains M pulse repetition intervals (PRI), , is the time width of each PRI signal, ; is a rectangular function, ; is the amplitude of the radar echo de-slant signal, t is the time variable, is the target delay, , is the target distance, is the speed of light; the difference frequency signal frequency , is a fixed coefficient, is the Doppler frequency, is a constant phase; is the noise frequency modulation phase of the i-th PRI de-slanted echo signal in the CPI, , modulation noise is a zero-mean, wide-sense stationary random process, is the noise frequency modulation slope.

[0045] In this embodiment, step S2 further includes:

[0046] The noise frequency modulation signal component corresponding to CPI in the radar transmission signal is selected and expressed as:

[0047]

[0048] in, is the phase of the noise frequency modulation signal component in the i-th PRI of the radar transmission signal CPI corresponding to the de-oblique echo signal CPI. The noise frequency modulation phase of the i-th PRI de-oblique echo signal in step S1 is It is its time delay; is the amplitude of the noise FM signal component.

[0049] In this embodiment, step S3 further includes:

[0050] De-slope echo signal The signals of any two adjacent PRIs (i-th and i+1-th) are conjugate multiplied to cancel the interference of the difference frequency signal phase and obtain the signal to be matched of the i-th PRI, which is expressed as:

[0051]

[0052] in, , is the i-th PRI de-slanted echo signal, conj means to find the conjugate, .

[0053] In this embodiment, step S4 further includes:

[0054] The noise frequency modulation signal components of the two PRIs (i-th and i+1-th) corresponding to step S3 in the radar transmission signal are conjugate multiplied to obtain the reference signal of the i-th PRI, which is expressed as:

[0055]

[0056] in, , is the noise frequency modulation signal component in the i-th PRI radar transmission signal, conj means to find the conjugate, .

[0057] In this embodiment, step S5 further includes:

[0058] Signal to be matched The corresponding reference signal Perform matched filtering to obtain the target one-dimensional range image of the i-th PRI, which is expressed as:

[0059]

[0060] Among them, FFT stands for Fourier transform, IFFT stands for inverse Fourier transform, and conj stands for conjugation. The time delay information of the target can be obtained by the position of the narrow pulse function in the one-dimensional range image of the target.

[0061] In this embodiment, step S5 further includes:

[0062] The method to obtain the one-dimensional range image of the entire CPI target is:

[0063] ,from arrive , repeat steps S3, S4, and S5 in sequence to obtain The target one-dimensional range image of each PRI is obtained by rearranging the data into a matrix, and taking the target one-dimensional range image data of each PRI as the matrix row vector. The target range image matrix of each row is the target one-dimensional range image of the entire CPI.

[0064] In the example of the present invention, the performance advantages of the present invention are illustrated by simulating the matched filtering method of removing oblique echoes of a linear and noise composite FM radar to measure the distance to the target. The parameter settings are shown in Table 1.

[0065] In the specific implementation process, the software platform is: Matlab simulation experiment platform.

[0066] Table 1

[0067]

[0068] Figure 2-Figure 6 The target ranging simulation results of the linear and noise composite FM radar are given from multiple angles. It can be clearly seen that the simulation results are consistent with the preset targets, indicating that the matched filtering method for removing oblique echoes of the linear and noise composite FM radar proposed in the present invention has good ranging performance and is suitable for the linear and noise composite FM radar, so that the linear and noise composite FM radar can achieve good matching filtering effect while reducing the sampling rate.

[0069] The above embodiments show and describe the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements. These changes and improvements all fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar, characterized in that: include: The radar is a continuous wave system. It samples and receives the de-slanted echo signal, performs conjugate multiplication processing on the signals of adjacent pulse repetition intervals contained therein, cancels the interference of the difference frequency signal phase, and obtains the signal to be matched. The sampled received CPI de-slanted echo signal is expressed as: ； Among them: one CPI contains M PRIs, , is the time width of the signal in each PRI, ; is a rectangular function, ; is the amplitude of the radar echo de-slanted signal, is the target delay, , is the target distance, is the speed of light; the difference frequency signal frequency , is a fixed coefficient, is the Doppler frequency, is a constant phase; is the noise frequency modulation phase of the i-th PRI de-slanted echo signal in the CPI, , modulation noise is a zero-mean, wide-sense stationary random process, is the time variable of the modulation noise, is the noise frequency modulation slope; Select the corresponding noise frequency modulation signal component in the radar transmission signal, perform conjugate multiplication processing on the signals of adjacent pulse repetition intervals contained in the signal component, and obtain a reference signal; The noise frequency modulation signal component corresponding to CPI in the radar transmission signal is selected and expressed as: ； in, is the phase of the noise frequency modulation signal component in the i-th PRI of the radar transmission signal CPI corresponding to the de-oblique echo signal CPI. The noise frequency modulation phase of the i-th PRI de-oblique echo signal in step S1 is It is its time delay; is the amplitude of the noise frequency modulation signal component; De-slope echo signal The signals of any two adjacent PRIs are conjugate-multiplied to cancel the interference of the difference frequency signal phase and obtain the signal to be matched of the i-th PRI, which is expressed as: ； in, , is the de-slanted echo signal of the i-th PRI, conj means to find the conjugate, ; The noise frequency modulation signal components of the radar transmission signal and the adjacent two PRIs are conjugate-multiplied to obtain the reference signal of the i-th PRI, which is expressed as: ； in, , is the noise frequency modulation signal component in the i-th PRI radar transmission signal, conj means to find the conjugate, ; Matching filtering is performed on the above-mentioned signal to be matched and the reference signal to obtain a one-dimensional range image of the target.

2. The matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar according to claim 1 is characterized in that: Signal to be matched The corresponding reference signal Perform matched filtering to obtain the target one-dimensional range image of the i-th PRI, which is expressed as: ； Among them, FFT means Fourier transform, IFFT means inverse Fourier transform, conj means conjugate, ; The time delay information of the target can be obtained through the position of the narrow pulse function in the one-dimensional range image of the target.

3. The matched filtering method for removing oblique echoes of a linear and noise composite frequency modulation radar according to claim 2 is characterized in that: The obtained M-1 PRI target one-dimensional distance image , , the data is rearranged into a matrix, That is the i-th row vector of the matrix, and finally the target one-dimensional distance image matrix of the entire CPI is obtained.

4. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method according to any one of claims 1 to 3 are implemented.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 3 are implemented.

6. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 3 are implemented.

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