High-Resolution Range Profile Simulation Method Based on Piecewise Periodic Modulation Signal

Abstract

The present application relates to a high-resolution range profile simulation method based on a segmented periodic modulation signal. The method includes: extracting target feature information of a one-dimensional high-resolution range profile of a target to be simulated, determining modulation parameters of the segmented periodic modulation signal according to the target feature information, generating a segmented periodic modulation signal based on the determined modulation parameters, modulating an incident signal on a phase modulation surface with the segmented periodic modulation signal to obtain a modulated echo signal of the phase modulation surface, and performing pulse compression processing on the modulated echo signal of the phase modulation surface to obtain a simulated one-dimensional high-resolution range profile of the target echo signal. Using this method can achieve a realistic simulation of the target HRRP.

Description

Technical Field

[0001] The present application relates to the technical field of radar signal processing, and particularly to a method for simulating high-resolution range profiles based on piecewise periodic modulation signals. Background Art

[0002] One-dimensional high-resolution range profile (HRRP) is the distribution of target scattering centers along the radar line of sight, which contains rich structural information such as target size and scatterer intensity, and is an important feature for radar target recognition. Radar target feature simulation technology can generate false features similar to real targets, effectively preventing the acquisition of real target information, and is one of the current important research directions.

[0003] In recent years, the emergence and development of electromagnetic modulation metamaterials have provided a new idea for simulating target HRRP. By precisely regulating the parameters of incident waves in real time, feature modulation of HRRP can be achieved, and it has the advantages of rapid response and low cost.

[0004] Existing research on target HRRP simulation is mainly based on active frequency selective surface (AFSS) and phase switched screen (PSS). Through time-domain periodic modulation of incident signals, a series of discrete peaks are generated in the range dimension. However, the false scatterers generated by these modulation methods are symmetrically and equally spaced about the center position of the metasurface, which is inconsistent with the complex structure of real targets and is easily recognized by broadband radar systems. Aiming at the deficiencies of current HRRP simulation methods, the present invention designs a piecewise periodic modulation signal based on a phase modulation metasurface, and designs signal modulation parameters based on the HRRP characteristics of the target, which can achieve a realistic simulation of the target HRRP. Summary of the Invention

[0005] Based on this, it is necessary to provide a method for simulating high-resolution range profiles based on piecewise periodic modulation signals that can realistically simulate target HRRP for the above technical problems.

[0006] A method for simulating high-resolution range profiles based on piecewise periodic modulation signals, the method comprising:

[0007] Obtain the target echo signal to be simulated, and extract target feature information according to the one-dimensional high-resolution range profile of the target echo signal;

[0008] Determine the modulation parameters of the piecewise periodic modulation signal according to the target feature information, and generate a piecewise periodic modulation signal based on the determined modulation parameters;

[0009] Modulate the incident signal on the phase modulation surface by using the segmented periodic modulation signal to obtain the echo signal modulated by the phase modulation surface;

[0010] Perform pulse compression processing on the echo signal modulated by the phase modulation surface to obtain the simulated one-dimensional high-resolution range profile of the target echo signal. In one embodiment, extract the number of discrete peaks, the position of each discrete peak, and the amplitude in the one-dimensional high-resolution range profile of the target echo signal, and use the number of discrete peaks, the positions and amplitudes of the discrete peaks as the target feature information.

[0011] In one embodiment, the modulation parameters include: the number of segments of the segmented periodic modulation signal, the modulation frequency, the duty cycle, and the duration.

[0012] In one embodiment, determining the modulation parameters of the segmented periodic modulation signal according to the target feature information includes:

[0013] Determine the number of segments according to the number of discrete peaks in the one-dimensional high-resolution range profile;

[0014] Align the positions of the -1 order false targets in each subsequence of the segmented periodic modulation signal with the positions of the corresponding target scattering points in the one-dimensional high-resolution range profile to determine the modulation frequency;

[0015] Align the normalized amplitudes of the -1 order false targets in each subsequence of the segmented periodic modulation signal with the normalized amplitudes of the corresponding target scattering points in the one-dimensional high-resolution range profile to determine the duration.

[0016] In one embodiment, the duty cycle is set to 0.5.

[0017] In one embodiment, to determine the modulation frequency, the following formula is used:

[0018] ;

[0019] In the above formula, represents the modulation frequency of the th subsequence, represents the chirp rate of the chirp signal, represents the speed of light, represents the distance between the th peak of the target and the radar, is the distance between the phase modulation surface and the radar.

[0020] In one embodiment, to determine the duration, the following formula is used:

[0021] ;

[0022] In the above formula, represents the duration of the sub - sequence segment, represents the scattering intensity of the target's th peak, and

[0023] represents the pulse width of the chirp signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic flow chart of a high - resolution range profile simulation method based on a segmented periodic modulation signal in an embodiment;

[0025] Figure 2 is a schematic time - domain diagram of a segmented periodic modulation signal in an embodiment;

[0026] Figure 3 is a schematic diagram of the simulation experimental results of target HRRP simulation in a simulation experiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] As Figure 1 shown, in the present application, a high - resolution range profile simulation method based on a segmented periodic modulation signal is provided, including the following steps:

[0029] Step S100, obtain the target echo signal to be simulated, and extract target feature information according to the one - dimensional high - resolution range profile of the target echo signal.

[0030] Step S110: Determine the modulation parameters of the segmented periodic modulation signal according to the target feature information, and generate a segmented periodic modulation signal based on the determined modulation parameters.

[0031] Step S120: Modulate the incident signal on the phase modulation surface with the segmented periodic modulation signal to obtain the echo signal modulated by the phase modulation surface.

[0032] Step S130: Perform pulse compression processing on the echo signal modulated by the phase modulation surface to obtain the simulated one-dimensional high-resolution range profile of the target echo signal.

[0033] In this application, a segmented periodic modulation signal based on a phase modulation metasurface is designed. Its number of segments, modulation frequency, and duration are determined by the number, position, and intensity of the target HRRP strong scattering points respectively. After pulse compression, an HRRP similar to the real target features can be generated.

[0034] First, introduce the segmented periodic modulation signal, the radar echo of the phase modulation surface and the one-dimensional high-resolution range profile, as well as the expression models of the radar echo and the one-dimensional high-resolution range profile of the target.

[0035] Different from the traditional periodic intermittent modulation signal, the modulation period of the segmented periodic modulation signal varies in segments and can be divided into sub-sequences according to different modulation frequencies. Its time-domain waveform is as Figure 2 shown. Denote the segmented periodic modulation signal as , the sub-sequence is , then the segmented periodic modulation signal is the sum of multiple sub-sequences, expressed as:

[0036] (1)

[0037] The radar echoes of the target and the phase modulation surface are respectively denoted as , , where the subscripts and respectively represent the data related to the target and the phase modulation surface. The corresponding HRRPs can be obtained by the radar performing pulse compression processing on the echoes, and are respectively denoted as , .

[0038] In this embodiment, the sub-sequence is defined as:

[0039] (2)

[0040] In formula (2), the duration of the sub-sequence is , the modulation period is , and the duty cycle is , represents convolution, is the window function, is the impulse function, is the number of pulses contained in the sub-sequence segment.

[0041] Then, perform Fourier transform on formula (2), and the expression of the sub-sequence in the frequency domain can be obtained as:

[0042] (3)

[0043] In formula (3), , is the sinc function, , .

[0044] In this embodiment, the radar echo signal of the phase modulation surface (PSS) is defined. The linear frequency modulation (LFM) signal is commonly used as the transmit signal of the imaging radar. The radar echo signal after being modulated by PSS is:

[0045] (4)

[0046] In formula (4), is the scattering intensity of PSS, is the distance from PSS to the radar, is the carrier frequency of LFM, is the frequency modulation slope of LFM, B is the bandwidth of LFM.

[0047] Further, define the one-dimensional high-resolution range profile of the phase modulation surface . The HRRP of PSS can be obtained by de-chirping the echo signal. First, set the reference signal as:

[0048] (5)

[0049] In formula (5), is the reference distance.

[0050] Then, multiply the conjugate of the echo signal of PSS with the reference signal , and remove the residual video phase, and the difference frequency output can be obtained as:

[0051] (6)

[0052] It can be seen from Equation (6) that the second phase term has nothing to do with the calculation of HRRP. Perform Fourier transform on Equation (6) and substitute the linear relationship between frequency and distance , then the one-dimensional high-resolution range profile of the phase modulation surface can be obtained, expressed as:

[0053] (7)

[0054] In Equation (7), is the distance variable, is the modulation frequency of the th subsequence. It can be known from Equation (7) that after PSS modulation, a series of discrete false peaks can be generated in the range direction. The position and amplitude of the th false peak corresponding to the th subsequence are respectively:

[0055] (8)

[0056] In this embodiment, the radar echo of the target is defined. Let the number of scatterers of the target be , the distance between the th scatterer and the radar be , and the scattering intensity be , then the target echo signal received by the radar is:

[0057] (9)

[0058] Furthermore, the one-dimensional high-resolution range profile of the target radar echo is defined. Multiply the echo signal of the target by the conjugate of the reference signal and remove the residual video phase, and the difference frequency output can be obtained as:

[0059] (10)

[0060] It can be seen from Equation (10) that the second phase term has nothing to do with the calculation of HRRP. Perform Fourier transform on Equation (10) and substitute the linear relationship between frequency and distance , and the one-dimensional high-resolution range profile of the target radar echo can be obtained, expressed as:

[0061] (11)

[0062] It can be obtained through Equation (11) that the position and amplitude of the th scatterer of the target on the HRRP are respectively:

[0063] (12)

[0064] In step S100, first, the number of discrete peaks, the position of each discrete peak, and the amplitude are extracted from the one-dimensional high-resolution range profile of the radar echo signal of the target to be simulated, and the number of discrete peaks, the positions and amplitudes of the discrete peaks are used as target feature information. Actually, the target feature information of the target to be simulated can be stored in advance and directly called during HRRP simulation.

[0065] In step S110, the modulation parameters of the segmented periodic modulation signal include: the number of segments of the segmented periodic modulation signal, the modulation frequency, the duty cycle, and the duration.

[0066] In this embodiment, determining the modulation parameters of the segmented periodic modulation signal according to the target feature information includes: determining the number of segments according to the number of discrete peaks in the one-dimensional high-resolution range profile. The modulation frequency is determined by aligning the positions of the false targets in each subsequence of the segmented periodic modulation signal with the positions of the corresponding target scattering points in the one-dimensional high-resolution range profile. The duration is determined by aligning the normalized amplitudes of the false targets in each subsequence of the segmented periodic modulation signal with the normalized amplitudes of the corresponding target scattering points in the one-dimensional high-resolution range profile.

[0067] In this embodiment, to achieve the blanking of PSS at the original position, the modulation duty cycle is fixed at 0.5. Considering that except for the 0th-order peak, the energy of the ±1st-order false targets of the interference is the largest, so the simulation of the target HRRP is realized based on the -1st-order false target, that is .

[0068] Specifically, it is set that the number of segments of the modulation signal is equal to the number of discrete peaks of the target HRRP, that is:

[0069] (13)

[0070] In formula (13), and are respectively the number of segments of the modulation signal and the number of discrete peaks of the target HRRP.

[0071] Specifically, the modulation frequency of each subsequence is set so that the -1st-order false target of the th subsequence is aligned with the position of the th scattering point of the target, that is:

[0072] (14)

[0073] Substituting formula (14) into formulas (8) and (12), the formula for calculating the modulation frequency is obtained, expressed as:

[0074] (15)

[0075] In formula (15), represents the modulation frequency of the th sub-sequence, represents the frequency modulation slope of the chirp signal, represents the speed of light, represents the distance between the th peak of the target and the radar, is the distance between the phase modulation surface and the radar.

[0076] Specifically, set the duration of each sub-sequence so that the -1 order false target of the th sub-sequence has the same normalized amplitude as the HRRP corresponding to the th scattering point of the target, that is:

[0077] (16)

[0078] Similarly, substituting formula (16) into formulas (8) and (12), the formula for calculating the duration is obtained, which is expressed as:

[0079] (17)

[0080] In formula (17), represents the duration of the th sub-sequence, represents the scattering intensity of the th peak of the target, represents the pulse width of the chirp signal.

[0081] Furthermore, after determining the number of segments, modulation frequency, duty cycle, and duration of the segmented periodic modulation signal, the segmented periodic modulation signal can be generated.

[0082] In step S120, the incident signal on the phase modulation surface is modulated by the segmented periodic modulation signal to obtain the phase-modulated signal.

[0083] In step S130, after performing pulse compression processing on the echo signal modulated by the phase modulation surface, the simulated HRRP of the target can be obtained.

[0084] In this article, the effectiveness of this method is also demonstrated through simulation experiments. Experimental scenario and radar parameter settings: Set a target with three strong scattering points for simulation experiments, with distances of 5m, 10m, and 13m respectively, and the scattering intensities are all 1. The phase modulation surface is located at 0m, and the scattering intensity is 2. The carrier frequency of the radar transmitting LFM signal is 10GHz, the pulse width is 100us, and the bandwidth is 1GHz.

[0085] Signal parameter setting: The modulation signal is divided into three sub - sequences. The duration of the first sub - sequence is 20 us, and the modulation frequency is 555.56 KHz; the duration of the second sub - sequence is 20 us, and the modulation frequency is 1.11 MHz; the duration of the third sub - sequence is 20 us, and the modulation frequency is 1.444 MHz.

[0086] The results of the simulation experiment are shown in Figure 3 . Figure 3 In it, the solid line and the dashed line are the HRRP of the target and the HRRP of the phase - modulation surface respectively. It can be seen from the figure that after modulation, three - 1st - order false peaks are generated on the phase - modulation surface, and their positions and amplitudes are highly consistent with the three discrete peaks in the target HRRP, which proves the effectiveness of this method.

[0087] In the above - mentioned high - resolution range profile simulation method based on the segmented periodic modulation signal, by extracting the target feature information of the one - dimensional high - resolution range profile of the target to be simulated, determining the modulation parameters of the segmented periodic modulation signal according to the target feature information, generating the segmented periodic modulation signal based on the determined modulation parameters, modulating the incident signal on the phase - modulation surface with the segmented periodic modulation signal to obtain the phase - modulation signal, and performing pulse compression processing on the phase - modulation signal to obtain the simulated one - dimensional high - resolution range profile of the target echo signal. Compared with the traditional periodic modulation signal, the designed segmented periodic modulation signal in this method can generate a series of irregularly distributed false images, and the modulation pattern is more flexible and changeable. By extracting the number and amplitude of the target HRRP peaks, this method can achieve a realistic simulation of the target HRRP based on a phase - modulation surface, with advantages such as high cost - effectiveness and simple parameter calculation.

[0088] It should be understood that although Figure 1 the steps in the flowchart of Figure 1 are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise clearly stated in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover,

[0089] at least a part of the steps in can include multiple sub - steps or multiple stages. These sub - steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub - steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub - steps or stages of other steps.

[0089] The technical features of the above - mentioned embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above - mentioned embodiments are described. However, as long as the combination of these technical features does not conflict, it should be considered as the scope described in this specification.

[0090] The above-described embodiments merely represent one implementation mode of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A high-resolution range profile simulation method based on segmented periodic modulation signal, characterized in that: The method comprises: Acquire a target echo signal to be simulated, and extract target feature information according to a one-dimensional high-resolution range image of the target echo signal; Determine the modulation parameters of the segmented periodic modulation signal according to the target characteristic information, and generate the segmented periodic modulation signal based on the determined modulation parameters, wherein determining the modulation parameters of the segmented periodic modulation signal according to the target characteristic information includes: determining the number of segments according to the number of discrete peaks in the one-dimensional high-resolution range image, determining the modulation frequency by aligning the positions of the -1 order false targets in each subsequence in the segmented periodic modulation signal with the positions of the corresponding target scattering points in the one-dimensional high-resolution range image, and determining the duration by aligning the normalized amplitude of the -1 order false targets in each subsequence in the segmented periodic modulation signal with the normalized amplitude of the corresponding target scattering points in the one-dimensional high-resolution range image; Using the segmented periodic modulation signal to modulate the incident signal of the phase modulation surface, to obtain an echo signal modulated by the phase modulation surface; The echo signal modulated by the phase modulation surface is subjected to pulse compression processing to obtain a simulated one-dimensional high-resolution range image of the target echo signal.

2. The high-resolution range profile simulation method based on segmented periodic modulation signal according to claim 1, characterized in that: The number of discrete peaks, the position of each discrete peak, and the amplitude are extracted from the one-dimensional high-resolution range image of the target echo signal, and the number of discrete peaks, the position and amplitude of each discrete peak are used as the target feature information.

3. The high-resolution range profile simulation method based on segmented periodic modulation signal according to claim 2, characterized in that: The modulation parameters include: the number of segments, modulation frequency, duty cycle and duration of the segmented periodic modulation signal.

4. The high-resolution range profile simulation method based on segmented periodic modulation signal according to claim 3 is characterized in that: The duty cycle is set to 0.

5.

5. The high-resolution range profile simulation method based on segmented periodic modulation signal according to claim 3, characterized in that: To determine the modulation frequency, the following formula is used: In the above formula, Indicates The modulation frequency of the segment sequence, represents the frequency modulation slope of the linear frequency modulation signal, represents the speed of light, Indicates the target The distance between the peak and the radar, is the distance between the phase modulation surface and the radar.

6. The high-resolution range profile simulation method based on segmented periodic modulation signal according to claim 3, characterized in that: To determine the duration, use the following formula: In the above formula, Indicates The duration of the segment sequence, Indicates the target The peak scattering intensity is Indicates the pulse width of the linear frequency modulation signal.

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