Shield effect evaluation method and system based on shield pulse interference modulation waveform

Abstract

The invention discloses a shield effect evaluation method and system based on a shield pulse interference modulation waveform, and mainly solves the problems that the convergence speed is low and occasions with high real-time requirements are difficult to meet when an existing shield signal shields a radar. According to the implementation scheme, the method comprises the steps of solving a multi-factor objective function based on the cross-correlation sidelobe level of a radar signal and a shield signal through an SQP algorithm, solving the objective function to obtain an optimized shield signal, calculating the cross-correlation sidelobe level of the shield signal and a radar and the cross-correlation sidelobe level of the shield signal and a reconnaissance signal respectively, and calculating the cross-correlation sidelobe level of the shield signal and the reconnaissance signal. And fitting is carried out to obtain a mean value and a standard deviation of normal distribution, a shield effect evaluation criterion is constructed, and an evaluation result of whether shield succeeds or not is obtained. According to the method, the convergence speed can be increased, the global optimal solution can be effectively approached, the real-time requirement can be met, the comprehensive optimization capability of key indexes such as waveform sidelobe level can be expanded, the shield signal can be accurately evaluated, and the method can be used for electronic countermeasure.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and in particular relates to a shielding effect evaluation method and system that can be used for electronic countermeasures. Background Art

[0002] A masking signal is a signal used to interfere with or deceive a radar system. The research on masking signal masking radar has always been a hot topic in the military and civilian fields, with the goal of improving the radar system's anti-interference and countermeasure capabilities.

[0003] The existing MIMO radar background shield waveform design methods mainly include: (1) waveform design method based on fixed code type. The design process is relatively simple, but due to the fixed code type, its flexibility is poor and the cross-correlation performance of the waveform is limited; (2) waveform design method based on genetic algorithm. By simulating the inheritance, mutation and selection operations in the biological evolution process, the waveform parameters are searched and optimized. It is a global optimization algorithm, but it has the problems of high computational complexity and premature convergence; (3) waveform design method based on gradient descent method. The waveform parameters are updated using the gradient information of the objective function on the waveform parameters. However, this method is sensitive to the initial value and easily falls into the local optimum, which limits the further improvement of waveform performance.

[0004] In his published paper "A Phase Domain Low-Integral Sidelobe Radar Waveform Optimization Method" (724th Institute of China Shipbuilding Industry Corporation, published in the Journal of Radars in 2022), Wang Xinhai directly transformed the problem of solving the constant modulus sequence into the problem of solving the waveform phase sequence, and used the closed-form solution to iteratively update the waveform sequence. This method can reduce the sidelobe level to a certain extent, but the convergence speed is slow and requires a large number of iterative calculations. It cannot meet the occasions with high real-time requirements, and it is easy to fall into the local optimal solution, making it difficult to ensure the global optimal waveform.

[0005] In his paper "Research on Pulse Ultra-Wideband Communication Waveform Design for Space Formation Flying Vehicles" (Master's thesis at Harbin Institute of Technology in 2014), Xu Lei used the characteristics of orthogonal polynomials to construct pulse waveforms and used genetic algorithms to optimize the relevant parameters of the waveforms. Although this method can obtain waveforms with good cross-correlation characteristics and improve spectrum utilization, its ability to comprehensively optimize the sidelobe level and other key indicators of the waveform is limited, and its scope of application is narrow and the application scenarios are single, making it difficult to directly transplant it to fields such as radar detection and electronic countermeasures. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a shielding effectiveness evaluation method and system to improve the convergence speed and effectively approach the global optimal solution, meet the needs of occasions with high real-time requirements, and expand the comprehensive optimization capabilities of the waveform sidelobe level and other key indicators.

[0007] The technical solutions to achieve the above objectives include:

[0008] 1. A method for evaluating shielding effectiveness based on shielding pulse interference modulation waveform, comprising:

[0009] The SQP algorithm is used to construct an objective function based on multiple factors of the cross-correlation sidelobe level (PSL) between the radar signal and the cover signal:

[0010]

[0011] Where [e] = e b1 ,e b2 For, e b1 represents the cross-correlation sidelobe level of the shield signal and the radar signal, e b2 represents the cross-correlation sidelobe level of the cover signal and the reconnaissance signal; w represents the weight assigned to [e].

[0012] Solve the objective function y ∞ (s M ), and obtain the optimized cover signal S Mp ;

[0013] Calculate S separately Mp The cross-correlation sidelobe level PSL1 with the radar signal and the cross-correlation sidelobe level PSL2 with the reconnaissance signal;

[0014] Calculate the autocorrelation sidelobe level PSL3 of the radar signal and the pulse compression result y of the noisy radar signal Rn The maximum side lobe value is obtained and a histogram is fitted. The mean of the normal distribution is μ and the standard deviation is σ.

[0015] According to the maximum side lobe value PSL1 1max and the sidelobe maximum value PSL3 3max Define the cover success rate α, threshold T and judgment conditions, and use them to analyze the cover signal S Mp To conduct an assessment:

[0016] If 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ, the cover is successful, calculate the cover success rate α and evaluate the cover effect;

[0017] Otherwise, the cover fails and the cover signal S is re-optimized Mp and evaluate the effectiveness of cover.

[0018] 2. A shielding effect evaluation system based on a shielding pulse interference modulation waveform, characterized by comprising:

[0019] Signal definition module, used to define various signal models;

[0020] Signal modeling module, used to build a mathematical model of the signal;

[0021] Signal optimization module, used to optimize the shield signal S Mp Optimize

[0022] Sidelobe calculation module, used to calculate the cross-correlation sidelobe levels between various signals;

[0023] The shield parameter module is used to define shield effect evaluation parameters;

[0024] The shield evaluation module is used to evaluate the shield effect of shield signals.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] First, the present invention is based on the signal vector space operation rules, comprehensively considers the frequency, phase and spatial distribution characteristics of different signals, redefines the cross-correlation sidelobes, simplifies the calculation process, can accurately quantify the sidelobe level in complex signal environments, expand the sidelobe level of the waveform and the comprehensive optimization capabilities under key indicators such as frequency, phase and space, and improve the system's anti-interference performance.

[0027] Secondly, the present invention designs the objective function y based on the evaluation criteria of signal sidelobe suppression and signal shielding effectiveness in radar signal processing. ∞ (s M ), suppresses the cross-correlation sidelobe levels of radar signals and cover signals and increases the cross-correlation sidelobe levels of radar signals and reconnaissance signals to improve the cover effect, effectively enhances the adaptability of interference waveforms to multiple types of signals, improves the comprehensiveness and pertinence of cover effects in complex scenarios, and provides a better framework for the design of cover pulse interference modulation waveforms.

[0028] Third, based on the sequential quadratic programming (SQP) algorithm, the present invention transforms the problem of solving the objective function into a series of quadratic programming sub-problems with constraints for iterative solution. The gradient of the objective function and the constraints and the Hessian matrix are used to dynamically determine the optimal search direction that satisfies the constraints, and the global convergence of the iterative process is guaranteed by linear search or trust region strategy. At the same time, with the help of Hessian matrix update, the curvature of the objective function is efficiently approximated, so that the iteration can be rapidly advanced along the optimal direction in the feasible domain and meet the KTT condition. The global optimization capability is enhanced by coordinating the multi-starting point initialization strategy, so that the present invention can effectively approximate the global optimal solution while improving the convergence speed.

[0029] Fourthly, the present invention calculates the cross-correlation sidelobe levels of the radar signal, the cover signal, and the reconnaissance signal based on a redefined cross-correlation sidelobe calculation method, which can reduce the computational complexity. The use of the SQP algorithm to optimize the cover signal can reduce the computational time. The combination of the two can not only ensure a significant improvement in computing efficiency while optimizing accuracy, but also better meet the demand for fast processing in situations with high real-time requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a signal model diagram used in the present invention;

[0031] Figure 2 This is a flow chart of the method for evaluating the shielding effect of the shielding pulse interference modulation waveform of the present invention;

[0032] Figure 3 is the radar signal and cover signal directional pattern used in the present invention;

[0033] Figure 4 This is a structural block diagram of the shielding effect evaluation system of the shielding pulse interference modulation waveform of the present invention;

[0034] Figure 5 It is a time-frequency diagram of each signal simulated by the present invention;

[0035] Figure 6 The invention is used to simulate the cross-correlation sidelobe level diagram between various signals;

[0036] Figure 7 It is the amplitude distribution histogram and fitting curve of the pulse pressure signal simulated by the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] It should be noted that the step numbers in the specification and claims of the present invention are only for the purpose of clearly describing the embodiments of the present invention and facilitating understanding, and the order of the step numbers is not limited.

[0039] The implementation of the present invention is based on the fact that in the considered cover system model, the radar transmitter and the electronic protection EP equipment operate synchronously, and its signal model includes radar signal, cover signal, and reconnaissance signal, such as Figure 1As shown in Figure 1, the EP device can transmit a masking signal to mask the radar signal and interfere with the reconnaissance signal. To achieve better masking performance, the masking signal usually occupies a longer duration and a wider frequency range than the actual radar waveform.

[0040] Example 1: Shielding effect evaluation method based on shielding pulse interference modulation waveform

[0041] Reference Figure 2 The implementation steps of this example include the following:

[0042] Step 1: Design each signal in the signal model.

[0043] 1.1) Radar Signal

[0044] Assume that the multiple-input multiple-output MIMO radar transmitting array consists of N t The radar signal is a phase-coded signal, which is composed of N transmitting / receiving antennas. s chips, the radar signal Defined as:

[0045]

[0046] where N s is the number of signal chips, N t is the number of transmitting / receiving antennas, f0 is the signal center frequency, T0 is the signal chip width, n is the nth transmitting / receiving antenna, s(k) is the phase coded signal of the kth chip, is a rectangular window function;

[0047] 1.2) Cover signal

[0048] The cover signal refers to the signal for covering the radar, which is in the form of phase coding. The cover signal s is converted into a signal according to the phase coding signal, the number of signal chips, the signal center frequency, and the signal chip width. M Defined as:

[0049]

[0050] where s m (k) is the phase coded signal of the kth chip, N s is the number of signal chips, f m is the signal center frequency, T m is the signal chip width, s m (k) represents the phase coded signal of the kth chip, s M (t) is the phase encoding signal at time t;

[0051] 1.3) Radar signal weighted by steering vector

[0052] The direction of radar signals and cover signals, such as Figure 3 As shown, during the transmission process, the radar signal s R The emission angle θ2 is randomly changed, covering the signal s M The transmission angle θ1 is fixed. There is a transmission angle difference θ=θ2-θ1 between the radar signal and the cover signal. Therefore, the radar signal needs to be realized with the help of the antenna's steering vector. The steering vector a(θ) is expressed as:

[0053]

[0054] Where d is the array element spacing, λ = c / f0 is the radar signal wavelength, c is the speed of light, [] T is transposed;

[0055] According to the steering vector a(θ), the radar signal s R Redefine the radar signal s weighted by the steering vector Ra :

[0056] s Ra =a(θ)s R ;

[0057] 1.4) Reconnaissance Signal

[0058] The reconnaissance signal is a signal used to intercept and analyze radar signal parameters and provide information support for interference. It is expressed in the form of a linear frequency modulation signal. The reconnaissance signal s is defined according to the signal bandwidth, signal time width, and carrier frequency of the linear frequency modulation signal. R0 The expression is:

[0059] s R0 (t) = exp(j2πf R0 t+jπμt 2 )

[0060] Where μ = B / T is the frequency modulation slope, B is the signal bandwidth, T is the signal time width, f R0 is the carrier frequency of the transmitted signal, s R0 (t) is the linear frequency modulation signal at time t.

[0061] Step 2: Construct a mathematical model of the cover signal.

[0062] Based on the evaluation criteria of signal sidelobe suppression and signal mask effectiveness in radar signal processing, this method suppresses the radar signal s Ra With cover signals M The cross-correlation sidelobe level PSL between the shield signal and the reconnaissance signal s R0The PSL of the signal is used to improve the interference capability, but the traditional cross-correlation sidelobe algorithm is difficult to meet the system's stringent requirements for signal interference suppression and detection accuracy. Therefore, based on the signal vector space operation rules, it is necessary to comprehensively consider the different signal frequencies, phases and spatial distribution characteristics and rebuild the signal mathematical model.

[0063] 2.1) Transform the radar signal s Ra With cover signals M The cross-correlation sidelobes of are redefined as r:

[0064] r={r k (f d )|,k∈K,f d ∈F d}

[0065] in, r k (f d ) indicates that the Doppler frequency shift is f d , the cross-correlation sidelobe level when the number of cycle steps is k, δ r is the error tolerance parameter of the cross-correlation sidelobe, f d0 is the Doppler shift of the radar signal, is the Doppler frequency shift matrix, diag(a d (f)) is to generate the Doppler frequency shift diagonal matrix, J k is the circulant transfer matrix, [] H is the conjugate transpose; K is the index set of the loop step number k, F d is the Doppler frequency shift f d The value set of , {} is a set operation;

[0066] 2.2) Based on the cross-correlation sidelobe r defined above, the cover signal is modeled as follows:

[0067]

[0068] Among them, f ∞ (s M ) indicates that s M The related function f takes the infinite norm, is the phase adjustment set of the cover signal, Θ is the value set of angle θ0, || || ∞ is the infinite norm;

[0069] Step 3: Construct the objective function based on the above mathematical model and use the sequential quadratic programming (SQP) algorithm to solve the objective function to obtain the optimized cover signal S Mp .

[0070] 3.1) Based on the cross-correlation sidelobe r defined above, the shielding signal s is obtained MWith radar signals Ra The cross-correlation sidelobe level e b1 and cover signals M With reconnaissance signals R0 The cross-correlation sidelobe level e b2 :

[0071]

[0072] Where f0 is the center frequency of the radar signal, f m is the center frequency of the cover signal;

[0073] 3.2) Let [e] = e b1 ,e b2 , considering the cover signal to achieve the cover and interference functions, the following objective function y is obtained ∞ (s M ):

[0074]

[0075] Where w represents the weight assigned to [e];

[0076] 3.3) Use the sequential quadratic programming (SQP) algorithm to solve the above objective function y ∞ (s M ):

[0077] 3.3.1) Set the number of loops K and the minimum value y of the objective function ∞ (s M )=+∞, current loop number k=1;

[0078] 3.3.2) Determine whether k≤K holds:

[0079] If so, the sequential quadratic programming algorithm is used to optimize the cross-correlation sidelobe level of the kth cycle |r k |, proceed to step 3.3.3);

[0080] Otherwise, return to step 3.3.1) and optimize again;

[0081] 3.3.3) Judgment k |<y ∞ (s M ) is established:

[0082] If so, let y ∞ (s M )=|r k |, and set k = k + 1, and return to step 3.3.2);

[0083] Otherwise, end the loop and get the optimized objective function y ∞ (sM ) and cover signal s M , execute step 3.3.4);

[0084] 3.3.4) The optimized cover signal s M Expressed as where N m is the number of chips of the cover signal, Represents a complex set.

[0085] Step 4: Based on the optimized cover signal S Mp , calculate the sidelobe level and pulse compression signal of radar signal and cover signal.

[0086] 4.1) Based on the optimized cover signal S Mp and its center frequency is f m , radar signal s Ra With its center frequency as f0, the cross-correlation sidelobe level PSL1 between the shield signal and the radar signal is calculated as:

[0087]

[0088] 4.2) Assume that the reconnaissance signal s R0 The center frequency is 0, and the cross-correlation sidelobe level PSL2 of the cover signal and the reconnaissance signal is calculated:

[0089]

[0090] 4.3) Calculate the autocorrelation sidelobe level PSL3 of the radar signal:

[0091]

[0092] 4.4) According to the above radar signal s Ra and the noise n it carries, forming a combined signal s Rn :

[0093] s Rn =s Ra +n,

[0094] in, n i,j is the Gaussian white noise sampling point signal of the i-th group and the j-th group, i=1,2,...10000, j=1,2,...N t ;

[0095] 4.5) Combine the signal s Rn Perform self-pulse pressure processing to obtain the pulse pressure signal y Rn for:

[0096]

[0097] in is the convolution operation.

[0098] Step 5: Fit the histogram distribution of the pulse pressure signal amplitude based on the function provided by the software, and set parameters such as the protection success rate and judgment conditions.

[0099] 5.1) Based on the above pulse pressure signal y Rn , calculate the sidelobe maximum value PSL of 10000 groups of combined signals 4max :

[0100]

[0101] 5.2) Based on the normal fitting function of the software, PSL 4max Perform histogram fitting, record the mean of the normal distribution obtained after fitting as μ, the standard deviation as σ, and draw the fitting curve;

[0102] 5.3) According to the sidelobe maximum value PSL of the cross-correlation sidelobe level PSL1 of the radar signal and the shield signal 1max , radar signal autocorrelation sidelobe level PSL3 sidelobe maximum value PSL 3max Based on the evaluation criteria for signal sidelobe suppression and signal shielding effectiveness in radar signal processing, the threshold T, shielding success rate α and judgment conditions are set as follows:

[0103] T=1 / μ,

[0104]

[0105] Judgment condition: 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ.

[0106] Step 6: Based on the parameters defined above, conduct an assessment of the shielding effectiveness.

[0107] Judgment 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ:

[0108] If so, the cover is successful. Calculate the cover success rate α and evaluate the cover effect. The larger α is, the better the cover effect is, and the smaller α is, the worse the cover effect is.

[0109] Otherwise, the cover fails and the cover signal S is re-optimized Mp and evaluate the effectiveness of cover.

[0110] Example 2: Guard Effect Evaluation System Based on Guard Pulse Interference Modulation Waveform

[0111] Reference Figure 4This example includes: a signal definition module 1, a signal modeling module 2, a signal optimization module 3, a sidelobe calculation module 4, a cover parameter module 5, and a cover evaluation module 6. The signal optimization module 3 includes: an objective function construction submodule 31 and an algorithm optimization solution submodule 32; the sidelobe calculation module 4 includes: a cover signal submodule 41, a radar signal submodule 42, and a combined signal submodule 43.

[0112] The whole system works as follows:

[0113] The signal definition module 1 is used to define various signal models, that is, to define radar signals, reconnaissance signals and cover signals based on the signal model of cover pulse interference modulation, and transmit the definition results to the signal modeling module;

[0114] The signal modeling module 2 is used to construct a mathematical model of the cover pulse interference modulation according to the defined cover signal, and transmit the mathematical model to the signal optimization module;

[0115] The signal optimization module 3 is used to optimize the shield signal S according to the established mathematical model. Mp Optimization is performed, i.e., the objective function of the cover signal is constructed by the objective function construction submodule 31; the objective function is solved by the algorithm optimization solution submodule 32 using the SQP algorithm to obtain the optimized cover signal, and the optimized cover signal is transmitted to the sidelobe calculation module;

[0116] The sidelobe calculation module 4 is used to calculate the cross-correlation sidelobe levels between various signals based on the optimized cover signal, that is, the cover signal submodule 41 calculates the optimized cover signal S Mp The radar signal submodule 42 calculates the autocorrelation sidelobe level PSL3 of the radar signal, and the combined signal submodule 43 calculates the autopulse pressure result y of the combined signal. Rn and transmit the above-mentioned cross-correlation sidelobe level results to the shield parameter module;

[0117] The shield parameter module 5 is used to define shield effect evaluation parameters according to the cross-correlation sidelobe level results and the signal sidelobe suppression and signal shield effectiveness evaluation criteria in radar signal processing, and transmit the shield effect evaluation parameters to the shield evaluation module;

[0118] The cover evaluation module 6 is configured to evaluate the cover effect of the cover signal according to the cover effect evaluation parameters, that is, to evaluate the effect of the cover signal according to the cover effect evaluation parameters.

[0119] The effects of the present invention can be further illustrated by the following simulation results:

[0120] 1. Simulation conditions

[0121] Parameter setting: MIMO transmit array consists of N t = 10 transmitting / receiving antennas, number of transmitted radar signal chips N s =128, radar signal s Ra The center frequency f0 = 1.5GHz, the chip width T0 = 20us; the cover signal s M The center frequency f m =2.13GHz, chip width T m =10us; reconnaissance signal s R0 The bandwidth B = 5MHz, the time width T = 20us, and the frequency modulation slope μ = B / T = 2.5×10 11 , carrier frequency f R0 =1.25GHz, N m =2, emission angle difference θ=0.

[0122] 2. Simulation content

[0123] Simulation 1: Based on the above simulation conditions, the time-frequency distribution of radar signals, cover signals and reconnaissance signals is simulated by the present invention. The results are as follows: Figure 5 As shown. Figure 5 a is the time domain diagram, Figure 5 b is the frequency domain diagram. Figure 5 and Figure 1 From the comparison of the signal models shown, it can be seen that the time characteristics of each signal obtained by the present invention are consistent with the time distribution of each signal in the signal model, and the frequency characteristics are consistent with the frequency position of each signal in the signal model, which verifies the rationality and accuracy of the method of the present invention.

[0124] Simulation 2, based on the above simulation conditions, the sidelobe levels between the radar signal, the cover signal and the reconnaissance signal are simulated by the present invention, and the results are as follows: Figure 6 As shown, the dashed star line is the autocorrelation sidelobe level PSL3 of the radar signal, the solid line is the cross-correlation sidelobe level PSL1 between the optimized cover signal and the radar signal, and the dashed plus line is the cross-correlation sidelobe level PSL2 between the optimized cover signal and the reconnaissance signal. Figure 6 It can be seen that PSL1 is reduced to -90dB and PSL2 ranges from -20 to -50dB. This shows that the optimized cover signal can reduce the cross-correlation sidelobe level with the radar signal to achieve effective cover while also better achieving cover performance by interfering with the reconnaissance signal.

[0125] Simulation 3, based on the above simulation conditions and the normal fitting function of the simulation software, the pulse pressure signal y is simulated by the present invention. Rn The distribution histogram and fitting results are as follows Figure 7As shown, the histogram is the maximum value of the side lobe of the pulse pressure signal PSL 4max The solid line is the normal fitting curve. Figure 7 It can be seen that PSL 4max It obeys the normal distribution, and the mean μ = 0.1433 and the standard deviation σ = 0.0043 of the fitted distribution are directly obtained through function calculation. The parameters are automatically output by the software algorithm without manual intervention.

[0126] Combining the results of simulation 2 and simulation 3, in order to evaluate the shielding effect of the shielding signal, the maximum sidelobe level PSL1 of the cross-correlation sidelobe level PSL1 of the radar signal and the shielding signal is directly obtained by function calculation. 1max =0.2008, the maximum sidelobe level PSL3 of the radar signal autocorrelation sidelobe level PSL 3max =0.0295, respectively calculate the threshold T, the cover success rate α is:

[0127] T=1 / μ=0.9784

[0128]

[0129] Based on the above parameters, refer to the evaluation method in step 6 to evaluate the cover effect, and meet the judgment condition 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ, which means that the shielding signal is successfully shielded, and the shielding success rate α=85.3%, which meets the design requirements.

Claims

1. A shielding effect evaluation method based on shielding pulse interference modulation waveform, characterized in that: include: The SQP algorithm is used to construct an objective function based on multiple factors of the cross-correlation sidelobe level (PSL) between the radar signal and the cover signal: Where [e] = e b1 ,e b2 For, e b1 represents the cross-correlation sidelobe level of the shield signal and the radar signal, e b2 represents the cross-correlation sidelobe level of the cover signal and the reconnaissance signal; w represents the weight assigned to [e]. Solve the objective function y ∞ (s M ), and obtain the optimized cover signal S Mp ; Calculate S separately Mp The cross-correlation sidelobe level PSL1 with the radar signal and the cross-correlation sidelobe level PSL2 with the reconnaissance signal; Calculate the autocorrelation sidelobe level PSL3 of the radar signal and the pulse compression result y of the noisy radar signal Rn The maximum side lobe value is obtained and a histogram is fitted. The mean of the normal distribution is μ and the standard deviation is σ. According to the maximum side lobe value PSL1 1max and the sidelobe maximum value PSL3 3max The cover success rate α, threshold T and judgment conditions are used to analyze the cover signal S Mp To conduct an assessment: If 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ, the cover is successful, calculate the cover success rate α and evaluate the cover effect; Otherwise, the cover fails and the cover signal S is re-optimized Mp and evaluate the effectiveness of cover.

2. The method according to claim 1, characterized in that The SQP algorithm is used to construct an objective function based on multiple factors of the cross-correlation sidelobe level PSL of the radar signal and the cover, and its implementation includes: 2a) Assume radar signal The phase encoding form is: where N s is the number of signal chips, N t is the number of transmitting / receiving antennas, f0 is the signal center frequency, T0 is the signal chip width, n is the nth transmitting / receiving antenna, s(k) is the phase coded signal of the kth chip, is a rectangular window function; 2b) The shield signal s M It is expressed as a phase-coded signal: where f m is the signal center frequency, T m is the signal chip width, s m (k) represents the phase coded signal of the kth chip, s M (t) is the phase encoding signal at time t; 2c) Calculate the above radar signal s R With cover signals M The transmission angle difference θ = θ2 - θ1, where θ2 is the randomly changing radar signal transmission angle and θ1 is the fixed angle of the cover signal transmission angle. The radar signal needs to be realized with the help of the antenna's steering vector, which is expressed as: 2d) Based on the transmission angle difference between the two signals, the steering vector a(θ) of the radar signal is expressed as: Where d is the array element spacing, λ = c / f0 is the radar signal wavelength, c is the speed of light, [] T is transposed; According to the steering vector a(θ), the radar signal is re-expressed as s Ra : s Ra =a(θ)s R ; 2e) Based on the signal vector space operation rules, considering the frequency, phase and spatial distribution characteristics of different signals, the re-expressed radar signal s is defined Ra With cover signals M The cross-correlation side lobe r of r={r k (f d )|,k∈K,f d ∈F d } in, Indicates that the Doppler frequency shift is f d , the cross-correlation sidelobe level when the number of cycle steps is k, δ r is the error tolerance parameter of the cross-correlation sidelobe, f d0 is the Doppler shift of the radar signal, is the Doppler frequency shift matrix, diag() is to generate a diagonal matrix, J k is the circulant transfer matrix, [] H is the conjugate transpose; f ∞ (s M ) indicates that s M The related function f takes the infinite norm, is the phase adjustment set of the cover signal, K is the index set of the cycle step number k, F d is the Doppler frequency shift f d The value set of θ is the value set of angle θ0, |||| ∞ is the infinite norm, {} is the set operation; 2f) Based on the above cross-correlation sidelobe definition, we can get the shielding signal s M With radar signals Ra The cross-correlation sidelobe level e b1 and cover signals M With reconnaissance signals R0 The cross-correlation sidelobe level e b2 : Where f0 is the center frequency of the radar signal, f m is the center frequency of the cover signal; 2g) Let [e] = e b1 ,e b2 , we get the following objective function y ∞ (s M ): where w represents the weight assigned to [e].

3. The method according to claim 1, characterized in that The objective function y ∞ (s M ), and obtain the optimized cover signal S Mp , whose implementation includes: 3a) Set the number of loops K and the minimum value y of the objective function ∞ (s M )=+∞, current loop number k=1; 3b) Determine whether k ≤ K: If so, the sequential quadratic programming algorithm is used to optimize the cross-correlation sidelobe level of the kth cycle |r k |, proceed to step 3c); Otherwise, return to step 3a) and optimize again; 3c) Judgement k |<y ∞ (s M ) is established: If so, let y ∞ (s M )=|r k |, and set k = k + 1, and return to step 3b); Otherwise, end the loop and get the optimized objective function y ∞ (s M ) and cover signal s M , execute 3d); 3d) The optimized shield signal s M Expressed as where N m is the number of chips of the cover signal, Represents a complex set.

4. The method according to claim 1, wherein The calculation is performed to determine the cross-correlation sidelobe level PSL1 of the radar signal, and the formula is as follows: Among them, S Mp To cover the signal, s Ra is the radar signal, J k is the cyclic transfer matrix, f0 is the center frequency of the radar signal, f m is the center frequency of the cover signal; is the Doppler frequency shift matrix, diag() generates a diagonal matrix, [] H is the conjugate transpose, [] T is transposed.

5. The method according to claim 1, wherein The calculation of the cross-correlation sidelobe level PSL2 with the reconnaissance signal is as follows: Among them, S Mp To cover the signal, s R0 To detect the signal, J k is the cyclic transfer matrix, f0 is the center frequency of the radar signal, f m is the center frequency of the cover signal, is the Doppler frequency shift matrix, diag() generates a diagonal matrix, [] H is the conjugate transpose, [] T is transposed.

6. The method according to claim 1, characterized in that The calculated radar signal autocorrelation sidelobe level PSL3, the noisy radar signal autopulse compression result y Rn And perform histogram fitting, the mean of the normal distribution is μ, and the standard deviation is σ, and the formulas are as follows: s Rn =s Ra +n where s Ra is the radar signal, J k is the circulant transfer matrix, [] H is the conjugate transpose, n is a set of 10,000 Gaussian white noise signals {n i,j }, i=1,2,...10000 represents the i-th group signal, j=1,2,...N t Represents the sampling point number; radar signal with noise s Rn , recorded as the combined signal; is the convolution operation, y Rn is the pulse compression result; Rn Get the maximum side lobe Using the normal fitting function of the software, PSL 4max Perform histogram fitting, and record the mean of the normal distribution obtained after fitting as μ and the standard deviation as σ.

7. The method according to claim 1, characterized in that The sidelobe maximum value PSL according to PSL1 1max and the sidelobe maximum value PSL3 3max Define the cover success rate α, threshold T and judgment conditions, and its implementation includes: 7a) The maximum sidelobe value of the cross-correlation sidelobe level PSL1 of the radar signal and the shield signal is PSL 1max , the maximum sidelobe value of the radar signal autocorrelation sidelobe level PSL3 is PSL 3max Based on the evaluation criteria for signal sidelobe suppression and signal shielding effectiveness in radar signal processing, the effects of PSL1 and PSL3 on shielding effectiveness are comprehensively considered. The threshold is set as T, the shielding success rate α and the judgment conditions are as follows: T=1 / μ Judgment condition: 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ. 7b) Determine 1 / PSL 3max ≥1 / μ∪1 / PSL 1max <1 / μ: If so, the cover is successful, calculate the cover success rate α and evaluate the cover effect; Otherwise, the cover fails and the cover signal S is re-optimized Mp and evaluate the effectiveness of cover.

8. A shield pulse interference modulation waveform design system, characterized in that: include: Signal definition module, used to define various signal models; Signal modeling module, used to build a mathematical model of the signal; Signal optimization module, used to optimize the shield signal S Mp Optimize Sidelobe calculation module, used to calculate the cross-correlation sidelobe levels between various signals; The shield parameter module is used to define shield effect evaluation parameters; The shield evaluation module is used to evaluate the shield effect of shield signals.

9. The system according to claim 8, characterized in that The sidelobe calculation module includes: The cover signal submodule is used to calculate the optimized cover signal S Mp The cross-correlation sidelobe level PSL1 of the radar signal and the cross-correlation sidelobe level PSL2 of the reconnaissance signal respectively; Radar signal submodule, used to calculate the autocorrelation sidelobe level PSL3 of the radar signal; Combined signal submodule, used to calculate the self-pulse pressure result y of the combined signal Rn。 10. The system according to claim 8, wherein: Signal optimization module, including: The objective function construction submodule is used to construct the objective function of the cover signal; The algorithm optimization solution submodule is used to solve the objective function and obtain the optimized cover signal.

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