Study On Several Issues Of Radar Active Interference Countermeasures In Multiple Domains

Radar is an important tool for information collection and plays an extremely critical strategic role in modern warfare.Radar is the primary target of enemy electronic countermeasures systems.The working performance of the radar is seriously affected by the active jamming signals emitted by the enemy.It is important and urgent to improve the anti-jamming ability of radar.The pattern of active interference is flexible and changeable.Different antiinterference strategies are adopted to deal with different interference scenarios.An interference countermeasures system covering multi-domain and multi-dimension should be constructed to ensure the performance of the system in interference environment.This paper discusses several issues of anti-jamming countermeasures from the aspects of polarization domain,waveform domain,azimuth domain and frequency domain.For noise jamming and smart noise jamming,the interference signal is suppressed in the polarization domain by filtering the signal of the dual-polarization receiving channel,which benefits from the polarization freedom provided by the dual-polarization receiving.The filter coefficients directly affect the interference suppression performance.The typical idea is to design the filter based on the characteristics of the interference signal,based on the statistical independence of the target echo and the interference signal,or based on the characteristics of the target echo.The process of estimating the characteristics of interference signals faces the difficulty of selecting interference samples.Smart noise jamming signal and target echo signal are not completely statistically independent,which also limits the performance of blind source separation algorithm.The paper proposes a transmitting waveform matching method based on target echo characteristics.The expected signal is constructed according to the timedelay relationship between the target echo and the radar transmitting signal.The constrained optimization problem is constructed and the filter coefficients are optimized to minimize the mean square error between the filter output signal and the expected signal.The interference suppression problem is transformed into the target signal recovery problem,which avoids the difficulty of interference sample selection.Simulation experiments show that the method based on waveform matching can effectively suppress noise jamming,noise convolution jamming and dense false target jamming.For Interrupted-Sampling Repeater Jamming(ISRJ),a method of ISRJ suppression based on iterative decomposition is proposed.The interference signals in the mixed signal are cancelled by parameter estimation and interference waveform reconstruction.The classic ISRJ mathematical model is a process in which the same sample signal is repeatedly forwarded.This paper generalizes the ISRJ model,and the total ISRJ can be regarded as the sum of several sub-interference signals corresponding to different sampling signals.Based on the general ISRJ model,this paper proposes a sample selection method and a time-frequency analysis method to estimate the sampling signal.For the false target formed by ISRJ,the peak amplitude after pulse compression is only contributed by some sample points.In the sample selection method,the objective function is first constructed according to the peak amplitude information.The steepest descent method is used to solve the optimization problem,and the contributing sample points are screened out.Then the sampling signal is estimated through the smoothing process.The feature values are extracted and the attributes of the object are identified.Finally,the sub-signal is canceled from the original signal.In the time-frequency analysis method,the time-frequency analysis is first performed on the received signal to determine the time and frequency sequence corresponding to the current target.Instantaneous magnitude information is extracted from the time-frequency matrix.The sampling signal is then estimated based on the correspondence with the instantaneous magnitude.Simulation experiments show that the proposed method has good parameter estimation and interference suppression performance for direct forwarding,repeated forwarding and periodic forwarding ISRJ.For forwarding deception jamming,this paper proposes a multi-radar cooperative scheme to identify false targets.The information of the target in two observation angles is fused to realize the identification of true and false targets.By adjusting the working frequency and transmitting waveform,the radar working frequency band can cover the working frequency band of the cooperative radar.Therefore,the scattering signal of the target to the cooperative radar can be received.Considering the requirements of deep notch on the spectrum stopband and low sidelobes of the autocorrelation function,a matching waveform pair design method is proposed.The radar transmits a pair of matched random phase-encoded signals(with a large bandwidth),and the cooperative radar transmits a liner frequency modulation signal(with a small bandwidth).The two signals are orthogonal in the frequency domain.The information of the two channels is separated at the receiving end by matched filtering.Real targets are shown in both channels,while false targets are only shown in the phase-encoded signal channel.For sighting jamming and sweeping jamming,it is an effective means to avoid interference by changing the carrier frequency between pulses.The random agility of the carrier frequency not only improves the anti-jamming capability,but also leads to serious high-range side-lobes.This paper discusses the problem of range sidelobe suppression from the aspects of carrier frequency design at the transmitter and mismatched filter design at the receiver,based on the prior knowledge of the observation target.The research goal is to ensure information extraction capabilities while taking into account anti-interference requirements.According to the distribution information and scattering intensity information of scatterers obtained from the previous coherent processing interval,different weights are assigned to different range bins to avoid wasting degrees of freedom.The limited degrees of freedom are allocated efficiently to improve the overall performance of the radar.The purpose of the carrier frequency design is to reduce the interaction between the scatterers and reduce the high side-lobes formed by the scatterers in the empty range bins.The objective function is to minimize the weighted integral sidelobe level.At the receiver,the mismatched filter bank is optimized to minimize the weighted integral sidelobe level.Simulation experiments show that the introduction of prior information improves the range image estimation performance in frequency agility scenarios.