Study On Suppression Algorithms Of Radar Active Jamming

In recent years, with the progress of the ECM and ECCM technology, the working environment of the modern radar system is in a much worse electromagnetic environment. In addition, the rapid development of the electromagnetic jamming technology has realized the multi domain coverage of a radar signal. Therefore, it is of great theoretical value and practical significance to study the parameters extraction of radar echo signal and its jamming suppression algorithm in the harsh electromagnetic environment. In this thesis, we research on the suppression algorithms of suppressing jamming and deception jamming. The main work and research results are as follows:Firstly, the mathematical model of three types of active suppressing jamming and active deception jamming are introduced respectively, and different types of active jamming characteristics are presented through simulation results. The coverage of time domain and frequency domain of radar echo signal by suppressing jamming is analyzed by combining the time domain waveform and spectrum characteristics of suppressing jamming, and the deception of false target jamming to radar echo signal is described using the matched filtering method.Secondly, aiming at the problem that the low accuracy of frequency estimation will lead to serious performance degradation of the noise amplitude modulation jamming suppression, a new method based on high accuracy frequency estimation is proposed. The amplitude of the spectral line in the Candon and Rife method is weighted and the influence of the modulation noise on the frequency estimation accuracy is also eliminated by linear superposition. Then based on Ip DFT, the spectral region covered by DFT and DTFT is interpolated, so as to refine the discrete spectrum region and estimate the best frequency offset in different segmentation regions. The estimated frequency is used to demodulate the jamming, and to suppress the jamming by the frequency domain cancellation in the end. The simulation results show that the proposed method has good performance of frequency estimation and can effectively suppress the noise amplitude modulation jamming in strong interference background.Finally, to address the problem that the coupling between the jamming and the target echo is so high that the performance of conventional anti-jamming measures will degrade significantly in both the time domain and the frequency domain when the LFM radar in dense false deception-target jamming environment, a dense false-target jamming suppression method based on the improved variable step size adaptive filtering is proposed. In this method, the stretch dechirping technique is utilized to eliminate the quadratic term of the signal, and the target echo and the jamming could be separated in the frequency domain. Therefore, signal components with different frequencies could be obtained. Then, a new variable step size adaptive filtering method using the Versiera-like function is applied to regulate the step size and filter the stretch processed echo signal. The dense false-target jamming is eliminated and the target echo is recovered by the application of inverse stretch processing in the end. Simulation results show that the method which is proposed in this paper has a good robustness in the environment of low SJR, and can effectively suppress the dense false-target jamming.