Research On Parameter Estimation Algorithm Of LPI Radar Signals Based On T-F Analysis

With the continuous development of radar technology,especially the development of low intercept probability(LPI)radar,the current challenges in electronic reconnaissance are increasing.Such as the low signal-to-noise ratio of the intercepted signal,the complex signal form and the variable radar parameters,will result in a significant reduction or even failure of the conventional parameter estimation algorithm.Therefore,the parameter estimation of LPI signal has important practical significance and research value.In this paper,we focus on the method of parameter estimation for different types of LPI radar signals using different time-frequency analysis under low SNR.The main research contents in this paper include:Firstly,the signal models and the basic theory of low probability of intercept radar are briefly introduced,mainly including binary phase shift keying(BPSK)signal,linear frequency modulation(LFM)signal,polyphase coded signal and complex modulation signal.Then we briefly introduce the theory of time-frequency analysis and the commonly used method.Here we mainly introduce the bilinear time-frequency transform,also known as Cohen class time-frequency transform.Based on the theory of ambiguity function of radar,the ambiguity functions of several typical LPI radar signals are derived,then analyze and compare their signal performance.Next,in this paper,based on time-frequency analysis,we introduce the method of parameter estimation for single-component LFM signal and a kind of complex modulation signal.The results of simulation experiment under different SNR are also presented.For the parameter estimation of multi-component LFM signal,based on the Wigner-Ville distribution(WVD)results of the signal using Hough transform,the time-frequency rearrangement(RM)algorithm is used to eliminate the cross-term interference.The RM-WVD algorithm is proposed by combining the RM algorithm with the WHT algorithm to estimate the parameters of the multi-component LFM radar signal.In the end,the principle of Lv's distribution(LVD)is introduced,and the parameter estimation experiment of LFM and LFM-BPSK signal using LVD is carried out,which proves the validity of the algorithm.Because of the derivative relationship between the polyphase coded signal and the LFM signal,based on the above work,this paper proposes an improved method of parameter estimation for polyphase coded signals under low signal-to-noise ratio(SNR).The simulation results show that the improved method for polyphase coded signals can achieve accurate parameter estimation under low SNR,and with good robustness.