Study Of Parameter Estimation And Anti-jamming Performance Of LPI Radar Signals

In recent years, with the development of the radar electronic countermeasure technology, The working and living environment of modern radar systems is becoming more complex, and the electromagnetic interference technology aimed at radar gets rapid development. Therefore, the research work of parameter estimation and its anti-jamming performance of radar signal under complicated electromagnetic environment is imminent, which has important theoretical significance and practical value. In this thesis, the parameter estimation and its anti-jamming performance in complex electromagnetic environment based on several typical LPI radar signal is deeply researched, the main work and research results are as follows:Firstly, three kinds of active blanket jamming and the basic theory for LPI radar signal processing are introduced, and then a signal anti-jamming performance evaluation model based on ambiguity function and matched filter is proposed. The ambiguity function and the derived active area and cutting area of radar signal can analyze the signal anti-jamming performance qualitatively and quantitatively from the perspective of the signal’s characteristic separating the signal processing methods, intercept demodulation, interference detection and other factors, and it has important theoretical value. At the same time, radar signals are match filtered under three kinds of jamming to verify its anti-jamming performance by analyzing the improvement of the SJR.Secondly, to address the problem that conventional parameter estimation performance degrades significantly under low SNR, a parameter estimation method based on the fractional autocorrelation and the S-RAT is proposed. The fractional autocorrelation is first introduced in this method to implement the estimation of the frequency modulation slope. Then the definition of the S-RAT is proposed and the Radon transform is carried out along the signal’s ambiguity function ridge. Therefore, the peak interval of the RAT could be extracted effectively by utilizing the second order difference which can eliminate the bridge basal produced by the Gaussian white noise. Simulation results show that the proposed method offers superior parameter estimation performance for P4 polyphase coded signals in the blanket noise frequency modulation jammingenvironment.Finally, the anti-jamming performance evaluation of LPI radar signals under complex electromagnetic environment is researched on the basis of the evaluation model proposed above, and several typical signals are simulated and analyzed, including the STLFM signal, the phase coded signal and the chaotic signal. The STLFM signal with overlapping inclined blade type ambiguity function has good resistance to radio frequency and modulation interference, overcoming the distance Doppler coupling of the traditional LFM signal. Three phase coded signal has pin type ambiguity function, and due to repeated cycles characteristics of the signal, the ambiguity function plane are arranged rules peak. Chaotic signal with ideal pin type ambiguity function and excellent anti-jamming performance accords with the requirement of modern radar system.