The Method Investigation Of Identifying The Radar Signal Modulation

The method investigation of identifying the radar signal modulation is discussed in this dissertation.The modulation of the common radar pulse signals is studied in this dissertation, including normal signals, linear frequency signals, biphase code signals and quadrature phase code signals. Signals is identified by the method of Short-Time Fourier Transform in the time-frequency analysis, then the Time-Frequency curve abtained by the Short-Time Fourier Transform is fitted with the theory of Least Squares, and then the modulation of the radar signals can be estimated by the fitting coefficients and the fitting variances.Emulation indicates that this method can distinguish the radar pulse signals presented above, when SNR is close to 2 dB.Multi-component radar pulse signals processing is also discussed in this dissertation, mainly including the signals detection in the field of spectrum. Precise and effective detection about the signal is the precondition of the modulation identification and intra-pulse parameter demodulation in the multi-component signals processing. After analysising the multi-component signals with the method of Short-Time Fourier Transform, the spectrum in each slice of the short-time window can be observed. Signals can be detected in each slice of the window by the modified threshold acquired by the alarm probability, and the number of signals can be estimated by the secondary threshold. The algorithm can get a high rate of detection at about -3dB. Then the algorithms of signal parameters estimation, filtering and demodulation are studied as well to analysis the intra-pulse characters.The recognition of Polyphase-coded signals is a forefront subject in the idetification of radar signals. With the theory of the correlation receiver, the method presented in this paper identifies the polyphase signals(Frank code,P1 code,P2 code,P3 code and P4 code) by the algorithms of maximum-likelihood hypothesis,based on the Precise parammers estimation of the polyphase-coded signals. The method is good at low SNR.Emulation indicates that the algorithm studied in this dissertation is feasible and effective and the performance of the algorithms is good.