Research On Parameter Estimation Of The Complex Phase Coded Signal

With the modulation of radar signal becoming more complex, the electronic reconnaissance technology faces more and more severe challenges, and there is practical significance and application value to study the parameter estimation of LPI radar signals. In this thesis, based on time-frequency analysis, parameter estimation of several complex phase coded signals is estimated. The main work and research results are as follows:Firstly, introduce several mathematical models of LPI radar signal, including the binary phase shift keying signal, polyphase coded signal, linear frequency modulation and binary phase shift keying signal, polyphase coded signal, linear frequency modulation and polyphase coded signal. The parameters of the above LPI signal, the characteristics of the signal and the waveform characteristics are studied. According to the basic theory of Time-frequency analysis technique, such as short-time Fourier transform, Cohen time-frequency analysis, ambiguity function, LVD transform, etc. The characteristics and properties of each time frequency analysis are described, which lays a theoretical foundation for the subsequent parameter estimation.Aiming at the problem of linear frequency modulation and binary phase shift keying signal parameters estimation, a corrected LVD method to estimate the carrier frequency and time-frequency rate of the squared signal is proposed. Firstly, use LVD algorithm to rough estimate the signal carrier frequency and time-frequency rate, get the dechirp signal, and then use LVD algorithm to estimate the dechirp signal, estimating the carrier frequency and time-frequency rate, repeat this step until the carrier frequency and time-frequency rate is zero or less than the set threshold. Finally ZAM transform is used to estimate code-width of LFM-BPSK signal. The simulation results show that the method can be modified, at low SNR to achieve high accuracy of carrier frequency, and symbol width estimation of chirp rate. The simulation results show that at low SNR the method can achieve high accuracy of carrier frequency, time-frequency rate, and code-width estimation of LFM-BPSK.Aiming the problem of low accuracy of parameter estimation for the polyphase coded signal under the low SNR, a method of LVD-FRFT parameter estimation is proposed. Firstly, the method use LVD to estimate the carrier frequency and time-frequency rate of the polyphase coded signal, then get the optimal rotation angle of FRFT, so that the code-width of polyphase coded signal can be estimated. This method improves the efficiency of the search, and improve the estimation precision of the parameters of the polyphase coded signal in low SNR environment. For the problem of the linear frequency modulation and polyphase coded signal, we use the ZAM transform to estimate the phase point mutation, and estimate time-frequency rate of the linear frequency by using the coherent solution line modulation of the two adjacent points. Finally, the time-frequency rate of the polyphase coded signal can be estimated.