Research On The Technology Of Blind Demodulation Of The MPSK Communication Signal

Phase Shift Keying (Phase-Shift-Keying PSK) signal is a kind of common digital communication modulation signal. Because of its high power and high utility of spectrum, it has found wide application in communication, mobile communications and satellite communication. Because of this, it also is one of the types of modulation which are very concerned in communication countermeasure system. In order to obtain more detailed signal parameters, communication reconnaissance systems often need to demodulate various communication signals. Different from demodulation of signals in communication system, communication reconnaissance system is lack of prior knowledge communication signals, thus its demodulation is almost blind demodulation. Therefore, it is of great significance to study blind demodulation for PSK signal.This paper introduces the modulation and demodulation principles of PSK. According to the demand of blind demodulation of MPSK(M-Phase-Shift-Keying), blind demodulation includes parameters estimation and demodulation. The part of parameters estimation firstly discusses methods of obtaining PSK signal’s complex envelope using Hilbert transform, analyzes PSK signal’s high-order cyclic cumulants, and estimates frequency and initial phase of carrier by using PSK signal’s four-order cyclic cumulants. Secondly the four-order cyclic cumulants can also be utilized to construct the invariants of classifying features. Then, based on the analysis of wavelet transform, a algorithm is provided, which can estimate the symbol rate of PSK signal using the Haar Wavelet Transform. On the basis of signal parameters estimations,this paper completes blind demodulations of BPSK and QPSK signals by using the quadrature demodulation algorithm.In this paper, the algorithms above are simulated by Matlab to justify the effectiveness of the algorithms.