Modulation Recognition And Parameter Estimation Of Communication Signals

The automatic modulation recognition technology of communication signals can identify the modulated format of a blind signal based on the proper processed results from these noisy signal samples. It has attracted great interest recently in non-cooperation communication, especially the electronic confrontation.In the thesis, the principle of the modulation recognition is firstly introduced, which includes the analysis of most commonly used digital modulation signals, instantaneous parameter extraction, mathematical theory of higher moments and higher-order cumulants. Secondly, the recognition algorithms based on instantaneous statistical feature, spectral analysis and higher-order cumulant are deeply studied and analyzed, respectively. After these simulations of each parameter in these algorithms, the advantages and disadvantages of the aforementioned algorithms are demonstrated. Further, a synthesized recognition algorithm which can achieve the recognition of2ASK,4ASK,BPSK,QPSK,2FSK,4FSK,16QAM signals by analyzing the parameters of maximum value of the spectrum power density of the normalized centred instantaneous amplitude(γm3x),maximum value of the spectrum power density(Speak),three arguments based on high-order cumulants(arg2,arg1,arg4) is proposed. The corresponding flow diagram and simulated results based on the Matlab software for each format modulated signal are given in the thesis, and thus it shows that the overall recognition rate of more than90%and97%can be separately realized under the SNR of detected signal is higher than6and8dB.Finally, algorithm of parameter estimation including carrier frequency estimation and symbol rate estimation is introduced. The intermediate frequency estimation algorithm in frequency estimation is improved, which reduce the relative error to be0.01, more than tenfold compared to the original algorithm. For symbol rate estimation, power spectral characteristic of delay product is used to estimate the symbol rate of QPSK signal. Simulation results show that symbol rate of QPSK can be precisely estimated for the SNR being higher than3dB.