Research On Digital Signal Modulation Recognition Technology

In order to determine the modulation mode of the received signal in the condition of signal concentration and noise interference,modulation recognition technology is usually used.Modulation recognition technology has been widely used in civil and military wireless communications,such as signal monitoring,information interception,interference identification and electronic warfare.And Modulation recognition is the basis of cognitive radio,spectrum sensing and other fields,so the research of this technology has never stopped and people pay more and more attention.In this paper,the modulation recognition technology of digital communication signals are studied and explored based on the previous work,the main achievements and innovations are summarized as follows:(1)Aiming at the problems of modulation recognition of four kinds of digital signals including MASK,MFSK,MPSK and MQAM,according to the difference of wavelet transform envelope between before and after normalization modulated signals,recognition algorithm based on the difference of wavelet coefficients of variation and wavelet feature similarity is proposed.First of all,wavelet coefficient difference and wavelet similarity under different wavelet scales are used as the characteristic parameters of MASK,MFSK,MPSK and MQAM signals.Then,in the class recognition of modulation signals,higher order cumulants and standard deviation of non normalized wavelet transform envelope are respectively used as characteristic parameters for the recognition of modulated signals.The method has the advantages of low complexity and strong fault tolerance,and has a good recognition efficiency in low SNR environment.(2)In order to deal with the problem of signal modulation recognition in the time-frequency domain aliasing signal environment,a recognition method combining high order cumulants and cyclic moments is studied.First of all,the high order cumulants of the aliasing signals are analyzed by this method.Then,the cyclic moment feature is introduced to increase the recognition range of higher order cumulants.Finally,combining tworecognition features,the support vector machine(SVM)based on the structural risk minimization criterion are used to identify the ten kinds of multiple signals modulation modes which are obtained by the combination of the four kinds of signals.This method has strong robustness and it can recognize more signal types with less feature parameters.