Research On Modulation Classification Of Complexly Modulated Signals

In order to adapt to the increasingly complex electromagnetic environment, modulation mode has a transformation from single to complex. In view of the advantages of strong anti-jamming capability and low probability of intercept, etc. that complexly modulated signals have, their research and identifications have become a hotspot in modern signal reconnaissance processing.Based on the background above, the classifications of OFDM signal and FSK/PSK hybrid modulated signal belonging to complexly modulated signals are studied in this paper. Feature extraction methods in modulation classification are firstly analyzed in detail and simulated; subsequently the thesis summarizes their advantages and disadvantages. On this basis, an algorithm of comprehensive classification features is put forward. It realizes the classifications between OFDM signal and single carrier modulated signals and that of MASK(M=2,4,8), MPSK(M=2,4,8), MFSK(M=2,4,8) and MQAM(M=16,64) of 11 kinds of single carrier modulated signals successfully by adopting different classifiers. In addition, the performance of each classifier is analyzed. Simulation results show that the correct classification rate (CCR) of each signal is above 95% at the signal-to-noise ratio (SNR) of more than 10 dB, and the selection of classifier or classification standard needs comprehensive considerations. Finally, the recognition of FSK/PSK hybrid modulated signal is studied, mainly with MFSK signal having two kinds of forms: continuous phase FSK modulation (CPFSK) and discontinuous phase FSK modulation (DPFSK).When the classifications of FSK/ PSK and DPFSK are discussed, instantaneous frequency is firstly estimated based on high-order cumulant and wavelet ridge line, then a new feature parameter is extracted. Simulation results show that the proposed algorithm realizes the recognition of FSK/PSK hybrid modulated signal, making it have a high CCR in the low SNR.