Digital Signals Modulation Classification Research And Application

Modulation classification (MC) plays a key role in various civilian and military applications, especially in military areas such as Radio Reconnaissance and Electronic Warfare。This paper discusses the blind estimation algorithms of carrier frequency and symbol rate. New definitions called discrete-degree and discrete-degree spectrum have been firstly proposed and used in the detection of the discrete line of the square spectrum. The new method overcomes the effect of the lower roll-factor effectively. Based on the discrete spectrum lines successfully detected, A self-adoption symbol rate estimation structure have been used to estimate the symbol rate of different signals. A modified frequency offset estimation algorithm is proposed. The news method offers a three levels digitally heterodyning and decimate filtering structure, and the frequency offset is reduced step by step. The modified algorithm has a higher resolution and lower SNR threshold.Based on the carrier frequency and the symbol rate successfully estimated, the paper studies the modulation classification of digital signals in microwave and satellite communications. The modulated signal set is composed of BPSK, QPSK, OQPSK, π/4QPSK,8PSK,16QAM,32QAM,64QAM,128QAM and256QAM. A mixed MC structure is proposed. The computer simulation shows that the new structure can recognize the ten kinds of modulated signals effectively.At last, the paper discusses the application of the algorithm mentioned above.