Research And Implementation Of Modulation Recognition Technology Of Communication Signals

Wireless spectrum monitoring receiver is mainly suitable for radio monitoring,reconnaissance and radio spectrum management,and auto modulation recognition schemes of modulated signal plays a vital role in both military and civil applications,such as radio spectrum management,interference identification,threat analysis and electronic countermeasure.Thus,the receiver with automatic modulation recognition function is more competitive in the increasingly complex electromagnetic environment.The modulation recognition algorithm is analyzed and researched in this thesis,based on the technical indicators of a monitoring receiver.Then a modulation recognition algorithm and system implementation scheme is proposed.The research background and application status of modulation recognition technology is introduced in thethesis.Then focusing onthe related technical theory of signal pre-processing and modulation recognition technologyandthe project realization is accomplished through lots of simulation and programs.In this thesis,a pattern recognition scheme based on decision-tree classifier is analyzed and designed by extracting the high-order cumulants and instantaneous eigenvalues.In the aspect of theoretical verification,the classification parameters and the identification processare analysed by the simulation in MATLAB,which verifies the feasibility of the recognition scheme.In the aspect of system implementation,the overall design scheme of the identification systemis described,and the method of digital quadrature transform is adopted to extract the baseband signal,so that it could reduces the dependence on the signal bandwidth.The modular design ideas is adoptedas follows: In the data pre-processing module,pre-processing of IF digitalized sampling sequencesand FFT operations are realized in FPGA,which provide basic data forthe follow-up identification.In the data processing module,DSP based on SYS/BIOS operating system adoptesthe multi-tasking mode to achieve the programming and debugging of the modulation recognition algorithm.In the data transmission module,the uPP interface is used to realize the data transmission between FPGA and DSP,and the TCP/IP protocol is used to realize the network communication between DSP and host computer,in order to realize the real-time online analysis of the modulation recognition.Finally,the test bench is established for testing the performance of the modulation recognition system through using the signal set {AM,FM,USB,LSB,DSB,BPSK,QPSK,OQPSK,2FSK,4FSK,16 QAM,32QAM}.The test results show that the overall recognition average accuracy of the recognition system is not less than 93% when the signal-to-noise ratio(SNR)is not less than 10 dB,which achieves the expected target.