The Research Of Communication Signal Modulation Recognition And Demodulation

The communication signals modulation recognition technology is a technology to recognize the modulate pattern by processing and analyzing the received or captured signals based on their characteristics. In this project, the algorithm of communication signal modulation recognition is discussed, a modulation recognition and demodulation receiver is designed and implemented, where auto-recognition function is realized, base on the software radio and digital demodulate technology.In this paper, the importance of the research on modulation recognition, and the status of technology in this area are discussed. Then the scheme of the project, software design and hardware implementation together with regression testing are elaborated. The Software Define Radio (SDR) structure is adopted in the design of the modulate pattern recognition and demodulation receiver. The receiver uses communication signal with intermediate frequency of 70MHz as the input, then amplifies it, pass it to an Analog to Digital converter, after that, processed it in FPGA and DSP board. The algorithm of communication signal modulate pattern recognition is done with statistic methods on signal characteristic extraction and sorting. To make the receiver available to all kinds of communication signals, SDR structure is adopted, software is designed as configurable to make the receiver flexible and tunable. Meanwhile, to achieve better signal locked threshold, dynamic range and BER performance, correlation demodulation is used in the receiver. Based on MATLAB simulation results, the algorithm is written into DSP and FPGA devices thus the modulate pattern recognition and demodulation receiver is completed. The digital down-converter, digital filters, carrier tracker and demodulator are done in FPGA board. In DSP board, the algorithm of communication signal modulate pattern recognition is implemented. In the end, a regression test is carried out with the receiver placed under different Doppler frequencies, signal input levels, SNR and modulate patterns, testing result shows that the receiver can meet the demands of engineering.