Research And Implementation Of Modulation Identification Of Communication Signals Under Low SNR Conditions

Modulation recognition of communication signals is always being an important topic in the field of wireless communications, and a key technology of electronic reconnaissance confrontation. In modern electronic warfare, in order to secure communication, the communication signal power tends to be low, and in the process of wireless communication, a variety of noise may be superimposed to the signal, which leads to the SNR of the signal is very low. How to correctly judge the communication signal modulation in low SNR conditions, and give the corresponding modulation parameters is a key step before signal demodulated, and achieve the purpose of signal interception ultimately.Firstly, this paper introduces the background and development trend of domestic and international research projects. According to the current phase-modulated signal and the signal amplitude and phase modulated signal widely applying in the field of electronic surveillance confrontation, proposing the signal model of this study, and conducting digital down conversion to the signal according to the actual engineering process on software radio in the MATLAB platform,verifying the feasibility of the signal model. Then resarching the BPSK, QPSK, 16 QAM these three signals Fu style spectrum and higher-order cumulants features, in MATLAB simulating and extracting the BPSK, QPSK, 16 QAM feature quantity of these three signals in MATLAB platform, and achieving automatic identification for these three signals.A method that execute autocorrelation to the signal and then analyze its high-order spectrum is put forward,for the the problem that the recognition rate of the higher-order spectrum analysis to the signal is low,and advancing the rate of recognition to the signal in low SNR.Secondly, in the case of completing MATLAB theoretical analysis identified, according to the scounting process of electronic reconnaissance confrontation, giving the realization program that based on Interface management module and signal processing module to the modulation recognition of the communication signal, completed the hardware design, selection of core component and designment of system module. Then, completed the FPGA, DSP, PowerPC software programming, and debugging the main module, showing the results.Finally, the design of the system to complete the system joint experiment of signal reconnaissance receiving for the modulation recogniton system that designed,obtaining the recognition rate of signals of the experiment,and prelimiary analysis the experiment results.