Research On Identification And Parameter Estimation Of Complex Modulated Signals

In this paper, radar signal recognition and parameter estimation in the field of electronicsurveillance were studied. First the signal models of common radar signals were built, and then theprinciple of common radar signal recognition was introduced. Finally the simulations of therecognition algorithm were made by MATLAB. The signal recognition method mainly used is basedon phase unwrapping. Through orthogonal transformation of the received signal, starting-ending timeestimation and phase unwrapping, the instantaneous phase and frequency of the received signal can begot. The radar signal recognition can be achieved according to the time-phase and time-frequencycharacteristics.The study of complex modulation signals was focused on. Complex modulation signals mainlyinclude LFM signal, SFM signal, polyphase coded signals (Frank code, P1code, P2code, P3codeand P4code), SLFM signal, LFM-BPSK signal and FSK-BPSK composite modulation signal. Theadvantages of the complex modulation signals were discussed and the recognition was realizedthrough the time-phase and time-frequency characteristic. Then the parameters of the recognizedsignals can be estimated respectively.Lastly a detailed analysis of the FSK-BPSK signal was carried out. As the frequency curve trippoints were caused by different factors, we re-spliced the time-frequency curve after striking out thesignal transition points. Transition points caused by phase were removed，that caused by FSK stillexisted. So the signals can be identified accordingly and the signal parameters estimation can becarried out.The final simulation results show that the proposed method can identify the signal modulationwith high accuracy in a low SNR environment. Parameter estimation is accurate. And all aboveproves that the proposed method could be applied to engineering practice.