Detection and Parameter Estimation of Polyphase Code Signals Based on Fractional Fourier Transform

The polyphase code(Frank,P1,P2,P3 and P4 code) signals are a kind of typical low probability of intercept(LPI) radar signals.For the detection and parameter estimation of this kind of signals,the time-frequency distribution characteristics of the polyphase code signals were analyzed;the fractional spectrum characteristics of the polyphase code signals were also analyzed and the parameter estimation expressions of the polyphase code signals were deduced,taking Frank code signal for example.An algorithm for detection and parameters estimation of the polyphase code signals was proposed based on fractional Fourier transform(FRFT).And the algorithm first presents a method to estimate the carrier frequency of the polyphase code signals.Finally,simulations verifying the algorithm still has better signal detection and parameter estimation effect in low signal-to-noise ratios(SNR) condition.