Detection and Parameter Estimation of Polyphase Codes Radar Signal Based on Fractional Autocorrelation

Polyphase codes radar signals (Frank, P1, P2, P3and P4 codes) derived from linear frequency modulated (LFM) waveforms have been widely used in low probability of intercept (LPI) radar. To solve the problem of higher computational complexity in detection and parameter estimation of the polyphase codes radar signals, a fractional autocorrelation based algorithm is proposed. The paper proved that the fractional autocorrelation at an arbitrary angle exactly corresponds to the radial slice of the signal ambiguity function (AF) at that particular angle, based on which a detection method of polyphase codes radar signal is proposed. After that the parameter of the polyphase codes radar signal was estimated via the combination of fractional autocorrelation and fractional Fourier transform (FrFT). The proposed method, which does not compute the time-frequency plane and can be achieved by the FFT, observably reduces the computational complexity of polyphase codes radar signal detection and parameter estimation. The computer simulations verify the effectiveness of the proposed method.