A fast method for intra-pulse parameters estimation of polyphase-coded radar signals based on FRFT

Due to the complex intra-pulse modulation of polyphase code signals, most research on intra-pulse parameter estimation algorithms has focused on utilizing techniques such as the Wigner-Hough transform (WHT), Radon-ambiguity transform (RAT), and other methods. In this paper, we studied the fractional Fourier transform (FRFT) normalized domain of polyphase-coded signals and derived a mathematical model to prove the impulse characteristic of the polyphase-coded signals under optimal order. This is the theoretical basis for the fourth-order origin moment as the objective function, and an algorithm based on FRFT is proposed to estimate the intra-pulse parameters of polyphase-coded signals. The simulation results show that the relative root-mean-square error (RRMSE) of this algorithm is less than 0.03 when the SNR is above - 5 dB. The proposed algorithm is compared with the traditional algorithm by the time error product (TEP), which has obvious advantages in efficiency and is suitable for engineering practice. Furthermore, considering the difficulty in obtaining prior information on parameters in non-cooperative environments, which leads to the inapplicability of evaluation standards such as mean square error (MSE), we propose an evaluation standard for parameter estimation based on a posteriori models. Through simulations, this standard is proven to be as persuasive as MSE.