Long-Time Coherent Integration for High-Speed Target Detection Based on RKT-FRFT

To improve the detection capability of radar for target, the target detection signal-to-noise ratio is usually improved by Long-Time Coherent Integration (LTCI). The LTCI needs to eliminate the problem of range migration (RM) and Doppler frequency migration (DFM) in the echo signal caused by the high-speed target during the coherent accumulation time, which allows the target parameters at the beginning of the coherent integration time to be detected. However, The range and radial velocity parameters of the high-speed target change so rapidly that there is a lag in the parameter detection results. In other words, the classical LTCI algorithms detect the initial motion parameters of the target at the final moment of integration time. Therefore, to solve the degradation of target parameter accuracy caused by the lag, a method based on reversal Keystone and Fractional Fourier transform (RKT-FRFT) is proposed. By using the reversal and rescaling operation in the slow time and fast frequency domain, a signal with the opposite characteristic of the target's motion state can be obtained, which simultaneously eliminated the range-Dopple coupling. This allows the echo energy can be accumulated in the range cell where the final integration time of the high-speed target is located. Subsequently, coherent integration is achieved by the Fractional Fourier transform (FRFT) concerning the range frequency variable. Compared to the KT-FRFT algorithm, simulations are provided that the proposed RKT-FRFT method can approach the optimal parameter detection performance with the same computational cost.