Stepped frequency modulated signal ISAR imaging of ship target based on high order statistics

In Linear modulated stepped frequency (LMSF) radar ISAR imaging, conventional algorithm unable to accurately estimate the motion parameter used for coherent processing under low SNR condition. Therefore, the high resolution ISAR image cannot be generated by these methods. In this paper, a band coherent processing method based on high order statistics (HOS) is presented. Firstly, the signal of LMSF is analyzed and the equations of HOS for LMSF echoes with Gaussian noise is developed. Next, the sub-pulse phase induced by translation within one burst is obtained by acquiring the eigenvalue HOS equation. The wideband chirp signal is formed by combining the coherent processed sub-pulse. One advantage of the proposed method is its ability to produce high resolution range profile without having to estimate the motion parameter which needed in conventional method. Finally, the high resolution ISAR image is generated by compensating the phase error by Range Instantaneous Doppler (RID) techniques. The result of real data processing confirmed the effectiveness of the proposed algorithm.