ISAR echoes coherent processing and imaging

The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a rotating target for the next processing. But in this method, scatterers' migration through resolution cells (MTRC) caused by rotational motion is neglected. However in practice, MTRC exists with the improvement of resolution or for big target. For MTRC compensation, a keystone transformation in SAR is used in this paper. Before keystone transformation, it is demanded that the raw data is coherent, while in fact, the ISAR raw data is usually not. So a coherent processing of raw data is proposed. In this paper, the coherent processing of raw data is firstly done and the next step is to correct MTRC. Finally a parameter estimation method of multi-component amplitude modulation and linear frequency modulation (AM-LFM) signal is proposed to estimate the scatterers' instantaneous amplitudes and frequencies, and the range-Instantaneous Doppler (RID) ISAR image is obtained. The effective of this algorithm is testified by the processing of simulation data.