Han, Bing; Ding, Chibiao; Liang, Xingdong; Wang, Yanping; Hong, Wen (National Key Laboratory of Microwave Imaging Technology, Institute of Electronics, Chinese Academy of Sciences, P. R. China)
Han, Bing (University of Graduate, Chinese Academy of Sciences, P. R. China)
A coupling between subpulses and the ’fast’ time is introduced when stepped-frequency pulse burst is applied to SAR to obtain ultra high range resolution, i.e. there is range migration among pulses in one burst. Traditional methods which simply combine synthetic HRR processing method and conventional SAR imaging algorithm can not remove the coupling which will bring phase discontinuities in adjacent subpulses and inevitably degrade SAR imaging, for the range migration within pulse bursts does not keep constant at all integration angles. This paper first concisely analyzes the causes, behaviors and main characteristics of the coupling mentioned above, and then studies a new method for steppedfrequency SAR imaging which is called the Subimage Coherent Accumulation Method (SCA). Compared with traditional ones, this method can accurately correct range migration of all subpulses by adjusting the sequence of signal processing and adding some simple operations. Stepped-frequency SAR image formed by SCA obviously has better imaging quality than that by traditional methods. This paper will give the detailed deduction and show some of the simulation results.