Time domain synthetic bandwidth methods: A 0.1 m resolution SAR technique

Current high resolution airborne SAR systems aim to produce SAR imagery at resolution less than 0.1 m. This demand poses a lot of technological and methodological problems, which have to be solved. The most important problem is bandwidth management. It can be realized by means of the synthetic bandwidth technique, an advantage of which is the reduction of the instantaneous bandwidth and sampling rate requirements of the radar system. This paper demonstrates two time domain synthetic bandwidth methods, which are respectively applied to basal receive and deramp receive mode. Based on analysis of the processing steps of original methods, the modified methods are proposed, and some issues arising in practical implementation of the technique are discussed. More particularly, the parameters choice and the overlap division processing steps of the second method in wide swaths are pointed out specifically. Moreover, according to the spectral representation of the received signal, an approach of conversion from single center frequency SAR raw data to stepped center frequencies SAR raw data is brought forward, and some results of verification of these methods are shown.