Doppler ambiguity resolving in distributed micosatellites radar Imaging

The anntenna area of distributed micosateliites radar system is usually smaller than the minimum Synthetic aperture radar (SAR) antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to develop processing approaches that exploit the added degrees of freedom of a spatially diverse formation to resolve inherent ambiguities of this sparse aperture distributed microsatellites radar system. This paper proposed a Doppler ambiguity resolving method which makes the Doppler ambiguities null in Doppler domain using spatial filter of multiple phase centres, this processing can be regard as a Space-time processing (STAP). This method first filters out each unambiguous frequency point from ambiguous Doppler channels of a few different phase centers by using spatial filter, then combines all unambiguous real frequency point to a whole unambiguous Doppler band, after that, finishes imaging processing. The theoretical derivation for along-track linear array and three dimensional array, performance analysis and simulation of the method are also given in the paper.