SAR imaging and Doppler ambiguity removal with distributed microsatellite arrays
Abstract:This paper focuses on the removal of azimuth ambiguities of sparse apertures in distributed microsatellite radar systems. A uniform linear array is ideal for removing azimuth ambiguities. However, the effects of the elliptical orbit and the Earth's rotation make it difficult for conventional space-time processing to resolve Doppler ambiguities. In this paper, we assume that the instantaneous position vector of each satellite is known, and propose a subaperture coordinate-based method. The full aperture geometry is divided into several subaperture independent geometries, in each of which a Cartesian coordinate is constructed according to the position vector of a reference satellite. After phase error removal the baselines in each subaperture coordinate system are obtained by numerical calculation. For each subaperture's returned data, we first compensate for the phase error caused by the three-dimensional (3D) sparse arrays, and then transform the long-track sparse arrays to short along-track arrays. Using a beamforming technique, the Doppler ambiguity is suppressed for each subaperture followed by combining them into the full aperture and full bandwidth spectrum. Theoretical derivation, performance analysis and simulation results are presented.
Document Type: Research Article
Affiliations: 1: National Laboratory for Radar Signal Processing, Xidian University, Xi'an, Shaanxi, China 2: Radar and Signal Processing Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Kent Ridge, Singapore
Publication date: July 1, 2010