THREE-DIMENSIONAL SAR WITH FIXED TRANSMITTER AND ITS SCATTERING EXPLANATION

During the experimental data processing, we find that corner reflectors cannot be focused properly using 3-D SAR with a moving transmitter due to the phase reversal phenomenon based on the phase history analysis, i.e. the phases at different observation angles might shift rad, and the echoes cancel, rather than accumulate, to each other. To overcome this defect, 3-D SAR with fixed transmitter is designed. Since the geometry of the transmitter and targets remains unchanged during the observation session, the coherence of echoes is well preserved. The mechanism of 3-D SAR with fixed transmitter can accurately be explained using the Stratton-Chu equation. For perfect conductor, the 3-D image is related to the electric current density. For general dielectric medium, the 3-D image is related to the electric current density, magnetic current density and directional vector of scatterer. Experimental results show that one can focus corner reflectors and cavity-shaped objects by fixing the transmitter, which might fail for the traditional 3-D SAR because of the phase reversal phenomenon.