Determination of absolute interferometric phase using the beam-amplitude ratio technique

Determination of the absolute phase difference (i.e., not module 2π) is a key problem in interferometric synthetic aperture radar (IFSAR) for topographic mapping. One way of solving this problem requires use of a technique different from the basic interferometry to resolve a “coarse” angle measurement that lies within the IFSAR ambiguity angle. The method investigated in this paper involves taking advantage of the difference in the amplitude ratio versus elevation angle that occurs when the elevation beams of the two IFSAR antennas are pointed in slightly different directions. The performance of the technique is a function of the angular separation of the two beams, the elevation beamwidth, and the symmetry of the two beam-amplitude patterns. The performance required of the technique is set by the ambiguity angle of the interferometer. This paper presents an analysis of the beam-amplitude ratio technique and shows experimental results