THE "SLOPE" EFFECT OF COHERENT TRANSPONDER IN INSAR DEM

Abstract

Although a Coherent Transponder (CT) is widely utilized in the field of Synthetic Aperture Radar (SAR), its Digital Elevation Model (DEM) has not yet been well studied for Interferometry SAR (InSAR). Based on the fact that the interferometry phase is a constant for CT with single transmit antenna, this paper mainly focuses on InSAR DEM induced by CT. The decorrelation effect in the intersection region of CT and natural terrain is researched in detail to support the analysis of CT's phase-unwrapping. The most important property, which makes DEM of CT unique, is found to be the "slope" effect. The incline angle of "main slope" of DEM is verified to be determined only by the depression angle of InSAR baseline, whereas the incline angles of the "subordinate slopes" are affected by all the geometric parameters of InSAR baseline. Finally, all the incline angles are independent of CT's waveform modulations, since the modulations have no contribution to the interferometry phase.