Effects of phase discontinuities in banded data when generating holographic synthetic aperture radar images

When combining different frequency bands together, phase discontinuities at the junctions are unavoidable. This paper examines the effect of these phase discontinuities on holographic synthetic aperture radar (HSAR) images. To study the problem, an actual measured data set consisting of two frequency bands (10-18 and 18-26 GHz) is used. A system model is introduced which relates physical displacement of the target to the resulting phase shift, which varies with frequency as well as transmitter/receiver location. The phase shifts corresponding to various amounts of displacement are added to the upper frequency band, and the resulting data is used to generate difference images. These difference images are either the coherent or incoherent difference between an image generated using the original data and one generated using the phase shifted data. It is concluded that the system model is valid, and that small displacements seen in controlled laboratory environments are insignificant for the target and frequencies studied.