Interferometric absolute phase determination with TerraSAR-X wideband SAR data

Wideband SAR systems such as TerraSAR-X bring the range resolution down to the order of the carrier wavelength. This opens the possibility to determine not only the fractional phase of SAR interferograms, but also the absolute phase value including the unknown number of integer phase cycles. This possibility enormously helps all interferometric applications such as DEM generation or land surface motion determination. Here we review the basic theory of such processing techniques and show a number of recent results from an ESA study aimed at developing an operational system. Furthermore we show how such techniques can be optimized by the use of customized 'split-bandwidth' chirp signals in place of the standard chirps used in contemporary SAR systems.