Inter-band Coherence of Split Wide Band SAR Images; A Potentially New Information Channel

Recently-launched SAR sensors like TerraSAR-X or CosmoSkyMed are equipped with wide
bandwidth radar signal emitters. Working at large bandwidth allows reaching metric range
resolution, which combined with spotlight mode, leads to Very High Resolution (VHR) SAR
imagery.
One can also take advantage of this wide band to split it into sub-bands and generate several
lower resolution images from the same master one, each centered on a slightly different cen-
tral frequency.
These sub-images can then be used in a classical interferometric process to estimate inter-
band coherence of a given scene. This inter-band coherence reveals scatterers keeping a
stable phase behaviour along with frequency shift. In this paper, a simple model derived from
Zebker model for randomly distributed surface scatterers is proposed and examples are pre-
sented showing that scatterers can have a behaviour that deviates from the model, leading to
a new information channel.