High Precision Antenna Characterisation for Broadband Synthetic Aperture Radar Processing

The airborne F-SAR sensor[1], developed and operated by the DLR-HR institute, acquires very high resolution, fully polarimetric synthetic aperture radar (SAR) data in multiple frequency bands in addition to providing a number of interferometric imaging modes. The high resolution/high bandwidth regime of operation introduces significant challenges in terms of data calibration as well as image formation, or focusing. This paper reviews the difficulties encountered in both areas and highlights the importance of compensating for the characteristics of the antenna in overcoming them. A prerequisite to doing so are highly accurate measurements of these characteristics, which are themselves difficult due to the fact that they must accurately portray interactions with the surroundings when mounted on the aircraft. The results presented concern the antenna characterisation itself and illustrate how the quality of real polarimetric and interferometric SAR data can be significantly improved when these characteristics are properly taken into account.