Assessment of Processing Methods for Stepped Frequency Airborne SAR

Recently, the E-SAR system of DLR has been upgraded to stepped-frequency mode in X-band to improve the range resolution of SAR images. Initially the resolution was limited by the maximum chirp bandwidth/sampling frequency of 100MHz. The stepped frequency operation mode of the ESAR system uses two different frequency steps and leads to an improvement of up to 80% in the range resolution. The hardware-upgrade was limited to RF-front end modifications, thus keeping data acquisition hardware and system control software more or less unchanged. However, for the case of the E-SAR system, the processing of stepped frequency data is new. The demand was for additional software modules for processing stepped-frequency waveforms. The outcome of this thesis is a prototype processor to be used by DLR to process stepped-frequency data acquired by its SAR systems