Performance comparison of reflector and AESA-based digital beamforming for small satellite spaceborne SAR

Master Thesis


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Spaceborne Synthetic Aperture Radar (SAR) sensors play an ever increasingly important role in Earth observation in the fields of science, geomatics, defence, commercial products and services. The user community requirements for large, high temporal and spatial resolution swaths has driven the need for low-cost, high-performance systems. The increasing availability of commercial launch vehicles shall bolster the manufacturing and industrialisation of a smaller class sensor. This work deals with the performance comparison between a small satellite class planar array and reflector antenna system. Here the focus lies on digital beamforming techniques for the operation in wide-swath, high-resolution stripmap mode. For this the sensor sensitivity and ambiguity suppression performance in range and azimuth are derived. The Jupyter notebook environment with code in the Python language served as a convenient mechanism for modelling and verifying different performance aspects. These performance metrics are simulated and verified against existing systems. The limitations the spherical Earth geometry has on the transmitter timing and the imaged scene are derived. This together with the SAR platform orbital characteristics lead to the establishment of antenna design constraints. A planar array and reflector system are modelled with common design specifications and compared to a sea ice monitoring scenario. The use of digital beamforming techniques together with a high gain reflector antenna surface provided evidence that a reflector antenna would serve as a feasible alternative to planar arrays for spaceborne SAR missions.