A compact C-Band CP-SAR microsatellite antenna for Earth Observation

Abstract

This work describes the development of a compact Circularly Polarized SAR C-band antenna system and the design considerations suitable to use on small spacecrafts. To reduce size and weight of the small spaceborne SAR, we utilize a lightweight deployable parabolic mesh reflector and operate at low Earth orbital altitudes. The antenna is a wrap-rib center-fed parabolic reflector with dedicated receiving and transmitting feeds. Antenna requirements are: center frequency of 5.3 GHz with bandwidth of 400 MHz and circular polarization with axial ratio better than 3 dB. Simulation of the parabolic reflector and effects of different structural elements to the main radiation pattern is analyzed, which include ribs, struts, feed blockage and mesh surface. A research model of the parabolic reflector was constructed. Surface verification was realized using two different approaches, one using a laser distance meter along ribs and the other using 3D scanning of the reflector surface, with respective surface accuracy of 1.92 mm and 3.86 mm RMS. Near-field antenna measurements of the deployable reflector mesh antenna was realized for final antenna validation, presenting good agreement with the simulation results. Future work comprises of prototyping and testing of the full polarimetric feed assembly.