Design of a Center-feed Waveguide Feeder for Wideband Rectangular Parallel-plate Slot-array Antenna on-board Space-borne X-band SAR System

In this paper, we aim to design a waveguide feeder for a parallel plate slot array antenna for a high resolution Synthetic Aperture Radar system on-board a 100 kg micro satellite called Micro-XSAR, scheduled to be launched by Japan Aerospace Exploration Agency by 2020. In order to increase the antenna beam-width and thereby mitigate the frequency dependent beam-shift, we employ center feeding using a two-way power divider named the iota-junction instead of the conventional end-feed design. Further, we re-model the iota-junction by adding a pair of inductive walls to get double resonance instead of existing single resonance to significantly suppress reflection and hence substantially enhance the bandwidth. The HFSS simulation results show that by employing double resonance, we can increase the bandwidth upto 300 MHz thereby increasing our SAR image resolution from 3 meters to 1 meter which validates our innovative idea.