A novel method of beam collimation factor estimation for eos-04 active phased array antenna

EOS-04, a C-band active array antenna based Synthetic Aperture RADAR (SAR) launched by ISRO, provides continuity of the services to its predecessor RISAT-1. It is equipped with advanced features such as full polarimetric mode and computation based onboard antenna beam forming. In this paper, we present a novel method to compute complex beam collimation factor of large-sized active phased array antenna (6m x 2m) of EOS-04 payload using far-field information of sequentially excited Transmit-Receive Integrated modules (TRiM), which consist of Transmit Receive pairs for H and V chain with controller. We utilize ISRO's Compact Antenna Test Facility (CATF) for this purpose. Estimated beam collimation factor is compared with factors generated from Near-Field measurement and close match is observed. Finally, antenna patterns are generated using far-field estimated beam collimation factors and near-field estimated beam collimation factors.