Antenna Range Measurements for Airborne Remote Sensing Antennas

Abstract

The DLR Compact Test Range (CTR) is a dual reflector compact range in an electromagnetically shielded chamber for antenna and Radar Cross Section (RCS) measurements under far-field conditions [1]. The quiet zone dimensions allow an evaluation of a volume under test, containing the antenna under test (AUT) in position on the original support structure and surface. Precise in-situ parameters offer extra information about the installed AUT characteristics. These properties are particularly substantial for the radiometric and the polarimetric correction of the propagating signals in imaging microwave sensors, such as Synthetic Aperture Radar (SAR) instruments. F-SAR [2] is a high-resolution multi-frequency fully polarimetric airborne SAR with interferometric capabilities that is developed and operated by the DLR Microwaves and Radar Institute. Spherical swept frequency antenna measurements with continuous moving axis and forward/reverse scanning on offset position AUTs impose specific demands on the analysis. Higher order modes that are present due to test setup and physical constraints are considered in the post-processing. Still, stray signals from the antenna carrying aircraft structure in the proximity contribute to the antenna pattern and remain unfiltered. The particular requirements and status of the applied measurement and processing techniques are described.