Calibration techniques for active RCS-targets

A Dual Reflector Compact Test Range is a versatile environment for measuring antenna radiation patterns as well as the Radar Cross Section (RCS) of radar targets. It is a common practice to achieve adequate accuracy for the antenna measurements by calibrating the test zone with a well-known standard, e.g. a calibrated standard gain horn. This method may not be sufficient for highly accurate measurement of test objects with antennas at offset positions. This paper shows a calibration technique used in the DLR Compact-Test-Range for an active C-band RCS-target with its TX- and RX-antenna at offset positions. The in-orbit analysis of today´s remote sensing satellite´s antenna diagrams with active RCS-targets is advantageous, because the processing, retransmitting and recording of the satellite signals on the ground test site can be remotely controlled. To fulfill the amplitude accuracy requirement of these active RCS-targets off 8.1dB, the measurements in the Compact-Test-Range are improved by correcting for the plane wave zone characteristics. Using pairs of calibration targets in a cross calibration setup enhances the overall accuracy. It is shown that this technique can be further extended for the evaluation of the plane wave zone.