T/R Module Performance Monitoring of the TerraSAR-X Active Phased Array Antenna

Abstract

The German remote sensing satellite TerraSAR-X, launched in 2007, hosts a flexible X-Band synthetic aperture radar (SAR) operating in Stripmap, Spotlight, ScanSAR, and additional experimental modes. For these various antenna beams, its active phased array antenna electronically steers and shapes the patterns in azimuth and elevation direction. The array consists of 384 radiating sub-arrays for horizontal and vertical polarisation each. Each individual array element is controlled by a transmit/receive (T/R) module to adjust phase and gain in a very short time. This paper demonstrates the excellent accuracy of this novel PN Gating technique down to accuracies of better than 0.1dB. During on-ground characterisation of the TerraSAR-X instrument this technique has established as a crucial diagnostic tool for functional checks. After launch, this innovative method is applied for in-flight performance monitoring of the TerraSAR-X antenna front-end. The technique described above is also applicable for characterisation and calibration of other advanced sensor systems coping with active phased arrays.