Dual-polarised T/R antenna system suitable for FMCW altimeter radar applications

The authors propose a dual-polarised T/R antenna system that utilises a 3 dB 90deg hybrid coupler and a dual-polarised antenna. From the practical point of view the T/R isolation performance of this system can be made better than that of systems using circulators. There is no power loss both in transmit and receive modes compared to 6 dB total loss in a conventional system using a hybrid coupler and a single polarised antenna. To validate the system performance, a sample structure is realised for a C band application. The presented system analysis and measurements are for an above-ground application. The measurements show good agreement with the theoretical expectations