A 94 GHz Monopulse Duplexing Horn Antenna for a 3-D Tracking Radar

Abstract

This article presents the first demonstration of a full-waveguide feed at W-band, enabling transmit–receive duplexing and 2-D tracking of targets. The proposed device is a compact unit designed to be used as feed of a 94 GHz space-borne radar. Its duplexing concept relies on a septum orthomode transducer polarizer for transmitting and receiving sum signals with opposite circular polarizations. Additionally, the first higher order mode of circular waveguide (TM01) is allowed to propagate inside the device to extract a difference signal for tracking. By comparing received sum and difference signals in amplitude and phase, both angular directions of a target position can be derived. A prototype of the duplexer was fabricated and tested: measurements at 94 GHz show return loss and isolation above 23 dB at all ports, with reasonable performance from 92 to 96 GHz. The measured monopulse characteristic enables 2-D tracking of targets deviated by less than 8.5° from boresight.