Active antenna with electronic scanning in azimuth and elevation, particularly for microwave imaging by satellite

摘要

Offset active antenna with two co-focal reflectors (5,7) and radiofrequency lens (12) at their common focus, equipped with electronic scanning in azimuth and/or in elevation, especially for microwave imaging by synthetic-aperture radar from a satellite circulating in low orbit. The antenna is constructed according to the "Gregory" geometry, with an auxiliary reflector (7) illuminated by an active array (6) of elementary sources fed by fixed-gain amplifiers (9) with a phase imparted by variable phase-shifters (8). The beam (10) emitted by the elementary sources and reflected (14) by the auxiliary reflector (7) is focussed on the electronic lens (12), which reemits a divergent beam (17) towards the primary reflector (5), which will be reflected into a parallel beam (11). The electronic scanning of the final beam (11) is achieved by acting on the phases imparted by the primary phase-shifters (8), and possibly by phase-shifters (18) for fine adjustment in elevation. IMAGE