A 12m Cassegrain Antenna with "Off-Set" Feed System for Two Frequency Ranges and Monopulse Tracking with Bearing Error Correction

A 12m Cassegrain antenna for the space monitoring service is described, which is designed for an overall bandwidth of 1.5 to 13 GHz. With the present receive equipment it can be operated alternatively in three different frequency bands (1.52-1.79 GHz, 2.1-2.3 GHz, 10.95-11.8 GHz). A novel offset feeding principle makes it possible to switch between these bands within < 1 min, the retrofitting of additional bands is planned in the future. The accuracy of the monopulse tracking (TE21-modes) is reduced by the influence of certain interference modes which are internally generated by the feed system. A special passive network is finally discussed which compensates the resulting pointing errors.