Inventors:
Monty W. Bai - Scottsdale AZ
Keith A. Kingston - Mesa AZ
Hugh R. Malone - Phoenix AZ
John G. Doggett - Chandler AZ
Ronald P. Vidano - Scottsdale AZ
Earl R. Yingling - Chandler AZ
Assignee:
Motorola, Inc. - Schaumburg IL
International Classification:
H01Q 300
Abstract:
The present invention provides two approaches for eliminating a keyhole problem associated with an azimuth-elevation gimbal antenna which is a problem that occurs when the antennae is tracking a satellite vehicle that is substantially directly overhead, i. e. , the satellite vehicle is near the zenith position. At such a point, the azimuth motor of the gimbal antenna must turn very rapidly when the satellite passes through such near zenith position. A first approach involves tilting up one of the elevation axis joints when the antenna points at or near its zenith position such that the pointing angle may be altered by a predetermined angle, for example around 0. 5. degree. to 1. degree. , from the zenith position. A second approach involves tilting the secondary reflector of the cassegrain antenna such that the pointing direction of the antenna may be altered by a predetermined angle.