Satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

A compact dual-band mobile satellite-tracking antenna system for mounting on a movable body for communicating with a satellite in earth orbit, said antenna system comprising:

• a reflector dish having a non-symmetrical aperture with major and minor axes, said major axis being aligned in a generally horizontal direction and said minor axis being aligned in a generally vertical direction;
• a feed-horn having a back end and an open front end facing said reflector dish at a focal point thereof and comprising vertical side walls opening out from said back end to said front end at a first horn angle and horizontal top and bottom walls opening out from said back end to said front end at a second horn angle, said first horn angle being less than said second horn angle;
• means for transmitting to said feed-horn signals of a first frequency band for transmission via said reflector dish to said satellite and receiving from said feed-horn signals of a second frequency band reflected by said reflector dish from said satellite;
• and
• antenna attitude control means for maintaining an antenna azimuth direction relative to said satellite, wherein said reflector has a fixed elevational angle corresponding to an elevation of said satellite;
• and wherein, said major axis is aligned in a generally horizontal direction and said first horn angle is chosen whereby to maximize azimuthal directionally of said reflector dish, and said minor axis is aligned in a generally vertical direction and said second horn angle is chosen whereby to minimize elevational directionally of said reflector dish to an extent corresponding to expected pitch excursions of said movable body.

A compact dual-band mobile satellite-tracking antenna system for mounting on a movable body for communicating with a satellite in earth orbit, said antenna system comprising:

• a reflector dish having a non-symmetrical aperture with major and minor axes, said major axis being aligned in a generally horizontal direction whereby to maximize azimuthal directionality of said reflector dish and said minor axis being aligned in a generally vertical direction whereby to minimize elevational directionality of said reflector dish to an extent corresponding to expected pitch excursions of said movable body;
• a feed-horn having a back end and an open front end facing said reflector dish at a focal point thereof and comprising vertical side walls opening out from said back end to said front end at a first horn angle and horizontal top and bottom walls opening out from said back end to said front end at a second horn angle, wherein said first horn angle is less than said second horn angle, and wherein said reflector dish and said feed-horn are mounted on a generally horizontal platform rotatable in azimuth;
• means for rotating said rotatable platform through an azimuth angle in response to sensed yaw motions of said movable body so as to compensate for said yaw motions to within a pointing error angle;
• means for sinusoidally dithering said rotatable platform through a small azimuth dither angle greater than said pointing error angle while sensing a signal from said satellite received at said reflector dish;
• means for extracting amplitude variations in said signal sensed from said satellite corresponding to sinusoidal dithering of the rotatable platform by the means for sinusoidally dithering and for deducing therefrom said pointing error angle, and for transmitting a correction signal corresponding thereto to said means for rotating.