The Application of Single Reflector Multi-Feed Antennas to Direct T.V. Satellites

The antenna technique associating a single offset-fed reflector cut out from a revolution paraboloid to a multi-element feed source is being widely used for telecommunication satellites. This paper shows over the example of the French coverage area that the antenna technique is also an excellent solution for direct T.V. Broadcast satellites because of these decisive features : - large flexibility of design, enabling an optimization of the power distribution across the aperture of the feed source. - very low cross-polarization levels, owing to the array geometry, the good performance of each element and the cancellation of the polarizer errors. - competitive gain performance provided by the use of a high efficiency feed element. - straightforward implementation of R.F. sensing to eliminate the beam pointing error caused by the residual variations of the satellite attitude. - rugged waveguide technology providing broadbandwidth performance. The single reflector multifeed antenna technique can be accurately modelled by a computer program, and it is exempt of technical uncertainty. Measurements performed on an engineering model have confirmed the exactitude of the computer prediction.