L-band integrated feed array design for mobile communication satellites

The contract for the North American Mobile Communication Satellite System (MSAT) was awarded to Spar Aerospace Limited and Hughes Aircraft Company in December 1990. Spar is responsible for the satellite payload design, integration and testing. The space segment of a mobile communication satellite system such as MSAT must provide high radiated power densities on the ground to allow mobiles with small, low-gain antennas to communicate via satellite. With the emerging high-power mobile communication satellite systems, the risk of interference caused by Passive Intermodulation (PIM) is now recognized as a very important spacecraft design performance parameter. Separate transmit and receive reflector antennas are used on the MSAT spacecraft to reduce the risk of PIM. In addition, PIM avoidance is a major design driver for the transmit antenna reflector and primary feed array. Significant design effort and breadboard activities at Spar have resulted in the development of a primary feed array suitable for mobile satellite applications. This paper presents the integrated feed design approach which has been selected to meet the challenging requirements. The paper describes the feed element, which consists of an output band-pass filter integrated with a cup dipole radiator. The measured test results of the developed hardware are also presented.