Advanced antenna technologies for satellite communication payloads
This paper addresses some of the recent developments at LMCSS in the area of multiple beam and reconfigurable beam antennas for communication satellite payloads. These advancements include (a) multiple aperture dual-band reflector antennas, (b) high efficiency horns covering 50% bandwidth, (c) a novel ?stepped-reflector antenna? (SRA) technology, and (d) reconfigurable beam antennas for HIEO and GEO satellites. It is shown that by combining the reflector improvements through the use of SRA with the feed improvements through the use of dual-band high efficiency horns (DBHEH), significant improvements in EIRP, G/T, and co-polar isolation (C/I) can be achieved. The SRA system produces ?flat-top? radiation patterns for receive beams and highly efficient Gaussian patterns for transmit beams over a geographic coverage as seen by the satellite. The DBHEH designs employ ?slope-discontinuities? to generate desired higher order modes over both transmit and receive bands. By employing a ?frequency-dependant? horn design for the DBHEH, it is shown that the step size can be significantly reduced and can be easily blended into the reflector surface for ease of fabrication. Detailed design of a K/Ka band MBA with about 68 spot beams is presented. The RF performance of this novel MBA has been evaluated and shows significant improvements in EIRP, G/T, and C/I in comparison with a conventional MBA. Comparison results of the advanced MBA with conventional MBA are presented in the paper. Design examples for both FSS and DBS satellites are discussed. A novel reconfigurable antenna suitable for HIEO and GEO satellites has been developed at LMCSS. It employs a non-focused reflector (NFR) antenna using a shaped mesh-reflector, and a small active feed array located in the focal-plane of the NFR in order to continuously reconfigure the beam(s), as the satellite goes through the HIEO orbit. The NFR approach has the advantages of reducing the number of feed array elements significantly while achieving the desired beam flexibility. Feed technology advancement for FSS and BSS satellites that includes high efficiency horns, trifurcated horns, feed networks, and trends in high power TVAC testing are briefly discussed.