LAAS/GBAS Ground Reference Antenna With Enhanced Mitigation of Ground Multipath

Alfred R. Lopez

Abstract:	The concept for the ARL-1900 LAAS/GBAS ground reference antenna was first described at the ION 2000 National Technical Meeting. This antenna has the following features: • One-port circular-polarization L1-L2-L5 coverage of the upper hemisphere • Sharp antenna pattern cutoff on the horizon for mitigation of ground multipath at low elevation angles • 30 dB sidelobes in the lower hemisphere for mitigation of ground multipath at higher elevation angles • Very high quality carrier delay (antenna phase center) and code (group) delay characteristics • Circular polarization at low elevation angles for mitigation of lateral multipath This antenna has been under development since 1999, and is now entering the initial phase of field deployment. The prototype ARL-1900 antenna was built under contract to the FAA. After successful testing by the FAA, in December of 2005, 17 additional antennas were built and tested. Ten additional antennas are currently being built. This paper reviews the ground multipath issue and describes a means for enhanced mitigation of the ground multipath problem. The variability of the ground reflectivity is quantified and its impact on the possible variation of the ground multipath error is described. Siting recommendations are made which enhance the multipath performance
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	389 - 393
Cite this article:	Lopez, Alfred R., "LAAS/GBAS Ground Reference Antenna With Enhanced Mitigation of Ground Multipath," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 389-393.
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