LAAS Reference Antennas - Circular Polarization Mitigates Multipath Effects

A.R. Lopez

Abstract:	Early in the development of the local Area Augmentation System, LAAS, vertical linear polarization was selected for the low-elevation-angle antenna of the two-antenna reference antenna system. The initial LAAS development concentrated on ground reflected multipath. Polarization was not an issue; the level of radiation in the lower hemisphere was specified such that the ground-reflected multipath error was within acceptable limits. However, as LAAS approaches the deployment phase, other siting issues are coming to the forefront, and, polarization selection can make a significant difference. This paper reviews the issue of polarization with regard to multipath performance, and in particular, it considers the performance with respect to lateral multipath (reflections from airport objects not including ground reflection). It presents some theoretical models and past experience that demonstrate that, lateral multipath for the case of linear polarization, can cause large errors, and in some cases, can capture the receiver with an associated outlier-type error. It is concluded that if both linearly and circularly polarized antennas can satisfy the ground reflection performance requirements then circular polarization is advantageous since it provides substantial suppression of lateral multipath effects.
Published in:	Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003) June 23 - 25, 2003 Hyatt Regency Hotel Albuquerque, NM
Pages:	500 - 506
Cite this article:	Lopez, A.R., "LAAS Reference Antennas - Circular Polarization Mitigates Multipath Effects," Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003), Albuquerque, NM, June 2003, pp. 500-506.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In