LAAS Multipath Limiting Antenna (MLA) Performance Testing and Analysis

D. Bryce Thornberg, Mark Dickinson and Dan Aloi

Abstract:	The amplitude and Desired-to-Undesired (D/U) antenna patterns of the LAAS Multipath Limiting antenna (MLA) have been tested and analyzed in detail [1 & 2]. In [3], an electromagnetic model, based on the method of moments, of the 14-element MLA showed excellent correlation for relative phase center variation and Desired-to-Undesired gain ratio. Several studies have suggested, however, that secondary antenna pattern effects contribute to the obtainable accuracy of the LAAS system. Some of the areas tested, analyzed and discussed in this paper are the MLA’s phase and group delay pattern response. Due to the antenna’s large vertical height, the antenna exhibits a significant phase variation as a function of vertical angle. This phase variation also contributes to a non-constant group delay which is also a function of the antenna’s vertical pattern. If uncompensated for, the phase variation and the group delay can add secondary errors to the LAAS system [4]. Detailed testing of the phase and group delay patterns for both the dBs 200 (14 element MLA) and the dBs 200A (16 element MLA) was accomplished. Methods to maximize the accuracy of these measurements were employed to obtain measurements with minimal phase noise. The test set-up and methods are discussed and detailed measurement results are presented. Updated phase patterns are presented which allow more accurate phase center correction of the MLA. Precise location of the mechanical phase center for both the dBs 200 and dBs 200A are presented. High fidelity test data outlining the detailed azimuthally variant amplitude vertical patterns of the MLA were also measured. These detailed patterns are also presented. The MLA’s tested were installed in the field at the William J. Hughes Technical center and field data was compared against the detailed antenna test range data to identify any corresponding error contributing parameters. Results of this field testing are presented. The phase, amplitude and group delay response of the dBs 200 and dBs 200A under heavy icing conditions were measured and are reported. Simulated ice buildup using a composite material with similar dielectric properties to ice was utilized for the simulated ice measurements.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	140 - 152
Cite this article:	Thornberg, D. Bryce, Dickinson, Mark, Aloi, Dan, "LAAS Multipath Limiting Antenna (MLA) Performance Testing and Analysis," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 140-152.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In