Multipath Suppression Capability and Indicators for Airborne Dual Frequency GNSS Antennas

Abstract

Current satellite navigation systems are providing more and more dual frequency capabilities, enabling an improved navigation accuracy and reduction of residual errors (e.g. from ionosphere)[1,2]. Recently, the aviation community has started an effort to achieve new standardized minimum operational performance specifications (MOPS) for GNSS equipment, in order to allow for use of dual frequency multi constellation (DFMC) systems in the future, with clear benefits in terms of obtainable navigation performance. In such conditions, residual errors due to the GNSS antenna become more and more relevant and actually need to be properly identified and bounded, both in the antenna specifications and, for instance, in the models for aircraft multipath. Previous work from the authors [3] has shown the methodology developed in order to accurately simulate the installed performance (both in terms of antenna pattern distortion and multipath) of commercial antennas mounted on commercial aircraft. The antennas are measured in an anechoic chamber and then the data are imported into electromagnetic simulation software. Combining these measurements with a proper CAD model of an airplane, they are then used to simulate the real-life installation on the airplane. In this work, an analysis of the multipath performance obtainable by different antennas mounted on different aircraft (single aisle and wide body) will be shown: such results will provide a good indication for the performance to be expected in real-life scenarios and will also be used to further validate (and ensure the general applicability of) the new proposed model for multipath, obtained from flight data and shown in a concurrent paper at the conference. Moreover, the multipath suppression indicator (MPSI) will be introduced which is able to quantify the multipath suppression capability of the antennas: its applicability in the avionic context will be validated against the data obtained by the installed performance analysis and a proposal for its use in future antenna MOPS will be given.