A Consolidated GNSS Multipath Analysis Considering Modern GNSS Signals, Antenna, Installation, and Boundary Conditions

Abstract

This study investigates the multipath error for modernized GNSS signals considering the: GNSS code and carrier signals; GNSS antenna characteristics; GNSS receiver architecture; and the installation configuration, including the reflecting boundary for a ground-based GNSS installation. The GNSS signals explicitly considered in this analysis are GPS L1 C/A, L5, L1Cp, BOC (10,5); Galileo ALTBOC, and the QZSS L6 signals. With the GNSS code and carrier multipath delay predictions at a fixed signal-to-multipath ratio using a coherent correlator architecture, the installed code and carrier multipath delay predictions are initially produced. Then multipath error predictions consider the two orthogonal GNSS antenna components, as modified by the complex reflection coefficient at the ground reflecting boundary modeled as wet soil. The multipath environment is modeled as a single specular ray, with due consideration to the polarization reversal at the Brewster angle from the reflecting boundary. The GNSS antenna will receive a composite signal that consists of the combination of the desired right-hand circularly polarized GNSS signal received above the horizon, and the undesired multipath signal that is predominantly left-hand polarized except when below the Brewster angle. Using these GNSS signal, receiver, antenna, receiver, installation, and reflection characteristics the final installed code and carrier multipath errors are predicted. Lastly, for a given GNSS installation that has a multipath limit that needs to be met, the antenna desired-to-undesired performance envelope limits are presented. These data will prove useful to GNSS site, antenna and receiver designers to illustrate the contributing factors in multipath error and what to expect if they sited their GNSS receiver and antenna systems in a particular configuration.