Multipath Rejection Through Spatial Processing

The development of low cost, small size antenna arrays and digital antenna electronics has resulted in small, affordable GPS phased arrays and digital receivers that are suitable for commercial applications. NAVSYS Highgain Advanced GPS Receiver (HAGR) product includes the capability to spatially process signals from up to 16antenna elements. Previous papers have presented the HAGR’s capability to perform beamforming, in both static and mobile environments, providing over 10 dB of additional signal gain on each satellite tracked. This capability results in highly accurate code and carrier tracking providing superior performance for high accuracy applications, such as kinematic GPS. In this paper, a further enhancement to the HAGR digital signal processing is described. A spatial signal processing algorithm has been developed that allows multipath signals to be detected and an adaptive antenna array pattern is then used to minimize their received signal power while still applying gain in the direction of the direct GPS signals. Test data is included showing the benefit of this method in reducing the multipath errors on both the pseudo-range and carrier-phase observations.