Mitigation of Static Carrier Phase Multipath Effects Using Multiple Closely-Spaced Antennas

Abstract

The effect of carrier phase multipath in static mode is investigated and a system is developed to reduce the effect using multiple closely-spaced antennas. The correlated nature of multipath, along with the known geometry among the antennas, are used with the measured relative carrier phase differences to aid in the extraction of the direct carrier phase from the multipath-corrupted carrier phase measurement. The mathematical model of the multipath effects on carrier phase measurements and the Kalman filter implemented to estimate these errors are described. The model is first tested on simulated data in which the antenna geometry and reflector parameters were varied. It was then tested on field data collected on a roof whereby the model adaptively estimates the parameters of the composite multipath signal. Initial results demonstrate substantial mitigation of carrier phase multipath signals from multiple sources using this technique under static conditions. The RMS value of the average multipath error on a single differenced carrier phase measurement data is typically reduced by over 70% percent. This technique estimates the parameters of the composite multipath signal and removes the error due to all multipath signals. It is particularly useful for reference stations which transmit carrier phase data for kinematic positioning applications.