Robust Beamforming for GNSS Synthetic Antenna Arrays

The impetus for this paper and the underlying research is to investigate and develop robust beamforming algorithms with synthetic antenna arrays for GNSS signals. The concepts of synthetic array based beamforming and Angle-Of-Arrival (AOA) estimation for Global Navigation Systems (GNSS) signals are described in this paper. The core idea is the utilization of GNSS antenna motion to synthesize a virtual antenna array for GNSS spatial processing (beamforming and AOA estimation). Since only a single antenna is used, the amount of data for processing is the same as other conventional temporal or frequency processing techniques. However, the visualization of received signals in the spatial domain provides a great potential for signal separation, such as interference and multipath mitigation. Several classical beamforming techniques previously developed for a physical real array are applied to a synthetic array based system. Their performance is compared theoretically in terms of the antenna beamforming beam-pattern. Angle of arrival estimation for GNSS signals is successfully demonstrated with both simulated datasets from an advanced hardware simulator and field measurements. The potential synthetic array based spatial processing for the case of unknown antenna trajectory is introduced at the end of the paper.