Power-based Capon beamforming: Avoiding the cancellation effects of GNSS multipath

This paper addresses the problem of GNSS multipath mitigation using antenna arrays. A new data-dependent beamforming technique is proposed that is based on the well-known Capon beamformer. This technique aims to avoid the typical cancellation phenomenon between signal and correlated multipaths, by exploiting the known power of the direct signal at the receiver. To this effect, a measure of the correlation between the signal and multipaths is obtained in matrix form, and it is then subtracted from the spatial correlation matrix of the received signal. This results in a new spatial correlation matrix that is used for the final Power-Based Capon beamformer. The behaviour of this technique is justified mathematically, and it is supported by several numerical results. These results show that the obtained multipath attenuations are generally superior to those obtained by other existing techniques, and also that the noise response is very satisfactory. The impact of the proposed technique on the time-delay and carrier-phase calculation at the GNSS receiver is also considered. While the obtained carrier-phase observables are reasonably accurate, the final distortion on the time-delay is exceptionally low for any multipath delay.