Spatial utilization and suppression of multipath signals by maximal-ratio-combining digital beamformer for mobile radios

A maximal-ratio-combining digital beamformer has been studied to attain open-loop and automatic self-beam steering towards both desired and multipath signals at the same time and diversity combining of the signals, made possible by spatial digital signal processing. This paper describes the performance of this beamformer under multipath signal arrivals with various path delays by means of numerical simulation. The results show the features of multidirectional beam steering when the path delay of the multipath signal is small and the gain suppression of the multipath signals when their path delay is more than about one symbol. Moreover, improvement of the suppression by employing a low-side-lobe amplitude distribution is discussed as a way to reduce intersymbol interference without null beamforming.