Spatial Utilization and Suppression of Multipath Signals by Maximal-Ratio-Combining Digital Beamformer for Mobile Radios


IEICE TRANSACTIONS on Communications   Vol.E81-B       pp.806-810
Publication Date: 1998/04/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Category: Mobile Communication
digital beamforming,  adaptive array antenna,  maximal ratio combining,  multipath signal,  amplitude distribution,  

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A maximal-ratio-combining (MRC) 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, which are made possible by spatial digital signal processing. This paper describes the performance of this beamformer under the multipath signal arrivals with various path delays using numerical simulation, aimed at application to future mobile radios with high spatial utilization efficiency. The results indicate the robustness of the MRC beamformer in a multipath environment. It features multidirectional beam steering when there is small path delay in the multipath signal and gain suppression in multipath signals when their path delay is more than about one symbol. Moreover, improvement in suppression by employing low-sidelobe amplitude distribution is discussed as a means to reduce inter-symbol interference without null-beam steering.