Hybrid Analogue Digital Outphasing Beamforming Architecture with Amplitude and Phase Control

Abstract

A partially connected hybrid analogue-digital beamformer architecture with adjustable amplitude and phase weights in both the digital and the analogue part is presented. Amplitude control in the analogue beamformer is enabled by a lossless passive outphasing network.
The architecture is designed to be implementation-friendly as the only required RF components are low-resolution phase shifters, power dividers, and hybrid couplers.
If phase shifters of arbitrary resolution are assumed, any beamforming weights can be generated, whereas finite resolution phase shifters naturally lead to quantisation in amplitude and phase.
In that case, in order to find the optimum phase shifter states for approximating a given beamforming vector, a full search over all possible states is necessary.
To avoid the associated computational costs, a suboptimal but faster and less memory consuming algorithm is presented.
Furthermore, an antenna arrangement for sub-connected hybrid beamforming utilising low-redundancy sub-arrays is proposed. For sub-array based processing, the performance in the presence of a sparse channel can be improved compared against conventional antenna arrangements.