A reconfigurable 28/37GHz hybrid-beamforming MIMO receiver with inter-band carrier aggregation and RF-domain LMS weight adaptation

This paper presents a hybrid beamforming mm-wave MIMO receiver with two key innovations. First, it can be configured into three modes: two single-band multistream modes at 28 or 37 GHz that can support single-or multi-user MIMO, and a concurrent 28 and 37GHz dual-band single-stream phased-array inter-band carrier-aggregation mode. In all modes, the receiver features full connectivity from each antenna element input to each output stream, thereby maximizing usage of the available aperture. Second, the digitally programmable RF beamforming weights can be controlled by an external serial interface, or by an on-chip “one-port” mixed-signal adaptation loop that implements a technique that we call double-sampling time-multiplexed LMS (DS-TM-LMS). Unlike conventional LMS-type adaptation algorithms that require access to the individual array inputs and the combined output, and are therefore not easily amenable to a hybrid beamformer, DS-TM-LMS updates the RF-domain weights by accessing only the combined downconverted array outputs. Such adaptation is valuable for adaptive main-lobe, side-lobe or null steering, but more importantly, it can assist/augment codebook-based beam acquisition/tracking algorithms, which may fail in the presence of multipath, on- or off-channel interferers.