Ang Li 0003 Christos Masouros Mathini Sellathurai Analog-digital beamforming for tunable-load MIMO by mutual coupling exploitation. 1-5 2017 SPAWC https://doi.org/10.1109/SPAWC.2017.8227792 conf/spawc/2017 db/conf/spawc/spawc2017.html#LiMS17