16-QAM impedance loading board design supporting single RF beamspace MIMO system

This paper presents a design of a 16-QAM impedance loading RF transmission system using six-port correlator and switching chips, as well as its performance evaluation. The proposed system only consists of passive components and switching chips, and thus it obviates the need for using number of RF components (e.g. mixer, filter, and DAC) which must be used in the conventional MIMO RF system. It significantly improves overall power efficiency and decreases system complexity. The impedance loading board is verified via 3 m Tx-Rx air transmission experiment. It achieves EVM of 10.5% when transmitting 1 Mbps 16-QAM signal with 20 dBm power at 1.93 GHz carrier frequency.