MIMO Receiver with Reduced Number of RF Chains Based on 4D Array and Software Defined Radio

Multiple-input multiple-output (MIMO) technique is expected to be extensively used in future wireless systems to increase capacity of wireless channels. Nevertheless, the capacity gain comes with a cost. In particular, multiple analog radio frequency (RF) chains are required at both the transmitter and the receiver, thereby leading to a higher implementation cost, more power consumption, and lower energy efficiency. This paper presents a receiver with only one RF chain for $2 \times 2$ MIMO transmission system. Proposed design is based on a time modulated antenna array (TMAA) with beam-steering functionality and a wideband software defined radio (SDR). Spatial streams were created by demultiplexing spectral components (sidebands) generated by periodical ON/OFF switching. Number of RF chains was reduced from 2 to 1 while maintaining sufficiently low correlation of spatial streams, which is required to perform MIMO transmission. Feasibility of proposed technique is evaluated by means of experimental verification.