Study of the I/Q Imbalance Problem in Adaptive Beamforming Receivers

Adaptive beam formers employ an array of antennas to achieve maximum reception in a particular direction. The exploitation of spatial separation among user signals originating from different transmitters offers great potential for increased spectrum usage efficiency and system capacity. In this paper, we address the issue of Inphase/Quadrature phase (I/Q) imbalance in adaptive beam forming receivers, which is caused by nonidealities in the receivers' analog front-end. While most of the research on I/Q imbalance focuses on single-antenna receivers, the I/Q imbalance problem for multi-antenna systems received more attention in recent years due to the popularity of Multiple-Input-Multiple-Output (MIMO) scheme. The presented study in this paper concludes that the I/Q imbalance problem in adaptive beam forming receivers may be mitigated via simply increasing the number of antennas, and the I/Q imbalance-induced interference can be considered a special type of co-channel interference. Our conclusion is confirmed by computer simulation results.