I/Q Imbalances in QAM Communication Systems with Multi-Antenna Receivers and IF Architecture

The Inphase/Quadrature phase (I/Q) imbalance is an inevitable problem in wireless communication systems due to imperfections in the transceiver hardware. In this paper, we investigate the effect of I/Q imbalance in Quadrature Amplitude Modulation (QAM) communication systems adopting multiantenna receivers and the IF (Intermediate Frequency) architecture. Two application scenarios are studied: adaptive beamforming and Blind Source Separation (BSS)-based multiuser detection. For both applications, after analyzing the interference introduced by the transceiver I/Q imbalance, we illustrate that, like systems adopting the zero-IF architecture, straightforward digital signal processing algorithms can be applied in systems with the IF architecture as well to correct the effect of I/Q imbalance. The differences between systems adopting the zero-IF and IF architectures are clarified. Computer simulation results are presented to confirm the conclusions of theoretic analysis.