Blind I/Q Imbalance Compensation in Multipath Environments

Mismatches of the amplitudes and phases of the I and Q signal branches in quadrature receivers result in insufficient rejection of the image frequency band. Particular sensitiveness of modern re-configurable transceivers reinforces the need for efficient mitigation of I/Q imbalance. This paper introduces two algorithms for I/Q imbalance compensation: blind source separation and a novel low order statistics method. A signal-to-noise-and-distortion ratio based measure to evaluate the performance of the algorithms is used. It is observed that the results of I/Q imbalance compensation are highly coupled with the dependencies between the mismatches in the transmitter and the receiver. Therefore a known frequency offset in the transmitter is introduced. Due to this operation, the mismatches may be treated as two independent impairment sources, and the compensation is performed in two stages. Results of a theoretical study are verified by extensive Monte Carlo simulations for multipath fading environments.