Joint Estimation and Compensation of TX and RX IQ Imbalance for Direct-Conversion Transceiver

For direct-conversion transceiver, IQ imbalance is significant at both transmitter (TX) and receiver (RX), which brings in image interference and degrades the transmission quality. In order to handle this problem, the maximum-likelihood algorithm is employed to jointly estimate TX and RX IQ imbalance, and the corresponding Cramer–Rao lower bounds (CRLBs) are calculated. Furthermore, a compensation mechanism is proposed to combat IQ imbalance, which is derived from the criterion of maximum signal-to-interference-plus-noise ratio (MSINR). In addition, comprehensive simulations indicate that the mean square errors of the proposed estimation coincide with the CRLBs. Also, the proposed MSINR compensation achieves competitive performance, in terms of both SINR and bit error rate.