Joint adaptive transmitter/receiver IQ imbalance correction for OFDM systems

Abstract

Direct conversion architectures are increasingly popular as they enable lower implementation costs. However, the receiver is very sensitive to IQ imbalances in particular for complex modulation techniques such as 64-QAM and above typically used for high data rate transmission. Conventionally, this IQ imbalance is only corrected at the receiver while the imbalance at the remote transmitter is assumed to be pre-corrected. However, aging, manufacturability, and temperature variations can be difficult to calibrate and can result in performance degradation (e.g., range reduction, etc.). We propose an adaptive scheme in the receiver to correct the IQ imbalances at the remote transmitter as well as the receiver. The proposed scheme, as it jointly corrects the IQ imbalances, is therefore more robust than the earlier results.