Low complexity digital IQ imbalance correction in OFDM WLAN receivers

This work proposes a time-domain scheme for digital correction of IQ imbalance in OFDM WLAN receivers, according to IEEE 802.11a/g. Recently, the zero-IF architecture became an attractive candidate for inexpensive OFDM WLAN receivers. It avoids costly components but introduces IQ imbalance. Since OFDM, using higher order modulation, is very sensitive to non-idealities in the receiver front-end, we developed a new very low complexity scheme to estimate and correct IQ imbalance. The scheme is based on one time-domain OFDM long preamble symbol and performs excellent in AWGN conditions, even for high levels of IQ imbalance. For multipath fading conditions, acceptable performance is demonstrated. Due to its very low complexity, our new scheme offers high feasibility, and therefore, helps to greatly relax front-end requirements and to enable low-cost OFDM WLAN receivers.