Joint compensation of IQ imbalance and phase noise

Today a lot of effort is spent on developing inexpensive OFDM receivers. Especially, zero-IF receivers are very appealing, because they avoid costly IF filters. However, zero-IF front-ends introduce more front-end distortion such as IQ imbalance and phase noise. Unfortunately, OFDM is very sensitive to these receiver non-idealities. Therefore, we developed a new estimation/compensation scheme to jointly combat the IQ imbalance and phase noise at baseband, taking channel estimation into account. In this paper, we describe the algorithms and present the performance results. Our compensation scheme eliminates IQ imbalance based on one OFDM symbol and performs well in the presence of phase noise, the overall system performance is within 0.6 dB of the optimal case. As such, our estimation/compensation scheme greatly relaxes the mismatch specifications and enables low-cost zero-IF receivers.