Frequency-selective I/Q imbalance compensation for OFDM receivers using decision-feedback adaptive filtering

I/Q imbalance in practical direct-conversion receivers is a major impairment in OFDM systems. The increasing demand for wider bandwidth and higher data throughput illuminates the need for robust and high performance frequency-selective I/Q imbalance compensation in OFDM direct-conversion receivers. Inspired by the 2005 work of Capozio, Pratima, and Vizzi, this paper presents an approach for mitigating frequency-selective I/Q imbalance using decision-feedback adaptive filtering. The presented approach may be viewed as a generalization of the cited 2005 work to frequency-selective operation. By making use of decision-feedback, a very high level of image rejection can be achieved, thereby enabling the use of higher order modulation on OFDM subcarriers. The method is online, fully adaptive, and is suitable for use in systems with digitally compensated carrier frequency offset (CFO). For the specific frequency-selective I/Q imbalance case considered, simulations show a significant improvement in the image rejection ratio (IRR) and the post compensation effective E_b/N_o, with the proposed method outperforming similar compensation methods.