Towards an analytical model of I/Q imbalance in OFDM based direct conversion receivers

Architectural simplicity, the possibility of monolithic integration as well as the lack of image filter problems make homodyne receivers very popular. However, their I/Q architecture is sensitive to impairments. OFDM based systems are particularly likely to suffer from imbalances due to distortions introduced by the time-to-frequency transformation of the filtered signal in the case of a mismatch between the I and Q branches. The paper focuses on clarifying how phase and amplitude imbalances influence the baseband signal processing of an OFDM based homodyne receiver. A novel analytical impairments model is presented, discussed and compared with simulations of an IEEE 802.11a system.