Performance analysis of two-sided IQ imbalance effects in OFDM systems

The direct conversion is an attractive architecture, as compared to the traditional heterodyne approach, for both transmitter and receiver design. In spite of its great advantages in hardware implementation, direct conversion results in several negative effects, such as IQ imbalance, flicker noise, DC offset, even-order distortion, etc. In this paper, we study the IQ imbalance problem of the OFDM transceiver with direct conversion architecture. The IQ imbalance effects at both transmitter and receiver are considered in the multipath fading channel. To assess the influence of IQ imbalance, a comprehensive system performance analysis is derived for ideal channel information. Besides, the impacts of IQ imbalance on the practical channel estimation scheme, i. e. maximum likelihood (ML), are studied. It is shown from the numerical results that image reflection ratio (IRR) should be kept above 30 dB to alleviate the influence of IQ imbalance.