IQ Imbalance Estimation Scheme with Weighting Factor in OFDM Direct Conversion Receivers

Abstract

Direct conversion is a scheme of directly converting an RF signal into a baseband signal without passing through an intermediate frequency. Since a circuit for converting to an intermediate frequency is unnecessary, the circuit configuration can be simplified. However, this receiver has the problem of IQ imbalance, which is mainly due to the mismatch of the elements between I phase and the Q phase. The phase mismatch occurs when the phase difference is not exactly 90 degrees and the gain mismatch occurs due to the difference in the gain of the I phase and the Q phase of LO signal. In this paper, IQ imbalance compensation scheme is proposed. The proposed scheme compensates the IQ imbalance using pilot signals and the weighting factor with simple computational complexity. In this research, the proposed scheme is evaluated through numerical simulations. Simulation results show that the bit error rate performance is improved even in the presence of IQ imbalance.