RF power and I/Q imbalance calibration in B3G/4G MIMO-OFDM systems

Radio frequency (RF) front-end nonidealities in multi-input and multi-output (MIMO) systems are more serious than in single-input and single-output systems and must be calibrated. According to the effects of RF power and in-phase/quadrature-phase (I/Q) imbalance, calibration methods for multi-input and multi-output-orthogonal frequency division multiplexing (MIMC-OFDM) systems in transmitter and interference in receiver are improved, respectively, in this article. Furthermore, a calibration scheme including I/Q imbalance errors and amplitude variations is proposed and implemented in the B3G/4G time division duplex communication system. Simulation results show that the calibration algorithms are feasible, and the bit error rate (BER) performances for MIMO-OFDM systems are improved after calibrations.