Impacts of I/Q imbalance on QPSK-OFDM-QAM detection

The impacts of the I/Q imbalance in the quadrature down-converter on the performance of a QPSK-OFDM-QAM system are studied. Either amplitude or phase imbalance introduces inter-channel interference (ICI). In addition to the ICI, there is a cross-talk between in-phase and quadrature channels in each and every sub-carrier when both amplitude and phase imbalances are present. The BER (bit error ratio) performance of QPSK sub-carriers are also calculated to illustrate the impacts of the I/Q imbalance. It is observed that with the amplitude imbalance less than 1 dB and phase imbalance less than 5 degrees, the degradation of BER performance is less than 0.5 dB for a BER>10^-6