Algorithm and hardware architecture of high accuracy IQ imbalance estimation and compensation for OFDM system

IQ imbalance is one of the most serious problems in direct-conversion receiver because it introduces signal constellation error and channel estimation error which lead to worse bit error rate. In this paper, we present algorithm and hardware architecture of IQ imbalance estimation and compensation in an OFDM system based on IEEE 802.16-2009 Fixed WiMAX standard. In order to accurately estimate the IQ imbalance, we use estimation in both time domain and frequency domain. The estimation is adaptively changed between time and frequency domain based on the estimated CFO. We also propose an architecture of IQ imbalance estimation and compensation which employs CORDIC and resource sharing method. Performance of the architecture was verified by confirming that MSE of the bit-precision model is not significantly deteriorated compared with the floating-point model in all tested channel models and CFO variations.