Analysis of IQ imbalance on initial frequency offset estimation in direct down-conversion receivers

The effect of IQ imbalance on the initial frequency offset estimation algorithm in an orthogonal frequency division multiplexing (OFDM) direct conversion receiver is studied. The impact of the phase and amplitude IQ imbalances and channel response on the frequency offset estimation is formulated for a flat channel case. Analysis of the IQ imbalance on the frequency offset estimation is provided and the results are presented in this paper. The results show that the frequency offset estimation algorithm generates an error in the estimated offset frequency with IQ imbalance and the error can be reduced by an appropriate choice of the correlation window length.