IQ Imbalance Estimation Scheme with Intercarrier Interference Self-Cancellation Pilot Symbols in OFDM Direct Conversion Receivers

Direct conversion receivers in orthogonal frequency division multiplexing (OFDM) systems suffer from direct current (DC) offset, frequency offset, and IQ imbalance. We have proposed an IQ imbalance estimation scheme in the presence of DC offset and frequency offset, which uses pilot subcarriers in the frequency domain. In this scheme, the DC offset is eliminated by a differential filter. However, the accuracy of IQ imbalance estimation is deteriorated due to the intercarrier interference (ICI) components caused by frequency offset. To overcome this problem, a new IQ imbalance estimation scheme with intercarrier interference self-cancellation pilot symbols in the frequency domain has been proposed in this paper. Numerical results obtained through computer simulation show that estimation accuracy and bit error rate (BER) performance are improved.