Blind IQ mismatch compensation in OFDM direct conversion receivers

OFDM communication systems are known to be sensitive to IQ mismatch in non-ideal direct conversion receivers. Traditionally, adaptive techniques have been proposed that exploit the embedded pilot signals. However, an alternative is to exploit the signal characteristics, such as the constant modulus property of PSK modulated data. This paper proposes two frequency domain blind adaptive IQ mismatch compensation algorithms, which are based on the general Bussgang algorithm and the constant modulus algorithm (CMA). Both algorithms are shown to give a significant improvement in raw BER performance for a spectrally-flat transmission scenario and the CMA-based algorithm is shown to achieve near complete compensation for a single-frequency-network fading channel scenario.