On the performance of standard-independent I/Q imbalance compensation in OFDM direct-conversion receivers

The growing number of different mobile communications standards calls for inexpensive and highly flexible receiver architectures supporting these standards. The direct-conversion receiver is a very attractive candidate for reaching this goal. However, unavoidable imbalances between the I- and the Q-branch of the I/Q demodulator lead to a significant performance degradation at the reception of OFDM signals. The performance of a novel algorithm for the estimation and compensation of these effects is analyzed in this paper. The novel approach does not depend on any standard-specific signal components, such as pilots or a preamble. Instead, a blind I/Q imbalance parameter estimation is performed during the ordinary receive mode. Therefore, the algorithm is applicable to a wide range of present and future OFDM communications standards.