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 all standards. The direct conversion receiver is a very attractive candidate to reach this goal. However, unavoidable imbalances between the Iand the Qbranch of the I/Q demodulator lead to a significant performance degradation at the reception of OFDM signals. In this paper a novel compensation algorithm is presented to overcome this problem. 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.