Time-domain frequency-dependent I/Q imbalance compensation based on golay sequence

Abstract

A time-domain golay complementary sequences based frequency-dependent I/Q imbalance compensation scheme for receiver is presented. By utilizing property of golay sequences, the signal and its conjugate interference in preamble are separated by correlation and used to estimate the equivalent channel of I branch and Q branch. After that, a filter which contains the difference of those equivalent channels is estimated by Least Square Error (LSE) method and adopted to compensate the imbalance. The compensator structure is designed to fit the scheme so that the phase imbalance is not needed to estimate separately during the compensation. The provided scheme could be effectively applied in standards like 802.15.3c or 802.11ad where golay sequence is adopted as preamble of a frame so that there is no cost in frame structure. All the estimation and compensation are operated in time-domain thus no FFT operation is needed. Also, no further information about the channel is required, which ensures the imbalance distortion could be eliminated right after synchronization in the receiver before channel estimation and equalization. Thus, there is no strict on the algorithms of channel estimation and equalization. The performance of the scheme is evaluated by computer simulation and compared with existed algorithms. The results show that it has effectively eliminated the influence of the imbalance at a low complexity.