Adaptive Estimation/Compensation Scheme of IQ Imbalance with Frequency Offset in Communication Receivers

IQ signal processing is widely utilized in today’s communication system. However, it usually faces a common problem of front-end distortion such as IQ imbalance and frequency offset. Effective algorithms exist for estimating and compensating for IQ imbalance as well as frequency offset, when the two problems are treated separately. With both effects present, such algorithms do not lead to useful estimates of the related parameters. In this paper, we propose a robust technique to estimate and compensate for the IQ imbalance in the presence of carry frequency offset (CFO) by using a known preamble of repeated training sequence. In addition, to solve the problem of performance degradation when CFO is small we developed an adaptive scheme with small residual degradations. The performance of such a scheme has been validated by computer simulations on IEEE 802.11a signals. And it is shown that the proposed method is more robust and renders better performance than existing algorithm.