Estimation scheme of the receiver IQ imbalance under carrier frequency offset in communication system

IQ signal processing is widely utilised in today´s communication systems. However, it usually faces a common problem of front-end distortion such as IQ imbalance and carrier frequency offset (CFO). Effective algorithms exist for estimating and compensating for IQ imbalance as well as CFO, when the two problems are treated separately. With both effects present, most of those algorithms suffer from degraded quality parameter estimates. In this study, the authors proposed a scheme to estimate and compensate for IQ imbalance in the presence of CFO by using a known preamble of a repeated training sequence. In addition, the authors present a modified algorithm to suit the particular case when CFO is small. The performance of our proposed scheme has been examined with computer simulations on IEEE 802.11a signals. It is shown that the proposed method is more robust and renders better performance than the existing method.