ML estimation of receiver IQ imbalance parameters

In this paper, we address the in-phase (I) and quadrature (Q) imbalance estimation and compensation at the receiver stage of modern communication systems. Low-cost fabrication technologies and high data-rate transmissions render the conventional receivers very sensitive to the imperfections of their analog stage and, hence, proper countermeasures need to be adopted. Since the IQ imbalance can be completely compensated provided that the IQ parameters are known at the receiver stage, in this paper we address the blind estimation of such parameters. According to the maximum likelihood (ML) criterion, we derive the optimum blind estimator for a QAM transmission as well as for a circularly symmetric Gaussian one and, therefore, we evaluate, by means of computer simulations, their performances in terms of mean square estimation error.