CRLB and ML algorithm for joint recovery of carrier phase and IQ imbalance

Due to the challenging design goals for present and future communication systems, e.g., low cost and small power dissipation, direct-conversion or low-IF transceivers are a most attractive option, preferably realized on a single-chip architecture. The inherent drawbacks, like IQ gain and phase imbalance, can be compensated by appropriately developed DSP solutions. In this respect, Cramer-Rao lower bound (CRLB) and maximum-likelihood (ML) algorithm for joint recovery of carrier and IQ phase offset are very interesting for comparison reasons. Interestingly, recent contributions on this subject do not address this issue, whereas it has been discussed in a less recent paper. The current investigation extends the latter in two aspects: (i) it includes IQ gain imbalance as well; (ii) the correlation of noise components in the baseband, regarded as independent in the reference paper and thus causing some shortcomings, is taken into account.