Optimal block adaptive I/Q mismatch compensation based on circularity

Wireless systems frequently employ I/Q modulation techniques to achieve spectral efficiency for high data rate applications. However, the main drawback of I/Q downconversion is the amplitude and phase imbalances between the analog components in the I and Q branches of the receiver. The resulting I/Q mismatch is unavoidable for practical quadrature receivers and can be frequency-dependent in nature. In this paper, a novel Optimal Block Adaptive algorithm based on the circularity property is presented for frequency-dependent I/Q imbalance compensation. The proposed technique, called OBA-C, is based on the assumption that the received baseband signal deviates from circularity in the presence of I/Q mismatch. OBA-C uses the complex Taylor series expansion to optimally update the adaptive filter coefficients at each iteration, until the circularity of the received signal is restored. Simulation results confirm the remarkable improvement in I/Q mismatch compensation and convergence speed of the proposed technique as compared to another recently proposed circularity based method.