Blind I/Q Skew Estimation and Compensation by Exploiting Channel Frequency Selectivity

In this letter, a blind timing skew estimation and compensation scheme is proposed to calibrate the in-phase and quadrature (I/Q) branches for wideband direct conversion receivers. The proposed scheme first selects a subset of mirror-frequency pairs with different powers arising from experienced channel frequency selectivity, and then estimates the I/Q timing skew using the second-order statistics (SOS) of the selected frequency components. To further mitigate the I/Q distortion, frequency domain compensation can be performed over each pair of mirrored frequencies using the estimated timing skew. As the proposed scheme does not rely on any pilot symbol or training sequence, it can be performed during regular traffic without sacrificing any bandwidth efficiency. Simulation results validate the efficacy of the proposed scheme compared to the ideal case with zero I/Q skew and the case without I/Q skew compensation.