A Mixer-BBPD-Based Real-Time I/Q Calibration Loop for High-Speed Ring-Oscillators

This paper proposes a digital-intensive real-time in-phase/quadrature (I/Q) calibration loop for mm-wave ring-oscillators (ROs) by adopting a fully-symmetric mixer-based bang-bang phase detector (BBPD). The proposed calibration loop is both area- and power-efficient, making it highly suitable for on-chip integration. Implemented in $28-\text{nm}$ CMOS, the proposed automatic I/Q calibration achieves high accuracy $\lt0.5^{\circ}$ for an RO operating at 28 GHz.