A 37.5–45 GHz Superharmonic-Coupled QVCO With Tunable Phase Accuracy in 28 nm CMOS

This paper presents a new superharmonic coupling structure for millimeter-wave (mmW) quadrature voltage-controlled oscillators (QVCOs) with high phase accuracy and zero voltage headroom. The proposed coupling network can adjust the quadrature error with almost no phase noise penalty. A tail impedance theory for superharmonically coupled oscillators is introduced to analyze the locking mechanism, phase noise, phase accuracy, and phase tunability of the proposed superharmonic QVCO. For verification, a 40 GHz QVCO is fabricated in a 28 nm bulk CMOS process, which exhibits a phase noise of −94.32 dBc/Hz at 1 MHz offset and 0.18° quadrature error with 8.4 mW power consumption and 18.4% frequency tuning range.