High-Efficiency Class-C <inline-formula> <tex-math notation="LaTeX">$LC$ </tex-math> </inline-formula>-VCO With AFC-Based Phase Noise Compensation

Abstract

A 4.1–5-GHz voltage-controlled oscillator (VCO) with phase noise insensitive to equivalent resistance ${R} _{\mathrm {p}}$ is presented in this letter. A self-adjusted current resource (SACR) is implemented to alleviate the phase noise deterioration, while the control logic of SACR is compatible with autofrequency calibration resulting in no additional hardware overhead and power. Based on the equivalent internal resistance of the resonant cavity increases with oscillation frequency, the SACR can improve the phase noise and power efficiency. Fabricated in a 180-nm 1P9M CMOS technology, the SACR is employed inside a 4-bit switching capacitance VCO resulting in a tuning range of 4.1–5 GHz and the corresponding phase noise between −124.67 and −128.04 dBc/Hz at a 1-MHz offset. The phase noise is improved by 2.09 dB at 4.1 GHz with SACR.