Abstract
A differential series-resonance voltage-controlled oscillator (SR-VCO) is proposed in this paper for ultra-low phase noise applications. This SR-VCO utilizes transformer-based series-resonant tanks with small coupling coefficients to eliminate mode ambiguity, enabling two-stage differential oscillation instead of conventional four-stage quadrature structures. Based on a 65 nm CMOS technology, a differential SR-VCO is designed, which achieves a frequency tuning range of 8.79–10.34 GHz (16% relative bandwidth). In this frequency band, the phase noise of the SR-VCO changes from -125.8 dBc/Hz to -128.7 dBc/Hz at 1 MHz offset. And the designed SR-VCO consumes a power of 135 mW under a 1.2 V supply.