Dual-Path $LC$ VCO Design With Partitioned Coarse-Tuning Control in 65 nm CMOS

This letter describes a dual-path LC voltage controlled oscillator (VCO) design that reduces both coarse-tuning and fine-tuning sensitivities. By using a combination of discrete and continuous tuning methods for the coarse-tuning control, a very high gain ratio between the coarse-tuning path and the fine-tuning path can be avoided, significantly alleviating noise and coupling problems due to high coarse-tuning gain. A 3.03-3.67 GHz dual-path VCO in 65 nm CMOS exhibits -120.7 dBc/Hz at a 400 kHz offset from a 1.73 GHz carrier, showing better performance than the conventional single-path VCO that is implemented for comparison.