Design of an ultra-wideband 85.79 GHz 32 nm CNTFET current-starved ring VCO with −220.07 dBc/Hz FoM using the gₘ/ID approach

This paper presents a high-performance current-starved ring voltage-controlled oscillator (CSVCO) designed using carbon nanotube field effect transistors (CNT-FETs). A distributed variable capacitance scheme is employed to modulate the tuning voltage across individual oscillator stages, thereby significantly enhancing the oscillation frequency and tuning range while maintaining power efficiency and achieving a superior figure of merit (FoM). The design methodology, based on the transconductance-to-current efficiency ( \(gₘ/ID\) ) approach, provides a technology-independent framework for simplified sizing and biasing, improves power efficiency, and offers clear insight into device operating regions. The design is simulated using a 32 nm CNTFET technology node in the Cadence Virtuoso environment. The proposed CNT-FET-based current-starved ring VCO (CN-CSVCO) achieves an oscillation frequency of 85.79 GHz, a tuning range of 197.72 %, and consumes only 9.41 \(μ\) W of power at a control voltage of 0.4972 V. Furthermore, the design exhibits a phase noise of \(-\) 101.145 dBc / Hz and a FoM of \(-\) 220.07 dBc / Hz . These results demonstrate that CNT-FET-based VCOs can deliver high-frequency and energy efficiency, making them promising for next-generation millimeter-wave communication systems.