A 40-GHz Series-Resonance VCO with Windmill-Coupled F-Type Inductive Network Achieving –132.36 dBc/Hz PN at a 10-MHz offset

This paper presents a series-resonance voltage-controlled oscillator (SR-VCO) featuring a windmill-coupled F-type (WCF) inductive network. The proposed WCF inductive network breaks the low-frequency limitation of conventional SR-VCOs, thereby extending the intrinsic low phase noise (PN) advantage of series-resonance operation to the millimeter-wave (mmWave) regime. The windmill-shaped coupling provides robustness against intra-core stage mismatches and improves area efficiency, while an inherent inductive voltage division avoids reliability issue without the frequency penalty associated with capacitive division. Fabricated in a 40-nm CMOS process, the prototype measures a frequency tuning range (FTR) of 38.08–42.19 GHz (10.2%) and a PN of –132.36 to –129.74 dBc/Hz at a 10-MHz offset, while consuming 40 mW from a 1-V supply, resulting in a peak figure of merit (FoM) of 188.3 dBc/Hz.