A 14-GHz-Band Harmonic Tuned Low-Power Low-Phase-Noise VCO IC with a Novel Bias Feedback Circuit in 40-nm CMOS SOI

In this paper, a harmonic tuned low-power low-phase-noise VCO IC with a novel bias feedback circuit is proposed. The transformer-based LC tank providing high impedance at the second and third harmonics is used to improve the phase noise performance. In addition, a novel feedback circuit is designed to suppress the gate-to-source voltage of the core transistors under their threshold voltage at the steady state while guaranteeing the robust start-up of the oscillation. The novel feedback circuit that requires no dc power supply can operate with an extremely small additional dc power consumption. The proposed VCO IC is designed, fabricated, and fully evaluated on-wafer in 40-nm CMOS SOI process. The proposed VCO IC has exhibited a measured best phase noise of -131.8 dBc/Hz at 10-MHz offset from the oscillation frequency of 14.94 GHz under a dc power consumption of only 1.4 mW.