Design and Analysis of a Low-Power 30/60 GHz Dual-Band CMOS Voltage-Controlled Oscillator (VCO) Using B-to-GND-with-RB Varactors

This paper presents a low-power 30/60 GHz dual-band CMOS voltage-controlled oscillator (VCO) for 5G applications. The design employs an LC-VCO core that simultaneously generates differential fundamental-frequency outputs and a single-ended second-harmonic output. To improve second-harmonic spectral purity, a second-harmonic quarter-wavelength (λ/4) transmission line is inserted in the VDD bias path of the VCO core. A body-to-ground-with-resistor (B-to-GND-with-RB) NMOS varactor configuration is adopted to provide a wide, monotonic tuning range while suppressing substrate leakage and noise coupling. In addition, a fundamental-frequency λ/4 transmission line is introduced in the control-voltage bias path to improve AC grounding of the differential varactor center node. The VCO consumes 2.19 mW and achieves a tuning range of 24.59–30.5 GHz (21.5%). At 27.48 GHz, it exhibits a phase noise of −117.69 dBc/Hz at a 10 MHz offset, corresponding to a figure of merit (FoM) of 189.72 dBc/Hz. The second-harmonic output covers 49.18–61 GHz, with the same fractional tuning range. The VCO core occupies a compact chip area of only 0.021 mm2.