This article presents a single-core broadband voltage-controlled oscillator (VCO), employing a dual-mode variable inductor (VID). By configuring two independent switched-capacitor arrays embedded into a magnetically coupled LC network with a moderately magnetic coupled coefficient, the frequency tuning range (FTR) is improved by the wide inductance reconfigurable range of the <inline-formula> <tex-math notation="LaTeX">{X} </tex-math></inline-formula>-type mode. Together with 2-bit conventional switched-capacitor banks, the VCO measures an FTR of 40.25% from 12.5 to 18.3 GHz. The low-quality factor (<inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula>) degradation characteristic of the <inline-formula> <tex-math notation="LaTeX">{L} </tex-math></inline-formula>-type mode is utilized to implement the tuning bands calibration (TBC). After calibration, the tuning voltage can always be calibrated within a small range around the common voltage. The ultimate turning band covers the frequency drift caused by the temperature variation. Designed and fabricated in 65-nm CMOS technology, the measured phase noise after 1/2 division is −114.7 dBc/Hz at 1-MHz offset from the 18.49-GHz carrier frequency. The VCO core exhibits average power dissipation of 9.6 mW from 0.75-V power supply and 0.053 mm2 die area, while the other circuits are powered by a 1.2-V supply.