A 1V Dual-Band VCO Using an Integrated Variable Inductor

An integrated variable inductor is proposed using an on-chip transformer to obtain 2 inherent resonant modes for band-switching applications. Employing such a variable inductor in a 0.18-μm CMOS process at a 1-V supply, a VCO is demonstrated to oscillate in 2 distinct frequency bands from 2.2 GHz to 3.6 GHz and from 10.7 GHz to 11.3 GHz. The VCO measures phase noise of around -135.5 dBc/Hz for the lower band and around -126.5dBc/Hz for the upper band at 10-MHz offset while consuming 5mW and occupying an area of 0.4×0.8 mm2.