A millimeter-wave CMOS VCO using a TL inductor with digitally controllable artificial dielectrics

A 36 GHz LC-VCO with a digitally controllable transmission line (TL) inductor is presented in this work. The isolated metal strips used as artificial dielectrics are adopted underneath the inductor in the oscillator to enhance the effective permittivity and reduce substrate loss. Meanwhile, the potential of a portion of the metal strips are designed to be digitally controllable to vary the parasitic capacitance of the TL inductor. Thus, the entire frequency tuning range of the VCO adopting the TL inductor with digitally controllable artificial dielectrics can be extended. The increment of frequency tuning range introduced by the proposed technique depends on the amount and layer of the metal strips which are designed to be digitally controllable. The proposed VCO was fabricated using 0.13 μm CMOS RF technology. The measured operation frequency ranges from 36.01 to 36.71 GHz. The measured phase noise ranges from -93.66 to -101.7 dBc/Hz at 3 MHz offset. The entire circuit, including two output buffers, consumes 18 mW power under 1 V supply. The measured output spectrum of the VCO is higher than -13.3 dBm across the entire oscillation frequency band. The calculated FoM is 171.