A −189 dBc/Hz FOMT wide tuning range Ka-band VCO using tunable negative capacitance and inductance redistribution

An ultra wideband LC voltage-controlled oscillator (LC-VCO) operating in the Ka-band with equally spaced sub-band coarse tuning characteristics is proposed and characterized. A tunable negative capacitance (TNC) circuit technique is used to cancel the fixed capacitance in the LC-tank to extend the tuning range (TR). A digitally-switched varactor coarse tuning structure with an inductance redistribution technique is utilized to reduce VCO gain (K_V) and retain uniform spacing between tuning curves. The proposed VCO structure and a baseline VCO are fabricated in a 130 nm CMOS process. Compared to the reference VCO, the proposed VCO achieves a 34% increase in TR with maximum K_V of 450 MHz/V. The measured worst-case phase noise is -100.1 dBc/Hz at 1 MHz offset across the TR from 30.5 GHz to 39.6 GHz. The power dissipation of the VCO core is 11 mW from a 1.2 V supply. The TNC-based VCO achieves a FOM_T of -189 dBc/Hz, which is the highest reported at the Ka-band.