A technique to extend tuning range of high frequency quadrature VCO

A new approach to extend the tuning range of high frequency quadrature VCO has been proposed. The method exploits the existence of two possible modes of operation, with distinct frequencies, in LC QVCOs based on a pair of coupled cores. Mode switching is achieved by choosing between two types of reactive degeneration in coupling transistors. Used along with varactor control-based continuous tuning, in an implementation in 0.13um CMOS process, the technique extends tuning range by more than 85% over varactor-only based approach at similar oscillation frequency, phase noise, power and quadrature accuracy. This method also has limited noise degradation across the entire tuning range and requires fixed amount of power for all frequencies. Cons timing a total current of 11mA from 1.2V supply the QVCO exhibits simulated phase noise of -104.7 to -106.6dBc/Hz at 1MHz offset from center frequency. The tuning range is from 17.78 to 20.64-GHz.