A wideband Colpitts VCO with 30% continuous frequency tuning range using a tunable phase shifter

A wideband Colpitts VCO using an analog tunable phase shifter as the frequency tuning component is presented. The tunable phase shifter is used as the resonator in a common collector Colpitts oscillator. An inductor is added in series with one of the feedback capacitors to avoid oscillation at higher order resonances of the phase shifter. The proposed VCO has a measured continuous frequency tuning range of 30% from 569 MHz to 767 MHz, and a measured phase noise between -117 dBc/Hz and -124 dBc/Hz at 1 MHz offset.