PM and AM noise in voltage controlled oscillators

An approach to PM and AM noise calculation in oscillator with voltage controlled oscillations frequency (VCO) is developed. It is based on quasi-steady state equations of the oscillator. Both wideband and 1/f noise sources are taken into consideration. Under several assumptions simple formula for PM noise in VCO is obtained and discussed. An influence of feedback through unbypassed emitter resistance R_e on PM and AM noise of the oscillator is investigated and optimal values of R_e, providing minimal values of PM noise due to wideband and 1/f noise sources are found. Dependencies of PM noise in VCO on the oscillations amplitude are discussed theoretically and investigated in experimental VCO. The ways to decrease PM noise of the VCO that follow from main results of the paper are discussed.