Phase noise degradation at high oscillation amplitudes in LC-tuned VCO´s

This paper deals with the Single Sideband to Carrier Ratio (SSCR) dependence on the oscillation amplitude of a fully integrated LC-tuned voltage-controlled oscillator, fabricated in high-speed bipolar technology. As the oscillation amplitude increases, the SSCR reaches a minimum and then steeply rises, setting a limit to the range where better performance can be traded against higher power dissipation. This dependence is fully explained by taking into account that noise and disturbances modulate the phase delay due to the active elements. Experimental and simulation procedures for the evaluation of this effect are presented and their impact on the circuit performance is discussed.