Improved noise reduction ability and frequency stability of VCO with external feedback loop

Abstract

This paper presents the integrated circuit combined with PI controller and the frequency to voltage converter (FVC) acting as the feedback part to be a closed-loop VCO circuit (CLVCO). The PI controller is designed by symmetrical optimum for optimum output response so as to minimize the effect of VCO noise. This closed loop circuit can achieve good frequency stability as well as good noise suppression. The experimental results show that CLVCO is independent from power supply variation and the frequency stability due to the effect of VCO noise or voltage drift which is greatly improved. © 2005 SICE.