A high frequency stability of VCO with dual feedback loop

Abstract

This paper is purposed to improve the high frequency stability of the voltage controlled oscillator (VCO) with dual feedback loop. The proposed of closed loop VCO (CLVCO) is composed of PI controller in the forward part and in the feedback part the phase locked loop is used instead of a frequency to voltage converter (FVC) for some advantages, there is no need for a large frequency division element (1/N) in the feedback part. The other advantages of phase-locked loop is used as the feedback element, the high frequency bandwidth of a closed loop VCO is possibly designed. The CLVCO can greatly improved VCO characteristic such as faster speed response as well as higher operation bandwidth, to minimize the effect of the VCO noise and the power supply variation and also obtain better linearity of VCO output. The experimental results confirm the validity of the proposed CLVCO. © 2005 SICE.