VOLTAGE-CONTROLLED OSCILLATOR DESIGN USING FERROELECTRIC VARACTORS

ABSTRACT Ferroelectric capacitors made from Ba1−xSrxTiO3 (BST) are applied as varactors in tunable, high frequency circuit applications. In this context, a voltage-controlled oscillator (VCO) is studied. VCOs are integral parts of phase locked loops, clock recovery circuits and frequency synthesizers and thus are widely used in both discrete and on-chip applications. Ferroelectric varactors are capable of out-performing solid-state varactors at microwave frequencies, due to their lower parasitic series resistance that leads to a higher Q-factor. In VCO implementations, this higher Q leads in turn to lower phase noise, a critical quality for these circuits. A VCO design is presented and the performance of ferroelectric varactors is compared with solid-state varactors.