WE 3 C - 3 Tracking Phaselock Loop Characteristics with a VCO Using a Barium Strontium Titanate ( BST ) Thin

Barium Strontium Titanate (BST) varactors utilized in a VCO demonstrate unique tuning characteristics compared to junction varactors. A 2.7 GHz microstrip line VCO operates in a tracking phaselock loop configured as an X4 frequency multiplier. BST oscillator tuning and the effect on loop dynamics is observed by the intentional design of an under damped system. Oscillator noise correction and peaking is noted particularly at low tune voltages. Loop dynamics are addressed through proper design of the loop compensator filter. The differences between BST varactor and junction varactor operation in frequency control are noted. Index Terms BST, VCO, PLL, loop filter, tracking loop, ferroelectric, resonator.