P1.24 A Voltage Controlled Oscillator Using Barium Strontium Titanate (BST) Thin Film Varactor

Abstract — Barium Strontium Titanate (BST) has a field-dependent permittivity and can be used as a dielectric in voltage tunable capacitors or varactors. These BST-based varactors are passive devices and have significantly different properties compared to semiconductor varactors. A voltage tunable oscillator using a BST thin film varactor was designed and characterized. The frequency of oscillation varied from 34.8MHz to 44.5 MHz (28 % tuning) upon application of 7 volts tuning voltage. The VCO gain was 1.38MHz/V and the 2 nd harmonic was over 23dB below the fundamental throughout the tuning range. Index Terms — Voltage controlled oscillator, varactors, ferroelectric films, harmonic distortion