A Gigahertz-range High-Q VCO

Abstract

This thesis presents the theory, design, and measurements of two fully monolithic voltage-tunable above-IC-FBAR oscillators for 2.1 GHz in 0.25-μm SiGe BiCMOS technology. The narrow-band FBAR devices were built above the SiGe circuits during post-processing steps. The oscillators are based on a two-transistor loop structure and use the above-IC FBAR in its series-resonant mode. One of the oscillators has a single-ended output, and the other one is implemented with a differential output. The oscillators show a significant improvement in phase noise performance compared to a reference LC VCO fabricated in the same process, with the best phase noise being -144.1 dBc/Hz at an offset of 1 MHz and -149.6 dBc/Hz at 3 MHz. The architecture offers advantages in overcoming frequency tuning difficulties usually present when using high-Q resonators. Although the used frequency tuning solution compromises phase noise performance, the measured tuning range of 37 MHz is the highest yet reported for FBAR oscillators. /Kir09