A Temperature Compensation Concept for a Micromachined Film Bulk Acoustic Resonator Oscillator

We present a temperature compensation technique of a film bulk acoustic resonator (FBAR)-based oscillator by tuning the supply voltage of the oscillator. The FBAR-based oscillator uses a high-Q FBAR that is made of a thin ZnO piezoelectric film sandwiched by two electrodes. The FBAR is significantly sensitive to temperature change, consequently resulting in large temperature sensitivity of the FBAR-based oscillator. In this paper, we present a temperature compensation technique that improves the temperature coefficient (TCf_osc) of a 1.625-GHz FBAR-based oscillator from -118 ppm/K to less than 1 ppm/K by tuning the supply voltage of the oscillator. The tuning technique has a large frequency tunability of -4305 ppm/V.