Electronic system for measuring frequency in GHz range

Ultra-sensitive TFBAR (Thin Film Bulk Acoustic Wave Resonator) mass sensors can be used for the detection of dangerous substances. The chemically-sensitive part of such a sensor consists in a thin film of gold (Au) which covers the sensing area of the TFBAR and on top of which a layer of specific antibodies is deposited. TFBAR is a volume acoustic wave resonator that works in longitudinal vibration mode (thickness extension) and hence its resonance frequency is determined by the inverse of the piezoelectric layer thickness and directly proportional to the material dielectric constant. This paper presents the design and implementation of an electronic system based on a differential approach for measuring the chemical contamination-induced frequency deviation of a TFBAR sensor based on homodyne mixing of the output signals of two Pierce oscillators: a sensing one and a reference one.