Application of active control technology for mass resolution improvement of FBAR

The mass resolution of the sensor based on a film bulk acoustic resonator (FBAR) needs to be improved when it is used to detect small molecules with low concentration. A method to improve the mass resolution of FBAR by active control technology is proposed. The active control function is realized by introducing an active control piezoelectric layer between the sensing piezoelectric layer and the substrate. During measuring, a specified control voltage is exerted onto the active control piezoelectric layer when a detecting voltage is exerted onto the sensing piezoelectric layer. The control voltage produces acoustic energy in the control piezoelectric layer to compensate the acoustic energy losses of the FBAR sensor, and the quality factor and mass resolution of the sensor are improved as the results. The mathematical model of the FBAR with active control function is established based on the continuum media theory. Numerical results show that the mass resolution of FBAR can be effectively improved by optimizing the amplitude and phase of the control voltage.