Longitudinal wave resonant frequency calculation and verification of the bulk acoustic resonator
The rapid development of wireless communication technology and the clear trend of higher frequency, miniaturization, and integration of RF components have provide opportunities through the research and production of thin film bulk acoustic resonators (TFBAR). In the design of TFBAR products, how to determine the frequency is always the starting point. The thickness-extension type of resonators can produce higher frequency, as it has been proven through products on the market. For the thickness-shear types of resonators, precise calculation of vibration frequency is important in the design. We established a vibration model of TFBAR and obtained the frequency equation based on the layered infinite plates. The frequency equation can be used to evaluate a design, or select structural parameters based on the given frequency. Our frequency equation has been validated with experimental data.