Design and modeling of film bulk acoustic resonator considering temperature compensation for 5G communication

Abstract

The new generation of communication systems requires radio frequency (RF) filters with better performance indicators, and traditional RF filters can no longer satisfy the requirements of increasingly sophisticated wireless communication equipment. Piezoelectric Film bulk acoustic resonators (FBARs) have gradually become a focus of communication system research. In this study, the temperature effect was considered in the FBAR electrical model. SiO₂ with a positive temperature coefficient was placed under the bottom electrode to perform temperature compensation. COMSOL software was used to study the shape of the electrode of the FBAR unit, the irregular shape of the electrode could obtain a smoother resonant frequency curve, and the common cavity and back erosion structure of the FBAR unit were studied, to extract the corresponding dielectric loss and mechanical loss of the piezoelectric layer, and to optimize the one-dimensional electrical model further. The optimized electrical model was used to design an FBAR filter. The center frequency was 3.52 GHz, the bandwidth was 115 MHz, the insertion loss was 0.87 dB, the in-band ripple was 1.32 dB, the out-of-band rejection was better than − 40 dB, and the absolute value of temperature coefficient of frequency was 7.09 ppm/°C, basically achieving the expected performance, which can be applied to the design of RF filters in mobile phones and other wireless terminals where the temperature requirement is harsh, and provides a solution for frequency selection and control in the field of high frequency communication.