A Tunable Dual-mode Lamb Wave Resonator with Floating Electrodes

In this paper, we present a tunable dual-mode Lamb wave resonator (LWR) based on Aluminum nitride thin films. The dual-mode LWR consists of floating electrodes positioned between interdigital electrodes (IDTs), which results in two resonant peaks, operating at 1.69GHz and 1.757 GHz when the height (H) of floating electrodes is $0.05 \mu \mathrm{m}$ and the width W is $0.7 \mu \mathrm{m}$, respectively. The resonant frequency and impedance ratio of the two peaks are tuned by the size of the floating electrodes. When the H is from $0.05 \mu \mathrm{m}$ to 0.25 $\mu \mathrm{m}$ and the W is $0.7 \mu \mathrm{m}$, the distance between the two peaks $(\Delta f)$ is adjusted from 67MHz to 455MHz. Furthermore, as W increases, the impedance ratio of the first peak is amplified while the second peak is attenuated. The coupling strength of the two peaks is close to that of conventional single-peak resonators. The tunable LWR with optimized floating electrodes shows great potential in fabricating high-frequency dual-passband filters.