Modeling of inter-digitated transducer for high-order contour mode resonators

LiNbO₃ contour-mode resonators (CMR) have the potential to fulfill the requirement of multi-frequency wide-bandpass filters. For CMRs, the position of the inter-digitated transducer (IDT) fingers can significantly affect their performance [1], as the reflection of acoustic waves at the sharply defined mechanical boundaries cause strong interferences of these waves. In this paper, we present a model that analytically & intuitively explains the behavior of CMRs with IDT at the mechanical anti-nodes (AN) of the targeted mechanical mode vs. with IDT at the nodes (N). The model is then verified with experimental results.