Bilayer Lithium Niobate Acoustic Resonators for Spurious-Free Wideband Operation at 6 GHz
Abstract
The evolution of wireless communication standards toward higher frequencies and wider bandwidths places increasing demands on acoustic filter technologies. Conventional resonators face scaling limitations above 5 GHz, where lithographic constraints, reduced electromechanical coupling coefficient (k2eff), and spurious mode excitation hinder practical filter implementation. Here, we introduce a bilayer X-cut lithium niobate (LiNbO3) thickness-shear bulk acoustic resonator architecture that leverages symmetry engineering as a new design degree of freedom. By vertically stacking two piezoelectric thin films with a tailored bonding angle, the second-order thickness-shear mode (SH2, slow) is selectively excited. Furthermore, the fast thickness-shear modes inherent to X-cut LiNbO3 are suppressed, yielding a spurious-free in-band response. Devices operating around 6 GHz demonstrate a k2eff of approximately 35%, in close agreement with finite-element simulations and confirming the symmetry-driven mode selection mechanism. Proof-of-concept ladder filters demonstrate a fractional bandwidth of 18.6%, highlighting the wideband capabilities of the proposed architecture. The proposed configuration enables thickness-defined frequency scaling while maintaining high coupling and spectral purity, offering a promising platform for wideband radiofrequency filters in next-generation wireless systems.
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BibTeX
@misc{hartmann2026bilayer,
title = {{Bilayer Lithium Niobate Acoustic Resonators for Spurious-Free Wideband Operation at 6 GHz}},
author = {Florian Hartmann and Silvan Stettler and Luis Guillermo Villanueva},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.40044},
eprint = {2609.40044},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.40044},
}
RIS
TY - UNPB
TI - Bilayer Lithium Niobate Acoustic Resonators for Spurious-Free Wideband Operation at 6 GHz
AU - Florian Hartmann
AU - Silvan Stettler
AU - Luis Guillermo Villanueva
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.40044
UR - https://arxiv.org/abs/2609.40044
AB - The evolution of wireless communication standards toward higher frequencies and wider bandwidths places increasing demands on acoustic filter technologies. Conventional resonators face scaling limitations above 5 GHz, where lithographic constraints, reduced electromechanical coupling coefficient (k2eff), and spurious mode excitation hinder practical filter implementation. Here, we introduce a bilayer X-cut lithium niobate (LiNbO3) thickness-shear bulk acoustic resonator architecture that leverages symmetry engineering as a new design degree of freedom. By vertically stacking two piezoelectric thin films with a tailored bonding angle, the second-order thickness-shear mode (SH2, slow) is selectively excited. Furthermore, the fast thickness-shear modes inherent to X-cut LiNbO3 are suppressed, yielding a spurious-free in-band response. Devices operating around 6 GHz demonstrate a k2eff of approximately 35%, in close agreement with finite-element simulations and confirming the symmetry-driven mode selection mechanism. Proof-of-concept ladder filters demonstrate a fractional bandwidth of 18.6%, highlighting the wideband capabilities of the proposed architecture. The proposed configuration enables thickness-defined frequency scaling while maintaining high coupling and spectral purity, offering a promising platform for wideband radiofrequency filters in next-generation wireless systems.
ER -