{
  "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.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.40044",
  "author_total": 3,
  "authors": [
    {
      "name": "Florian Hartmann"
    },
    {
      "name": "Silvan Stettler"
    },
    {
      "name": "Luis Guillermo Villanueva"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6zcppgnw6m5xe.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.40044",
  "fulltext_url": null,
  "id": "6zcppgnw6m5xe",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.40044",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.app-ph"
    ],
    [
      "openalex",
      "2204|Acoustic Wave Resonator Technologies"
    ]
  ],
  "openalex": "W7215076054",
  "pdf_url": "https://arxiv.org/pdf/2609.40044",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6zcppgnw6m5xe.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:49Z",
      "native_id": "2609.40044",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.40044"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.app-ph",
      "subfield": "applied-instrumentation"
    }
  ],
  "title": "Bilayer Lithium Niobate Acoustic Resonators for Spurious-Free Wideband Operation at 6 GHz",
  "title_text": "Bilayer Lithium Niobate Acoustic Resonators for Spurious-Free Wideband Operation at 6 GHz",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:49Z",
  "url": "https://research.draconitic.com/paper/6zcppgnw6m5xe",
  "venue": "arXiv",
  "versions": []
}