Enhancement of surface acoustic wave harmonics excitation using bonded dissimilar-material structures and its application to next-generation super-high frequency filters

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02181
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: University of Yamanashi
• Principal Investigator: Shoji Kakio 山梨大学, 大学院総合研究部, 教授 (70242617)
• Co-Investigator(Kenkyū-buntansha): 水野 潤 早稲田大学, ナノ・ライフ創新研究機構, 客員上級研究員(研究院客員教授) (60386737) ; 鈴木 雅視 山梨大学, 大学院総合研究部, 助教 (60763852)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: SAWフィルタ / 高周波化 / 異種材料接合 / 高調波

Outline of Final Research Achievements

For the evolution of next-generation mobile communication systems, surface acoustic wave (SAW) devices with higher frequency and wide bandwidth are strongly demanded. The conventional SAW devices have a frequency limit of around 3.5 GHz owing to the limitations of narrower electrodes and power handling capability. In this study, the enhancement of high-order SAW harmonics by increasing the metallization ratio was theoretically and experimentally investigated in high-performance bonded dissimilar-material structures, such as LiTaO3(LT)/quartz and LiNbO3(LN)/quartz. It was clarified that the 3rd and 5th harmonics of the SAW are strongly excited compared to a single LT or LN, resulting in significantly larger resonance characteristics. The applicability to ultra-high frequency filters that can operate at frequencies 3 and 5 times higher without narrowing the electrode period was demonstrated.

Free Research Field

通信工学，超音波エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

スマートフォン等の端末用の弾性表面波(SAW)フィルタには，LiTaO3(LT)やLiNbO3(LN)の圧電結晶が用いられてきたが，第5世代通信システム，次世代通信システムの高周波化に必要な電極周期の狭小化は限界である．本研究では，LT薄板，またはLN薄板を水晶基板と異種材料接合させた構造と，0.8程度の電極メタライゼーション比を組み合わせると，単体のLT，またはLNと比較してSAWの3次，5次高調波が強勢に励振され，格段に大きな共振特性が得られることを理論的，実験的に明らかにし，電極周期を狭くすることなく3倍，5倍の周波数で動作可能な超高周波フィルタへの適用可能性を示した．