Scale Interdigital Transducer-Based Microacoustic Resonators Into mmWave Applications.

Area of Science:

• Materials Science
• Electrical Engineering
• Acoustics

Background:

• Lamb wave mode resonators utilizing Lithium Niobate (LiNbO3) thin films and interdigital transducers (IDTs) are crucial for miniaturized millimeter wave (mmWave) acoustic filters due to high electromechanical coupling and phase velocities.
• Electromagnetic (EM) self-resonances, caused by the interaction of static capacitance and self-inductance in $50~\Omega $ systems, pose a significant challenge for higher-order Lamb wave modes in mmWave applications, degrading resonator performance.
• Existing modeling methods are insufficient for analyzing the EM-acoustic coupling in the 5G/6G mmWave spectrum, necessitating new approaches.

Purpose of the Study:

• To propose novel design philosophies for IDTs aimed at reducing self-inductance for mmWave applications.
• To investigate the complex interactions between acoustic and electromagnetic waves within IDTs.
• To develop new equivalent circuit models capable of analyzing EM-acoustic coupling in various scenarios for mmWave devices.

Main Methods:

• Development of new design strategies for IDTs to minimize self-inductance.
• Exploration of the coupled acoustic and EM wave phenomena within IDTs.
• Introduction of advanced multiphysic equivalent circuit models for accurate device simulation.
• Fabrication of experimental devices using Y-128° cut LiNbO3 thin films for validation.

Main Results:

• The proposed IDT design philosophies effectively reduce self-inductance, mitigating unwanted EM self-resonances.
• The new equivalent circuit models accurately predict device behavior, demonstrating strong correlation between simulation and experimental outcomes.
• The study validates the efficacy of the developed methods for mmWave acoustic filter applications.

Conclusions:

• The developed multiphysic equivalent circuit models and IDT design strategies enable the effective utilization of acoustic resonators in the mmWave range.
• This work addresses the critical bottleneck of EM-acoustic coupling, allowing for necessary static capacitance without performance degradation.
• The findings facilitate the advancement of high-performance acoustic filters and frequency references for next-generation wireless communication systems.