Thickness Shear Acoustic Resonator With Transverse Reflectors Above 3 GHz
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Solution Overview
Problem
Conventional bulk acoustic wave and surface acoustic wave devices face limitations in extending their frequency range above 3 GHz, failing to achieve the required high electromechanical coupling coefficient and quality factor needed for 5G communication standards.
Innovation Solution
An acoustic resonator excited in a thickness shear mode, comprising an acoustic mirror, a piezoelectric layer made of single crystal lithium niobate or lithium tantalate, and transverse reflectors, with a specific configuration of electrode layers and materials to generate a shear mode mechanical wave, enhancing electromechanical coupling and quality factor at frequencies above 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional bulk acoustic wave and surface acoustic wave devices are used, then the operating frequency can be extended, but the electromechanical coupling coefficient and quality factor deteriorate above 3 GHz
Solution Approach 1:
The patent changes the vibration mode from conventional longitudinal or surface acoustic waves to thickness shear mode, and uses single crystal piezoelectric materials (lithium niobate or lithium tantalate) with specific crystal orientations to achieve high electromechanical coupling coefficient and quality factor at frequencies above 3 GHz
Solution Approach 2:
The patent employs composite structure combining single crystal piezoelectric materials with specific acoustic reflector layers to create a resonator that maintains high performance at millimeter wave frequencies, achieving both high operating frequency and high electromechanical coupling coefficient
2Volume of moving object
If the resonator size is reduced, then the device can be used in mobile phones and IoT devices, but the quality factor and signal-to-noise ratio may deteriorate
Solution Approach 1:
The patent transitions from two-dimensional surface acoustic wave propagation to three-dimensional thickness shear mode vibration, enabling compact device size while maintaining high quality factor through the thickness direction resonance
3Reliability
If the acoustic reflector layers are configured with specific impedance relationships, then the acoustic wave reflection is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by using alternating high and low acoustic impedance layers in the acoustic mirror, where each layer is specifically designed with particular impedance characteristics to achieve constructive interference and high reflection efficiency at the target frequency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables high-performance passband filters with improved electromechanical coupling and quality factor, supporting the new 5G communication standards and future upgrades by effectively operating at higher frequencies.
Implementation Method 1
the piezoelectric layer includes at least one of single crystal lithium niobate or single crystal lithium tantalate. The bottom electrode layer and the top electrode unit are configured to apply an electric field... generate a shear mode mechanical wave across a thickness of the entire piezoelectric layer
Implementation Method 2
The reflectors are transverse to the acoustic mirror placed beneath the piezoelectric layer, and the transverse reflectors are also arranged on the piezoelectric layer... configured to transversely reflect an acoustic wave
Implementation Method 3
The acoustic mirror includes at least one first acoustic reflective layer and at least one second acoustic reflective layer... acoustic impedance of each first acoustic reflective layer is less than the acoustic impedance of each second acoustic reflective layer
Data Source
AI summary
An acoustic resonator excited in a thickness shear modes includes an acoustic mirror, a bottom electrode layer, a piezoelectric layer, a top electrode unit, and transverse reflectors. The acoustic mirror comprises at least one first acoustic reflective layer and at least one second acoustic reflective layer, and the acoustic impedance of each first acoustic reflective layer is less than that of each second acoustic reflective layer. The bottom electrode layer is located on the acoustic mirror. The piezoelectric layer is provided on the bottom electrode layer. The top electrode unit is provided on the piezoelectric layer. The transverse reflectors are provided on the piezoelectric layer and comprises a first reflector located on the first side of the top electrode unit and a second reflector located on the second side of the top electrode unit, and the transverse reflectors are used for performing transverse reflection on the acoustic wave.