Membrane Longitudinal Resonator for High-Frequency Mode Suppression
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Solution Overview
Problem
Microacoustic filters face challenges in operating effectively at high frequencies above 3 GHz due to fabrication issues and parasitic effects, particularly with surface acoustic wave (SAW) modes.
Innovation Solution
The implementation of a membrane-type longitudinal mode microacoustic resonator with a specific Euler angle configuration for the piezoelectric layer, combined with an air gap structure, to selectively excite high-velocity longitudinal modes and suppress shear horizontal modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If surface acoustic wave (SAW) modes are used in microacoustic filters, then the filters can operate at high frequencies, but fabrication issues and parasitic effects occur above 3 GHz
Solution Approach 1:
The patent changes the acoustic mode parameter from surface acoustic wave (SAW) mode to bulk acoustic wave (BAW) mode, specifically using longitudinal modes. This parameter change enables operation at frequencies above 3 GHz while avoiding the fabrication issues and parasitic effects that plague SAW modes at these frequencies. The bulk mode operation fundamentally alters how acoustic waves propagate through the piezoelectric layer, eliminating the surface-related problems.
2Ease of manufacture
If conventional piezoelectric orientations are used, then manufacturing is simpler, but shear horizontal modes are not suppressed and acoustic energy confinement is poor
Solution Approach 1:
The patent specifies precise Euler angle parameters for the piezoelectric layer orientation: λ=90°±1.5°, μ=90°±1.5°, θ=40°±1.5°. These parameter specifications simultaneously achieve two goals: they provide a clear fabrication target for manufacturing while enabling effective suppression of shear horizontal modes and improving acoustic energy confinement. The specific angular parameters optimize the piezoelectric coupling for longitudinal modes while minimizing excitation of unwanted shear modes.
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
This configuration improves the confinement of acoustic energy, reduces parasitic modes, and enhances the performance of microacoustic resonators in wireless communication filters, particularly in the frequency range of 2.5 GHz to 6 GHz.
Implementation Method 1
Using a piezoelectric material as a vibrating medium, acoustic resonators operate by transforming an electrical signal wave that is propagating along an electrical conductor into an acoustic wave that is propagating via the piezoelectric material.
Implementation Method 2
an electrode structure comprising an interdigital transducer disposed on the first surface of the piezoelectric layer
Data Source
AI summary
Methods, apparatuses, and other aspects are disclosed for microacoustic resonators. In one aspect, an apparatus includes a temperature compensation layer comprising a first surface and a second surface opposite the first surface, and a piezoelectric layer having a first surface and a second surface opposite the first surface, where the piezoelectric layer is disposed on the first surface of the temperature compensation layer with the second surface of the piezoelectric layer facing the first surface of the temperature compensation layer, and where the piezoelectric layer has an orientation configured to excite a longitudinal mode. The apparatus further includes an electrode structure comprising an interdigital transducer disposed on the first surface of the piezoelectric layer, where the second surface of the temperature compensation layer faces an air gap.