SAW Resonator Aperture Layout for Transverse Mode Suppression
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Solution Overview
Problem
Transverse resonance modes in surface acoustic wave resonators introduce sharp transmission zeros in the passband, reducing the performance of surface acoustic wave filters.
Innovation Solution
The surface acoustic wave resonator incorporates an interdigital electrode design with altered interdigital apertures and fractal bus bars to modulate the propagation direction of acoustic waves, suppressing transverse resonance modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric substrate is thinned to improve temperature compensation effect, then the temperature coefficient of the surface acoustic wave resonator is reduced, but transverse resonance modes are generated that introduce sharp transmission zeros in the passband
Solution Approach 1:
The patent applies local quality by making the interdigital apertures non-uniform, with different aperture sizes at different positions along the interdigital electrode. Specifically, the aperture width varies continuously or in steps from the input end to the output end, creating local variations in acoustic wave propagation characteristics that suppress transverse resonance modes while maintaining thin substrate geometry for temperature compensation
Solution Approach 2:
The patent changes the geometric parameter of the interdigital apertures (width, shape, or position) along the length of the electrode. By gradually or progressively modifying the aperture dimensions, the acoustic wave propagation parameters are altered to suppress transverse modes. This parameter variation allows the thin substrate to maintain both temperature compensation and reduced transverse resonance
2Manufacturing precision
If the thickness of the piezoelectric substrate is reduced to less than 10λ for better temperature compensation, then temperature coefficient is reduced, but transverse resonance modes are excited that reduce filter performance
Solution Approach 1:
The interdigital electrode structure implements local quality through position-dependent aperture characteristics. The apertures are designed with varying dimensions along the electrode length, creating localized acoustic impedance variations that prevent the excitation of transverse resonance modes while allowing the substrate to be sufficiently thin for precise temperature coefficient control
Solution Approach 2:
The patent introduces asymmetry in the interdigital aperture design, where the aperture width or shape differs between the input and output regions of the electrode. This asymmetric configuration disrupts the symmetry required for transverse resonance mode formation, thereby suppressing these harmful modes while maintaining the thin substrate necessary for accurate temperature compensation
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 modified resonator effectively reduces transverse resonance modes, enhancing the performance of surface acoustic wave filters by minimizing sharp transmission zeros.
Implementation Method 1
Due to piezoelectricity of the piezoelectric substrate, the input electrical signal is converted into acoustic waves and then converted back to another electrical signal in the surface acoustic wave resonator
Implementation Method 2
a surface acoustic wave resonator arranged on the piezoelectric substrate. The surface acoustic wave resonator operates substantially on a basis of a following process. An electrical signal is inputted into the surface acoustic wave resonator. Due to piezoelectricity of the piezoelectric substrate, the input electrical signal is converted into acoustic waves
Data Source
AI summary
A surface acoustic wave resonator, comprising: an interdigital electrode comprising a first bus bar and a second bus bar. The first bus bar connects first fingers and second pseudo-fingers alternately arranged in a first direction, and the second bus bar connects second fingers and first pseudo-fingers alternately arranged in the first direction. Each first finger extends along a same straight line and is spaced apart from its corresponding first pseudo-finger. Each second finger extends along a same straight line and is spaced apart from its corresponding second pseudo-finger. In each pair of adjacent first and second fingers, a distance between an end of the first finger away from the first bus bar and an end of the second finger away from the second bus bar is an interdigital aperture. At least a part of the interdigital apertures formed among the first fingers and the second fingers are different.