Guided SAW Resonator Wave Apodization for Spurious Mode Suppression
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Solution Overview
Problem
Acoustic wave devices, particularly surface acoustic wave (SAW) resonators, face challenges in reducing spurious modes while maintaining high quality factor, electromechanical coupling coefficient, and compact size due to the limitations of conventional apodization techniques which often degrade performance.
Innovation Solution
The implementation of an interdigital electrode structure with apodization edges in a wave pattern, such as sinusoidal patterns, to reduce spurious modes while maintaining high quality factor and electromechanical coupling coefficient, and allowing for a smaller device size by optimizing the wave pattern's amplitude and period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional apodization techniques are used to reduce spurious modes, then spurious modes are reduced, but quality factor and electromechanical coupling coefficient are degraded
Solution Approach 1:
The patent applies curvature by using sinusoidal wave patterns for the apodization edges of the interdigital electrode structure instead of conventional straight or linear transitions. This curved geometry smoothly varies the electrode finger width and spacing, reducing spurious modes while maintaining the desired acoustic wave propagation characteristics and preserving quality factor and electromechanical coupling coefficient.
Solution Approach 2:
The patent changes the geometric parameters of the apodization edges by defining them with sinusoidal functions that control the gradual variation of electrode dimensions. By optimizing the amplitude and wavelength of these sinusoidal patterns, the invention achieves effective suppression of spurious modes while maintaining high quality factor and electromechanical coupling coefficient through controlled parameter variation.
2Object-generated harmful factors
If conventional apodization techniques are used to reduce spurious modes, then spurious modes are reduced, but device size increases
Solution Approach 1:
The sinusoidal wave pattern provides a compact curved transition zone that achieves effective apodization within a smaller area compared to conventional linear apodization. The curved geometry allows the electrode fingers to gradually change dimension over a shorter distance, reducing the overall device footprint while still suppressing spurious modes effectively.
Solution Approach 2:
By optimizing the amplitude and wavelength parameters of the sinusoidal apodization pattern, the invention achieves effective spurious mode suppression within a compact area. The parameter optimization allows the apodization transition to occur more efficiently, reducing the space required while maintaining the desired acoustic wave control and suppressing unwanted modes.
3Volume of moving object
If the interdigital electrode structure is made compact to reduce device size, then device size is reduced, but spurious modes increase
Solution Approach 1:
The sinusoidal wave pattern enables effective apodization within a compact area by using curved geometry to gradually vary electrode dimensions. This curved transition zone achieves smooth impedance matching and wave control in a smaller space, preventing spurious mode generation even in compact device configurations where conventional linear apodization would fail.
Solution Approach 2:
The invention uses optimized sinusoidal parameters (amplitude and wavelength) to achieve effective spurious mode suppression within a compact footprint. The parameter optimization allows the apodization function to be performed efficiently in reduced space, maintaining acoustic wave control and suppressing unwanted modes despite the smaller device size.
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 approach effectively reduces spurious modes, enhances quality factor and electromechanical coupling coefficient, and allows for a smaller device size by optimizing the wave pattern's characteristics, leading to improved performance compared to conventional SAW resonators.
Implementation Method 1
Piezoelectric materials acquire a charge when compressed, twisted, or distorted, and similarly compress, twist, or distort when a charge is applied to them. Accordingly, when an alternating electrical signal is applied to the one or more electrodes in contact with the piezoelectric material, a corresponding mechanical signal (i.e., an oscillation or vibration) is transduced therein.
Implementation Method 2
surface acoustic wave (SAW) resonators, which are increasingly used to form filters used in the transmission and reception of radio frequency (RF) signals for communication
Data Source
AI summary
An acoustic resonator includes a piezoelectric layer on a substrate and an interdigital electrode structure on the piezoelectric layer. The interdigital electrode structure includes a first bus bar, a second bus bar, a first set of electrode fingers, and a second set of electrode fingers. The first bus bar and the second bus bar extend parallel to one another along a length of the interdigital electrode structure. The first set of electrode fingers are coupled to the first bus bar and extend to a first apodization edge. The second set of electrode fingers are coupled to the second bus bar and extend to a second apodization edge. The first set of electrode fingers and the second set of electrode fingers are interleaved. At least one of the first apodization edge and the second apodization edge provides a wave pattern along the length of the interdigital electrode structure.