Tilted IDT Electrode Layout for Acoustic Filter Stopband Control
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Solution Overview
Problem
Existing acoustic wave filters, particularly those with multi-layer piezoelectric substrates, suffer from transverse mode spurious responses and slanted stopbands due to tilted interdigital transducer (IDT) electrodes, which degrade filter performance and accuracy.
Innovation Solution
The use of a tilted IDT electrode with increased thickness and pitch modulation, along with a non-zero tilt angle, to suppress transverse modes and shift the stopband to outside the frequency range of interest, thereby improving frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tilted IDT electrode is used to suppress transverse modes, then transverse mode spurious responses are reduced, but slanted stopbands are introduced that degrade filter performance
Solution Approach 1:
The patent applies asymmetry by intentionally introducing a tilt angle to the IDT electrode structure. This asymmetric configuration suppresses transverse mode spurious responses by disrupting the symmetry that would otherwise support these unwanted modes, while the tilt angle is carefully controlled to avoid creating harmful slanted stopbands.
Solution Approach 2:
The patent employs parameter changes by optimizing the tilt angle of the IDT electrode within a specific range (0° to 10°, preferably 2° to 5°). By adjusting this geometric parameter, the patent achieves transverse mode suppression while preventing the formation of slanted stopbands that would degrade filter performance.
2Reliability
If the IDT electrode thickness is increased to improve coupling coefficient, then electromechanical coupling is enhanced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by specifying an optimized thickness range for the IDT electrode (0.06λ to 0.10λ, preferably 0.07λ to 0.09λ). This parameter optimization enhances the electromechanical coupling coefficient while avoiding excessive thickness that would complicate device structure and manufacturing.
Solution Approach 2:
The patent uses partial action by applying a moderate tilt angle (0° to 10°) rather than a large angle. This partial application of tilting provides sufficient transverse mode suppression while avoiding the complexities and manufacturing difficulties associated with highly tilted structures.
3Reliability
If pitch modulation is applied to shift stopband, then stopband position is adjusted outside frequency range of interest, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing pitch modulation only in specific regions of the IDT electrode rather than uniformly across the entire structure. This localized approach shifts the stopband to the desired position while minimizing the increase in device complexity.
Solution Approach 2:
The patent uses segmentation by dividing the IDT electrode into multiple sections with different pitch values. This segmentation allows precise control over stopband positioning while maintaining a manageable device structure that is easier to manufacture compared to uniform pitch designs.
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 enhances the frequency response of acoustic wave filters by reducing unwanted noise and improving filter characteristics, including suppression of transverse mode spurious responses and slanted stopbands.
Implementation Method 1
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer on which the interdigital transductor electrode is disposed.
Data Source
AI summary
Acoustic wave device is disclosed. the acoustic wave device can include a piezoelectric layer and an interdigital transducer electrode over the piezoelectric layer. The interdigital transducer electrode having a non-zero tilt angle. The non-zero tilt angle can between 5° to 15°. The interdigital transducer electrode is configured to shift stopband of the acoustic wave device and to reduce a slanted stopband.