Rounded IDT Electrode Structure for Transverse Mode Suppression
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Solution Overview
Problem
Surface acoustic wave filters face performance degradation due to transverse leakage, which affects the accuracy and stability of oscillators and sensors, and introduces passband ripples and limited rejection in radio frequency applications.
Innovation Solution
The implementation of a partially rounded interdigital transducer electrode with a corner radius in the range of 0.01 to 0.1 times the wavelength, which suppresses transverse modes without additional structural elements like silicon nitride layers or mass loading strips, by selectively rounding the corners of the interdigital transducer electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional interdigital transducer electrodes with sharp corners are used, then the device structure is simple and easy to manufacture, but transverse modes are not suppressed leading to performance degradation
Solution Approach 1:
The patent applies local quality by rounding only the corners of the interdigital transducer electrode fingers while maintaining the straight edges and overall geometry. This localized modification at the corner regions suppresses transverse modes and eliminates passband ripples without requiring changes to the entire electrode structure, thus improving filter performance while keeping the overall design simple.
Solution Approach 2:
The patent implements curvature by replacing the sharp 90-degree corners of the electrode fingers with rounded corners having a specific radius (typically 0.01 to 0.05 times the finger width). This curvature modification changes the acoustic wave generation characteristics at the corners, suppressing transverse modes and improving filter rejection without adding structural complexity.
2Reliability
If additional structural elements like silicon nitride layers or mass loading strips are added to suppress transverse modes, then transverse mode suppression is achieved, but the device structure complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for additional structural elements such as silicon nitride layers, mass loading strips, or aperture gratings that are commonly used for transverse mode suppression. Instead, it achieves the same function through a simple geometric modification of the existing interdigital transducer electrode corners, thereby suppressing transverse modes without increasing structural complexity.
Solution Approach 2:
The patent changes the geometric parameter of the electrode corners from sharp (zero radius) to rounded (finite radius). This parameter change in the electrode geometry alone is sufficient to suppress transverse modes and improve filter performance, eliminating the need for additional structural elements and keeping the device simple.
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 suppresses transverse modes, maintaining the electromechanical coupling coefficient and quality factor, while reducing the complexity of the acoustic wave device structure and improving the filter's performance by minimizing passband ripples and enhancing rejection.
Implementation Method 1
a piezoelectric layer; and an interdigital transducer electrode formed with the piezoelectric layer
Data Source
AI summary
An acoustic wave device is disclosed. The acoustic wave device can include a piezoelectric layer, and an interdigital transducer electrode formed with the piezoelectric layer. The interdigital transducer electrode includes a finger extending from a bus bar. The finger has a first region and a second region between the first region and the bus bar. The finger has a lower side and an upper side opposite the lower side. The lower side is closer to the piezoelectric layer than the upper side. Widths of the lower side in the first and second regions are generally the same, and a width of the upper side in the first region is greater than a width of the upper side in the second region.