Acoustic Wave Device Slow Wave Overlay Width Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional acoustic wave devices, such as SAW resonators, are limited by the velocity of acoustic waves in piezoelectric layers, restricting their utility to processing high-frequency signals and suffer from spurious responses and temperature dependence, which hinders their application in multi-frequency devices.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with a slow wave propagation overlay, where the width of the overlay varies based on the distance between adjacent electrode fingers, allowing adjustment of wave propagation velocity to maintain a desirable piston mode and reduce transverse and Love mode content, thereby enhancing frequency range and reducing spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional SAW resonator structure is used, then the device can process high-frequency signals, but the acoustic wave velocity is limited and spurious responses occur
Solution Approach 1:
The patent applies local quality by creating regions with different overlay widths beneath the electrode fingers. Specifically, a first region has a first overlay width while a second region has a second overlay width that is different from the first. This spatial variation in overlay dimensions allows different local areas to support different wave modes, enabling the device to achieve higher acoustic wave velocities in certain regions while maintaining piston mode dominance and reducing spurious responses through the controlled variation of wave propagation characteristics across the device structure.
2Measurement precision
If the electrode period and metallization ratio are optimized for high frequency, then the series resonant frequency increases, but temperature dependence and spurious responses increase
Solution Approach 1:
The patent employs parameter changes by systematically varying the overlay width parameter across different regions of the device. The first overlay width and second overlay width are specifically designed to different values, creating a gradient or stepped variation in the wave propagation medium. This parameter variation allows the device to maintain accurate frequency response characteristics while compensating for temperature effects and suppressing spurious responses, as the different overlay widths create complementary frequency responses that can be optimized for stability across operating conditions.
3Device complexity
If a uniform overlay width is used beneath all electrode fingers, then the device structure is simple, but the wave propagation velocity cannot be optimized for piston mode
Solution Approach 1:
The patent implements local quality by designing the overlay structure with spatially varying widths rather than a uniform configuration. The first region beneath certain electrode fingers has a first overlay width optimized for specific wave propagation characteristics, while the second region beneath other electrode fingers has a second overlay width optimized for different characteristics. This localized optimization enables the device to achieve enhanced wave propagation velocity and improved piston mode performance without requiring complete structural redesign, as only specific regions are modified while maintaining overall structural coherence.
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 enables improved frequency range and reduced spurious responses, allowing for more effective processing of high-frequency signals while maintaining the desired piston mode, thus overcoming the limitations of conventional devices.
Implementation Method 1
Acoustic wave devices include a piezoelectric material in contact with one or more electrodes. Piezoelectric materials acquire a charge when compressed, twisted, or distorted, and similarly compress, twist, or distort when a charge is applied to them.
Implementation Method 2
a slow wave propagation overlay over at least a portion of the first set of electrode fingers and the second set of electrode fingers such that a width of the slow wave propagation overlay measured along the lateral axis varies based on the distance between adjacent electrode fingers
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer, an interdigital transducer, and a slow wave propagation overlay over a portion of the interdigital transducer. By providing electrode fingers of the interdigital transducer such that a portion of the width thereof is dependent on an electrode period, a desirable wave mode may be maintained in the acoustic wave device. Further, by varying a width of the slow wave propagation overlay based on the electrode period, the desirable wave mode may be further maintained.