SAW Electrode Border Structure for Transverse Mode Suppression
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Solution Overview
Problem
Existing surface acoustic wave (SAW) devices face challenges with strong transverse modes that hinder accuracy and stability of oscillators and filters by causing passband ripples and limited rejection, despite having high quality factor (Q) and effective electromechanical coupling coefficient (k2eff).
Innovation Solution
Implementing a multilayer piezoelectric substrate SAW device with a border region having a different velocity from the central active region, featuring structures like multi-hammer head, notch, trench, or multi-thickness steps to suppress transverse modes without significantly degrading k2 or Q.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SAW device structures are used, then high quality factor (Q) and effective electromechanical coupling coefficient (k2eff) are achieved, but strong transverse modes cause passband ripples and limited rejection
Solution Approach 1:
The device is divided into a central active region and a border region with different acoustic velocities. This segmentation allows the border region to suppress transverse modes while the central region maintains high Q and k2eff, resolving the contradiction between reliability and harmful transverse modes.
Solution Approach 2:
Different regions of the device are given different acoustic velocity characteristics. The central active region maintains standard properties for high performance, while the border region has modified acoustic velocity specifically for transverse mode suppression, applying local quality to solve the contradiction.
2Reliability
If border region structures are added to suppress transverse modes, then accuracy and stability improve, but device complexity increases
Solution Approach 1:
The solution adds a spatial dimension by introducing a border region surrounding the central active region. This dimensional expansion allows transverse mode suppression without complicating the fundamental central structure, maintaining manufacturing simplicity while improving reliability.
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 proposed structures effectively suppress transverse modes, enhancing the accuracy and stability of SAW devices by reducing passband ripples and improving rejection, while maintaining high performance in filters and oscillators.
Implementation Method 1
a piezoelectric layer over the support substrate; and an interdigital transducer electrode in electrical communication with the piezoelectric layer, the interdigital transducer electrode including a bus bar and a finger extending from the bus bar
Data Source
AI summary
A multilayer piezoelectric substrate acoustic wave device including an active region having a center region and a border region is disclosed. The acoustic wave device can include a support substrate, a piezoelectric layer over the support substrate, and an interdigital transducer electrode in electrical communication with the piezoelectric layer. The interdigital transducer electrode includes a bus bar and a finger extending from the bus bar. The finger in the border region has a first portion with a first width, a second portion with a second width between the center region and the first portion, and a third portion with a third width between the center region and the second portion. The finger in the center region has a fourth width. The first width and the third width are wider than the second width and the fourth width.