IDT Electrode Cavity Layout for Low-Spurious Acoustic Wave Elements
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Solution Overview
Problem
Existing acoustic wave elements, particularly those with piezoelectric layers and IDT electrodes, face challenges in optimizing frequency characteristics and reducing spurious components due to the design of the electrode fingers and busbars, which affect the efficiency of signal conversion.
Innovation Solution
The acoustic wave element incorporates a design with alternating electrode fingers of varying widths, specifically a wider portion on the base side of the electrode fingers, and a cavity formed between the piezoelectric layer and the support, enhancing the frequency characteristics and reducing spurious components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the IDT electrode uses uniform electrode fingers and busbars, then the structure is simple and easy to manufacture, but the frequency characteristics are poor and spurious components increase
Solution Approach 1:
The patent applies local quality by making the electrode fingers have different widths at different positions. Specifically, the electrode fingers have a wider portion at the base side and a narrower portion at the tip side, creating non-uniform mass distribution along the electrode length. This local variation in geometry optimizes the frequency characteristics and reduces spurious components while maintaining overall structural simplicity
Solution Approach 2:
The patent changes the geometric parameters of the electrode fingers by varying the width along their length. The width parameter transitions from a wider base portion to a narrower tip portion, creating a gradual parameter change that improves frequency response. This parameter variation allows optimization of electrical and mechanical properties without fundamentally changing the electrode structure
2Manufacturing precision
If the cavity is positioned to overlap the central region of the IDT electrode, then frequency characteristics improve, but the electrode mass distribution becomes unbalanced
Solution Approach 1:
The patent compensates for the unbalanced mass distribution caused by cavity positioning by creating local mass variations in the electrode fingers. The wider base portion and narrower tip portion are strategically designed to balance the overall mass distribution, offsetting the asymmetry introduced by the cavity's position over the central region
Solution Approach 2:
The patent introduces asymmetry in the electrode finger geometry (wider base, narrower tip) to counterbalance the asymmetric mass distribution created by the cavity positioning. This controlled asymmetry in electrode design compensates for the asymmetric support structure, maintaining overall system balance while allowing the cavity to be positioned for optimal frequency characteristics
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 design improves frequency characteristics and reduces spurious components, enabling higher frequency operation and more efficient signal conversion, particularly in resonators and filters.
Implementation Method 1
a piezoelectric layer on the support... capable of performing at least one of conversion from an acoustic wave to an electric signal or conversion from an electric signal to an acoustic wave
Data Source
AI summary
A cavity overlapping an IDT electrode in a see-through plan view is formed between a piezoelectric layer and a support. An intersection region where first electrode fingers and second electrode fingers overlap includes a central region and two end regions located on both sides of the central region in one-to-one correspondence. The cavity overlaps the central region. An edge of the cavity on a side closer to the first busbar is located within a range from an edge of the central region on a side closer to the first busbar to an edge of the first busbar on a side opposite to the central region. The first electrode fingers extending from the first busbar each include a first portion located in the central region and a second portion located on a side closer to the first busbar or a side closer to the second busbar relative to the central region.