Layered Acoustic Wave Structure for Higher-Order Mode Suppression
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Solution Overview
Problem
Existing acoustic wave devices face challenges in reducing higher-order modes, particularly in the 5-GHz band, which can interfere with filter characteristics when connected to common elements like antennas.
Innovation Solution
The acoustic wave device incorporates a structure with a support substrate, a first high acoustic velocity film, a low acoustic velocity film, a second high acoustic velocity film, and a piezoelectric layer, where the second high acoustic velocity film is faster than the first, effectively confining the higher-order modes and reducing their propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional acoustic wave device structure is used, then the device can operate in the 5-GHz band, but higher-order modes occur and interfere with filter characteristics
Solution Approach 1:
The device is divided into multiple functional layers with distinct acoustic velocity characteristics: a support substrate, a first high acoustic velocity film, a low acoustic velocity film, and a second high acoustic velocity film. This segmentation creates a layered structure where each layer contributes to controlling acoustic wave propagation and suppressing higher-order modes
Solution Approach 2:
Different regions of the device have locally optimized acoustic velocity properties. The first and second high acoustic velocity films are positioned at specific locations to create acoustic impedance variations that confine higher-order modes, while the low acoustic velocity film provides contrast to enhance the confinement effect
2Speed
If the acoustic velocity in all films is increased to improve main mode performance, then the main mode intensity improves, but higher-order modes become more pronounced
Solution Approach 1:
The acoustic velocity parameter is varied across different layers rather than being uniformly high. The first high acoustic velocity film has a velocity faster than the piezoelectric layer, the low acoustic velocity film has a velocity slower than the piezoelectric layer, and the second high acoustic velocity film has a velocity faster than or equal to the first high acoustic velocity film. This parameter variation creates acoustic confinement
Solution Approach 2:
The device uses a composite structure combining materials with different acoustic velocity characteristics. The support substrate, high acoustic velocity films, low acoustic velocity film, and piezoelectric layer are composed of different materials selected to provide the required acoustic velocity profile for mode confinement
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 significantly reduces higher-order modes, minimizing interference with filter characteristics in the 5-GHz band and maintaining main mode intensity, ensuring effective performance when connected to common elements.
Implementation Method 1
a bulk wave propagates in the low acoustic velocity film more slowly than a bulk wave propagates in the piezoelectric layer, a bulk wave propagates in the first high acoustic velocity film faster than an acoustic wave propagates on the piezoelectric layer, and a bulk wave propagates in the second high acoustic velocity film faster than or as fast as a bulk wave propagates in the first high acoustic velocity film
Implementation Method 2
a piezoelectric layer on the second high acoustic velocity film
Data Source
AI summary
An acoustic wave device includes a support substrate, a first high acoustic velocity film on the support substrate, a low acoustic velocity film on the first high acoustic velocity film, a second high acoustic velocity film on the low acoustic velocity film, a piezoelectric layer on the second high acoustic velocity film, and an IDT on the piezoelectric layer. Bulk waves propagate in the low acoustic velocity film more slowly than bulk waves propagate in the piezoelectric layer, bulk waves propagate in the first high acoustic velocity film faster than acoustic waves propagate on the piezoelectric layer, and bulk waves propagate in the second high acoustic velocity film faster than or as fast as bulk waves propagate in the first high acoustic velocity film.