SAW Resonator Border Electrode Structure for Transverse Mode Suppression

Solution Overview

Problem

Existing acoustic wave filters, particularly surface acoustic wave (SAW) devices, suffer from strong transverse modes that hinder accuracy and stability of oscillators and sensors, and degrade filter performance by causing passband ripples and limited rejection.

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 factors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional SAW device structures are used, then device simplicity is maintained, but transverse modes are strong causing passband ripples and limited rejection

Engineering Contradiction:

Improvefilter performanceVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The device is segmented into distinct regions: a central active region and a border region with different acoustic velocity. This segmentation allows the border region to suppress transverse modes while the active region maintains signal generation, resolving the contradiction between filter performance and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are given different acoustic velocity properties. The border region has a first acoustic velocity while the active region has a second acoustic velocity, creating local quality differences that suppress transverse modes without affecting the overall device function.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If border region with different velocity is implemented, then transverse modes are suppressed improving accuracy and stability, but device structure becomes more complex

Engineering Contradiction:

Improveoscillator accuracyVSAvoidstructure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The device is segmented into distinct regions: a central active region and a border region with different acoustic velocity. This segmentation allows the border region to suppress transverse modes while the active region maintains signal generation, resolving the contradiction between filter performance and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are given different acoustic velocity properties. The border region has a first acoustic velocity while the active region has a second acoustic velocity, creating local quality differences that suppress transverse modes without affecting the overall device function.

Inventive Principle:

Principle #3Local quality

3Reliability

If border region with different velocity is implemented, then passband ripples are reduced improving filter performance, but device structure becomes more complex

Engineering Contradiction:

Improvefilter performanceVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The device is segmented into distinct regions: a central active region and a border region with different acoustic velocity. This segmentation allows the border region to suppress transverse modes while the active region maintains signal generation, resolving the contradiction between filter performance and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are given different acoustic velocity properties. The border region has a first acoustic velocity while the active region has a second acoustic velocity, creating local quality differences that suppress transverse modes without affecting the overall device function.

Inventive Principle:

Principle #3Local quality

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 k2 and Q factors.

Implementation Method 1

a piezoelectric layer over the support substrate; and an interdigital transducer electrode in electrical communication with the piezoelectric layer, the surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20250330139A1Piston mode for surface acoustic wave device

Publication Date: 2025.10.23 SKYWORKS SOLUTIONS INC

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 thickness, a second portion with a second thickness between the center region and the first portion, and a third portion with a third thickness between the center region and the second portion. The finger in the center region has a fourth thickness. The first thickness and the third thickness are thicker than the second thickness and the fourth thickness.