IDT Electrode Finger Structure for Transverse Mode Ripple Suppression

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Solution Overview

Problem

Existing elastic wave devices face limitations in effectively suppressing transverse mode ripples due to constraints on increasing the width of elongated sections in electrode fingers, which also complicate the manufacturing process and increase costs.

Innovation Solution

The design includes a piezoelectric substrate with an interdigital transducer (IDT) electrode featuring elongated sections in both electrode fingers and busbars, along with strategically placed openings in the busbar sections to create regions of varying acoustic velocities, allowing for a piston mode that reduces transverse mode ripples without the need for additional films.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the width of the elongated sections is excessively increased, then the low acoustic velocity region is formed, but the elongated sections may contact adjacent electrode fingers

Engineering Contradiction:

Improvetransverse mode ripple suppressionVSAvoidelectrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The busbar is divided into multiple segments with openings between them, creating a segmented structure that forms the low acoustic velocity region without requiring excessively wide elongated sections. This segmentation allows the electrode fingers to remain separated while still achieving the desired acoustic velocity distribution for transverse mode ripple suppression.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a film is disposed on part of an IDT electrode to form a low acoustic velocity region, then transverse mode ripples are suppressed, but the manufacturing process complexity and cost increase

Engineering Contradiction:

Improvetransverse mode ripple suppressionVSAvoidmanufacturing process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts the low acoustic velocity region formation from the film deposition process and achieves it through the geometric configuration of the busbar and electrode fingers themselves. By removing the need for additional film layers and focusing on the structural arrangement, the manufacturing process is simplified while maintaining the transverse mode ripple suppression effect.

Inventive Principle:

Principle #2Taking out (Extraction)

3Speed

If the width of the elongated sections is excessively increased, then the low acoustic velocity region is formed, but the acoustic velocity is not sufficiently decreased due to contact with adjacent electrode fingers

Engineering Contradiction:

Improveacoustic velocity in low acoustic velocity regionVSAvoidtransverse mode ripple suppression

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The busbar is segmented with openings that prevent contact between elongated sections and adjacent electrode fingers, allowing the low acoustic velocity region to achieve sufficiently low acoustic velocity without the harmful contact effect. This segmentation enables proper acoustic velocity distribution for effective transverse mode ripple suppression.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The openings in the busbar create localized regions with different acoustic properties. The segmented structure provides local quality variations that ensure the low acoustic velocity region maintains its intended acoustic velocity characteristics without being compromised by contact with adjacent electrode fingers.

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

This configuration significantly reduces or prevents transverse mode ripples while maintaining manufacturing simplicity and cost-effectiveness by creating a piston mode through controlled acoustic velocity regions, effectively trapping elastic waves and minimizing leakage.

Implementation Method 1

a piezoelectric substrate and an IDT electrode disposed on the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a low acoustic velocity region is formed... the acoustic velocity of a low acoustic velocity region is reduced

Methodology Applied

Scientific EffectAcoustic wave propagation: Surface Acoustic Wave

Data Source

PatentUS10009009B2Elastic wave device including electrode fingers with elongated sections

Publication Date: 2018.06.26 MURATA MFG CO LTD

AI summary

In an elastic wave device, an interdigital transducer (IDT) electrode is disposed on a piezoelectric substrate. In at least one of first and second electrode fingers of the IDT electrode, elongated sections with a widthwise dimension larger than that of a center of the first and second electrode fingers in a longitudinal direction are provided in at least one of a portion closer to a base end of the first or second electrode finger and a portion closer to a leading end of the first or second electrode finger than a central region of the first or second electrode finger. At least one of first and second busbars includes a plurality of openings provided separately from each other along the longitudinal direction of the first and second busbars.