Elastic Wave Filter Electrode Layout for Surge Voltage Resistance

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Solution Overview

Problem

Elastic wave elements in mobile communication devices are vulnerable to surge voltages, leading to potential deformation or destruction of electrode fingers due to instantaneous potential differences between IDT electrodes and reflectors, especially at higher frequencies, necessitating improved voltage resistance.

Innovation Solution

The elastic wave element incorporates a piezoelectric substrate with an IDT electrode and a reflector, featuring comb-shaped electrodes and a connecting electrode that electrically couples reflective and first electrode fingers, reducing discharge occurrences and enhancing voltage resistance by maintaining equal potentials between adjacent electrode fingers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the IDT electrode is connected to the reflectors using the busbar electrodes, then the elastic wave element has a certain degree of voltage resistance, but when a surge voltage is applied, the electrode fingers may be deformed or destroyed due to an instantaneous potential difference occurring between the IDT electrode and the reflector

Engineering Contradiction:

Improvevoltage resistanceVSAvoidelectrode finger deformation or destruction

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent connects the busbar electrode of the IDT electrode to the busbar electrode of the reflector, creating an equipotential structure that eliminates instantaneous potential differences between adjacent electrode fingers. This prevents discharge and protects electrode fingers from deformation or destruction during surge voltage events.

Inventive Principle:

Principle #12Equipotentiality

Solution Approach 2:

The busbar electrode acts as an intermediary conductor that equalizes potential between the IDT electrode and the reflector. By providing a low-impedance connection path, it prevents direct discharge between adjacent electrode fingers during surge voltage events.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the frequency is increased, then the performance of the elastic wave element is improved, but the distance between the IDT electrode and the reflectors becomes smaller, increasing the vulnerability to surge voltage

Engineering Contradiction:

ImprovefrequencyVSAvoidvoltage resistance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent implements an equipotential connection between the IDT electrode and reflector through busbar electrodes. This ensures that even as the distance between components decreases with increased frequency, the potential difference remains zero, preventing discharge and maintaining voltage resistance at higher frequencies.

Inventive Principle:

Principle #12Equipotentiality

3Object-affected harmful factors

If a surge voltage is applied to the elastic wave element, then discharge occurs between adjacent electrode fingers, but the busbar electrode connection prevents this discharge by maintaining equal potentials

Engineering Contradiction:

Improvedischarge between electrode fingersVSAvoidelectrode connection structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses busbar electrodes to create equipotential regions that connect the IDT electrode and reflector. This simple yet effective approach prevents discharge between adjacent electrode fingers without requiring complex protection circuits or additional components.

Inventive Principle:

Principle #12Equipotentiality

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 effectively reduces or prevents discharge between adjacent electrode fingers, thereby improving the voltage resistance of the elastic wave element and filter device, even under instantaneous high voltage conditions.

Implementation Method 1

an elastic wave element according to a preferred embodiment of the present invention includes a piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an IDT electrode and a reflector. The IDT electrode is provided on the piezoelectric substrate

Methodology Applied

Scientific EffectSurface acoustic wave generation: Surface Acoustic Wave

Data Source

PatentUS10476473B2Elastic wave element and elastic wave filter device

Publication Date: 2019.11.12 MURATA MFG CO LTD

AI summary

An elastic wave element includes a piezoelectric substrate, an IDT electrode including a first comb-shaped electrode and a second comb-shaped electrode, and reflectors. Each of the reflectors includes a first reflective busbar electrode, a second reflective busbar electrode, and reflective electrode fingers. The first comb-shaped electrode includes a first busbar electrode connected to the first reflective busbar electrodes, and first electrode fingers. The second comb-shaped electrode includes a second busbar electrode and second electrode fingers. In in-between areas, in each of which a reflective electrode finger and a first electrode finger adjacent to each other in the elastic-wave propagation direction face each other, connecting electrodes which electrically couple the reflective electrode fingers to the first electrode fingers are provided.