Plate Wave Element Structure for Temperature-Stable Lamb Waves

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Solution Overview

Problem

Conventional plate wave elements suffer from poor frequency temperature characteristics and structural weakness due to the thinness required for high-speed wave excitation, leading to potential cracking under stress.

Innovation Solution

Incorporating a medium layer with a frequency temperature coefficient opposite to that of the piezoelectric body, sandwiched between the piezoelectric body and the comb-shaped electrode, to enhance the frequency temperature characteristic and structural strength, while using a support substrate to increase the element's durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the piezoelectric body is made extremely thin to excite high-speed plate waves, then the wave propagation speed is improved, but the structural strength deteriorates leading to potential cracking

Engineering Contradiction:

Improvewave propagation speedVSAvoidstructural strength

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The patent applies composite material structure by combining the piezoelectric body with medium layers having different acoustic impedance. This composite structure allows the piezoelectric body to maintain its thinness for high-speed wave propagation while the overall structure gains enhanced strength and stability through the supporting medium layers.

Inventive Principle:

Principle #40Composite materials

2Productivity

If the piezoelectric body is made extremely thin to excite plate waves, then the wave excitation capability is improved, but the frequency temperature characteristic deteriorates

Engineering Contradiction:

Improvewave excitation capabilityVSAvoidfrequency temperature characteristic

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the physical parameters of the surrounding medium by introducing medium layers with specific acoustic impedance and temperature characteristics. This parameter modification allows the thin piezoelectric body to maintain both its wave excitation capability and improved frequency temperature characteristic through the compensating effect of the medium layers.

Inventive Principle:

Principle #35Parameter changes

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 solution significantly improves the frequency temperature characteristic and structural integrity of the plate wave element, allowing for more reliable operation across temperature variations without compromising the electromechanical coupling coefficient.

Implementation Method 1

Comb-shaped electrode 104 excites a plate wave

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The medium layer has a frequency temperature characteristic opposite to that of the piezoelectric body

Methodology Applied

Scientific EffectFrequency temperature characteristic compensation:

Data Source

PatentUS8482184B2Plate wave element and electronic equipment using same

Publication Date: 2013.07.09 SKYWORKS PANASONIC FILTER SOLUTIONS JAPAN

AI summary

A plate wave element includes a piezoelectric body, a comb-shaped electrode disposed on an upper surface of the piezoelectric body, and a medium layer disposed on the upper surface of the piezoelectric body so as to cover the comb-shaped electrode. The comb-shaped electrode excites a Lamb wave as a main wave. The medium layer has a frequency temperature characteristic opposite to that of the piezoelectric body. The plate wave element has a preferable frequency temperature characteristic.