Surface Acoustic Wave Filter Layout for Higher Power Handling

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Solution Overview

Problem

Surface acoustic wave filters face a trade-off between improving electric power handling capability and downsizing, as increasing power handling leads to mechanical and electrical stresses and potential damage to IDT electrodes, and series division of resonators results in increased electrode area and capacitance requirements.

Innovation Solution

A surface acoustic wave device with parallel-connected resonator groups, where one group has a higher resonant frequency and fewer series divisions than the other, maintaining combined capacitance while reducing the area on the piezoelectric substrate, and incorporating reflectors to manage power distribution efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If series division of resonators is implemented to improve electric power handling capability, then power handling capability is improved, but electrode area increases proportionally to the square of the number of division stages

Engineering Contradiction:

Improveelectric power handling capabilityVSAvoidelectrode area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The resonator is divided into multiple stages connected in series, with each stage having a portion of the total capacitance. This segmentation distributes the electrical stress and power handling requirements across multiple smaller units, improving overall power handling capability while controlling the total electrode area through optimized capacitance distribution.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention optimizes the capacitance values of individual IDT electrodes in each series stage to achieve the desired total capacitance while minimizing the total electrode area. By carefully selecting and adjusting capacitance parameters of each stage, the design balances power handling requirements with area constraints.

Inventive Principle:

Principle #35Parameter changes

2Power

If high power is applied to achieve high output, then output power is improved, but electrical and mechanical stresses and piezoelectric effects cause characteristic deterioration and electrode damage

Engineering Contradiction:

Improveoutput powerVSAvoidresonator characteristic stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The series connection of multiple resonator stages with optimized capacitance values acts as a cushioning mechanism that distributes and absorbs electrical and mechanical stresses before they can concentrate and cause damage to individual electrodes, thereby preventing characteristic deterioration and electrode failure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 enhances electric power handling capability while minimizing the increase in resonator size and maintaining impedance, reducing power consumption and electrode area, thus balancing filter size and performance.

Implementation Method 1

a piezoelectric substrate, at least a first resonator group, and at least a second resonator group which are connected in parallel to each other and are defined by surface acoustic wave resonators each including an IDT electrode provided on the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11601114B2Surface acoustic wave device and surface acoustic wave filter

Publication Date: 2023.03.07 MURATA MFG CO LTD

AI summary

A surface acoustic wave filter includes series and parallel arm resonance sections. The series arm resonance section is in a series arm. The parallel arm resonance section is in a parallel arm. The series arm resonance section includes one or more surface acoustic wave devices. Each surface acoustic wave device includes a first resonator group and a second resonator group. The first and second resonator groups are connected in parallel and include surface acoustic wave resonators. The first resonator group includes at least one surface acoustic wave resonator. The second resonator group includes a greater number of surface acoustic wave resonators than the at least one surface acoustic wave resonator in the first resonator group. The resonant frequency of the surface acoustic wave resonator in the first resonator group is higher than the resonant frequency of the surface acoustic wave resonators in the second resonator group.