Split Ladder Acoustic Wave Filters With Dual Material Stacks

Solution Overview

Problem

Conventional RF filters using acoustic wave resonators face challenges in achieving optimal performance due to the need for a single material stack that meets the different requirements of series and shunt resonators, leading to suboptimal design trade-offs in insertion loss, temperature stability, and power handling.

Innovation Solution

The implementation of a split ladder filter design, where series and shunt resonators are fabricated on separate chips with distinct material stacks, allowing for independent optimization of each resonator type to improve performance and reduce spurious modes, thereby enhancing temperature stability and insertion loss characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single material stack is used for both series and shunt resonators, then manufacturing complexity is reduced, but performance optimization is compromised due to conflicting requirements

Engineering Contradiction:

Improvemanufacturing complexityVSAvoidperformance optimization

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The filter is divided into two separate chips: a first chip containing series resonators and a second chip containing shunt resonators. This segmentation allows each chip to have its own optimized material stack, resolving the conflict between manufacturing simplicity and performance optimization by trading increased device complexity for superior resonator performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different material stacks are applied to different parts of the system - the first chip has a material stack optimized for series resonators while the second chip has a material stack optimized for shunt resonators. This local quality approach allows each resonator type to operate at its optimal performance point without compromise.

Inventive Principle:

Principle #3Local quality

2Reliability

If separate chips with distinct material stacks are used for series and shunt resonators, then performance and temperature stability are improved, but device complexity increases

Engineering Contradiction:

Improvetemperature stabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The filter is divided into two separate chips: a first chip containing series resonators and a second chip containing shunt resonators. This segmentation allows each chip to have its own optimized material stack, resolving the conflict between manufacturing simplicity and performance optimization by trading increased device complexity for superior resonator performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The material composition and structure parameters are changed between the two chips to optimize for different resonator types. The first chip uses a material stack with parameters optimized for series resonators while the second chip uses different parameters optimized for shunt resonators, achieving superior temperature stability and performance.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single material stack is used, then device complexity is reduced, but insertion loss and spurious modes cannot be optimized

Engineering Contradiction:

Improvedevice complexityVSAvoidinsertion loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The filter is divided into two separate chips: a first chip containing series resonators and a second chip containing shunt resonators. This segmentation allows each chip to have its own optimized material stack, resolving the conflict between manufacturing simplicity and performance optimization by trading increased device complexity for superior resonator performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different material stacks are applied to different parts of the system - the first chip has a material stack optimized for series resonators while the second chip has a material stack optimized for shunt resonators. This local quality approach allows each resonator type to operate at its optimal performance point without compromise.

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 approach enables improved temperature stability and reduced insertion loss across a wide range of frequencies, meeting specific requirements for RF filters in communications devices, such as LTE Band 2 transmit filters, while maintaining lower cost and power efficiency.

Implementation Method 1

a first piezoelectric material layer, a second piezoelectric material layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

acoustic wave resonators, series and shunt resonators are fabricated on separate chips

Methodology Applied

Scientific EffectAcoustic wave resonance: Resonance

Data Source

PatentUS10917072B2Split ladder acoustic wave filters

Publication Date: 2021.02.09 MURATA MFG CO LTD

AI summary

Filter devices and methods of fabricating filter devices. A filter device includes a first chip and a second chip. The first chip has a first material stack and contains one or more series resonators of a ladder filter circuit. The second chip has a second material stack and contains one or more shunt resonators of the ladder filter circuit. The first material stack and the second material stack are different.