BAW and Multilayer SAW Multiplexer Layout for Low Insertion Loss

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Solution Overview

Problem

Designing multiplexers with acoustic wave filters to meet performance specifications with low loss is challenging due to loading issues, especially in complex radio frequency systems where multiple filters are coupled together, leading to increased insertion loss and degradation of transmission characteristics.

Innovation Solution

The implementation of a multiplexer that includes a bulk acoustic wave (BAW) filter with a lower pass band and a multilayer piezoelectric substrate surface acoustic wave (SAW) filter with a higher pass band, where the BAW filter achieves desirable gamma for higher frequencies and the SAW filter achieves desirable gamma for lower frequencies, reducing loading and insertion loss by setting the pass bands appropriately.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple acoustic wave filters are coupled together in a multiplexer, then the multiplexer can support multiple frequency bands and carrier aggregation, but the insertion loss increases and transmission characteristics degrade due to loading effects

Engineering Contradiction:

Improvefrequency band supportVSAvoidinsertion loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The multiplexer is segmented into distinct filter sections, each handling specific frequency bands. The first acoustic wave filter handles lower frequency bands while the second acoustic wave filter handles higher frequency bands, with each filter optimized for its designated range to minimize loading effects on the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different acoustic wave filter types are used for different frequency bands within the multiplexer. Bulk acoustic wave resonators are employed in the first filter for lower frequencies where they provide desirable gamma, while multilayer piezoelectric substrate surface acoustic wave resonators are used in the second filter for higher frequencies where they achieve better gamma performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If bulk acoustic wave resonators are used for lower frequency bands, then desirable gamma is achieved for higher frequencies, but spurious modes appear below the pass band

Engineering Contradiction:

Improvegamma performanceVSAvoidspurious modes

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The harmful spurious modes generated by bulk acoustic wave resonators are extracted and isolated from the signal path by positioning them below the pass band. The filter design ensures that spurious modes fall outside the operational frequency ranges of both pass bands, preventing interference with transmitted signals.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The spurious modes of the bulk acoustic wave resonators, which would normally be harmful, are strategically positioned below the first pass band and outside the second pass band. This converts the potential harm into a beneficial arrangement where the spurious modes do not interfere with either frequency band operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If multilayer piezoelectric substrate surface acoustic wave resonators are used for higher frequency bands, then desirable gamma is achieved for lower frequencies, but the pass band must be positioned above the first pass band

Engineering Contradiction:

Improvegamma performanceVSAvoidfilter arrangement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The frequency arrangement transitions from a single-dimensional sequential layout to a two-dimensional frequency space utilization. The first pass band and second pass band are positioned at different frequency levels, with the second pass band above the first, allowing each filter type to operate in its optimal frequency range while sharing a common node.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 results in low loading loss and low insertion loss for the multiplexer, supporting carrier aggregation of multiple frequency bands with improved transmission characteristics and reduced degradation, making it suitable for complex RF systems.

Implementation Method 1

The first acoustic wave filter includes bulk acoustic wave resonators

Methodology Applied

Scientific EffectBulk acoustic wave: Acoustics

Implementation Method 2

The second acoustic wave filter includes multilayer piezoelectric substrate surface acoustic wave resonators

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Implementation Method 3

multilayer piezoelectric substrate surface acoustic wave resonators

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11658688B2Multiplexer with bulk acoustic wave filter and multilayer piezoelectric substrate filter

Publication Date: 2023.05.23 SKYWORKS SOLUTIONS INC

AI summary

Embodiments of this disclosure relate to multiplexers that include acoustic wave filters for filtering radio frequency signals. In certain embodiments, a multiplexer includes a first acoustic wave filter including bulk acoustic wave resonators and a second acoustic wave filter including multilayer piezoelectric substrate surface acoustic wave resonators. The second acoustic wave filter can have a second pass band that is above a first pass band of the first acoustic wave filter. Related acoustic filter assemblies, packaged radio frequency modules, wireless communication devices, and methods are disclosed.