Parallel SAW Filter Circuit for Bulk Mode Suppression

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Solution Overview

Problem

Existing acoustic wave filters, particularly surface acoustic wave (SAW) filters, suffer from bulk mode responses that degrade insertion loss performance and signal leakage, especially in multiplexers, which are challenging to suppress using conventional methods.

Innovation Solution

Incorporating an acoustic wave resonator in parallel with a circuit element, such as a capacitor or another resonator, with different resonant frequencies, to suppress bulk mode frequencies and improve insertion loss performance, particularly in surface acoustic wave filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If surface acoustic wave filters are used, then chip size and cost are reduced, but bulk mode responses degrade insertion loss performance and cause signal leakage

Engineering Contradiction:

Improvechip sizeVSAvoidinsertion loss performance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent converts the harmful bulk mode responses into beneficial effects by placing resonators at specific locations and orientations within the SAW filter structure. These resonators are designed to have resonant frequencies that coincide with the bulk mode frequencies, transforming the harmful bulk wave propagation into useful signal paths that improve insertion loss performance while maintaining the compact SAW filter architecture

Inventive Principle:

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

Solution Approach 2:

The patent introduces intermediary resonators as mediator elements between the input and output of the SAW filter. These resonators act as intermediate signal paths that specifically target and suppress bulk mode responses at critical frequencies, allowing the main signal to pass through while blocking the harmful bulk mode leakage

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If surface acoustic wave filters are used, then chip size and cost are reduced, but signal leakage increases due to bulk mode responses

Engineering Contradiction:

Improvechip sizeVSAvoidsignal leakage

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

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

Solution Approach 2:

The patent applies local quality by positioning resonators with specific characteristics (different orientations, different resonant frequencies) at specific locations within the filter structure. Each resonator is locally optimized to suppress bulk mode responses at particular frequencies and locations, creating a distributed suppression strategy that effectively reduces signal leakage across the entire frequency spectrum

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 configuration effectively reduces ripple in insertion loss and suppresses signal leakage, enabling surface acoustic wave filters to meet performance specifications with smaller chip size and reduced cost compared to bulk acoustic wave filters.

Implementation Method 1

surface acoustic wave resonators configured to filter a radio frequency signal

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Implementation Method 2

The circuit element and the first surface acoustic wave resonator have different resonant frequencies

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS12489427B2Filter including acoustic wave resonator in parallel with circuit element

Publication Date: 2025.12.02 SKYWORKS SOLUTIONS INC

AI summary

Aspects of this disclosure relate to an acoustic wave filter that includes acoustic wave resonators arranged to filter a radio frequency signal. The acoustic wave resonators include a first acoustic wave resonator. The acoustic wave filter includes a circuit element in parallel with the first acoustic wave resonator in a stage of the acoustic wave filter. The circuit element and the first acoustic wave resonator have different resonant frequencies. The circuit element can reduce an impact of bulk mode of the first acoustic wave resonator on insertion loss of the acoustic wave filter. The first acoustic wave resonator can be a surface acoustic wave resonator in certain embodiments. The circuit element can be a second acoustic wave resonator or a capacitor, for example.