BAW Resonator Air-Gap Layout for Second Harmonic Suppression

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Solution Overview

Problem

Bulk acoustic wave resonators exhibit non-linearity at high power levels, leading to unwanted second harmonic emissions that can desensitize receiver systems in wireless communication applications, particularly in filters like film bulk acoustic wave resonator (FBAR) filters.

Innovation Solution

The implementation of anti-series connected bulk acoustic wave resonators with an air gap between the conductor and the substrate to reduce parasitic capacitance, thereby suppressing second harmonic emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If bulk acoustic wave resonators are used at high power levels, then the filter can handle high power signals, but second harmonic emissions increase causing non-linearity

Engineering Contradiction:

Improvepower handling capabilityVSAvoidsecond harmonic emissions

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an air gap between the conductor and substrate, converting the harmful parasitic capacitance into a beneficial low-capacitance structure. The air gap's low dielectric constant reduces parasitic capacitance, which in turn reduces second harmonic emissions while maintaining power handling capability, effectively turning a potential source of non-linearity into a solution for harmonic suppression

Inventive Principle:

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

2Volume of moving object

If the conductor is positioned close to the substrate, then the device size is reduced, but parasitic capacitance increases leading to second harmonic emissions

Engineering Contradiction:

Improvedevice sizeVSAvoidparasitic capacitance

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent changes the dielectric parameter by introducing an air gap with low dielectric constant between the conductor and substrate. This parameter change reduces parasitic capacitance without significantly increasing device volume, as the air gap occupies minimal space while providing effective capacitance reduction to suppress second harmonic emissions

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

This configuration effectively cancels second harmonic power emissions by up to 30 decibels, improving the linearity of the filter and meeting stringent harmonic and intermodulation distortion specifications.

Implementation Method 1

an air gap positioned between the conductor and a surface of the substrate

Methodology Applied

Scientific EffectParasitic capacitance: Capacitance

Implementation Method 2

In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 3

acoustic waves propagate in a bulk of a piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 4

Bulk acoustic wave resonators exhibit non-linearity at high power levels, leading to unwanted second harmonic emissions

Methodology Applied

Scientific EffectSecond harmonic generation: Second Harmonic Generation

Data Source

PatentUS12184260B2Bulk acoustic wave resonator structure

Publication Date: 2024.12.31 SKYWORKS GLOBAL PTE LTD

AI summary

Embodiments of this disclosure relate to bulk acoustic wave resonators on a substrate. The bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, a conductor electrically connecting the first bulk acoustic wave resonator to the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate.