Reverse-Polarized BAW Resonator Layers for Noise Cancellation

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Solution Overview

Problem

Existing bulk acoustic wave (BAW) resonator devices face challenges in achieving high frequency operation and effective noise cancellation, particularly in filtering applications, due to limitations in layer thickness and parallel connection of piezoelectric films, leading to noise artifacts and degraded performance.

Innovation Solution

The introduction of a polarization-switched bulk acoustic resonator device with multiple piezoelectric film layers, where the polarities of adjacent layers are reversed, and a middle material is included to ensure series connection, allowing for improved Type II response and enhanced noise cancellation, thereby increasing operational frequency and reducing noise artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If multiple piezoelectric film layers are connected in parallel, then the resonator device can operate at higher frequencies, but noise artifacts increase and performance degrades

Engineering Contradiction:

Improveoperational frequencyVSAvoidnoise artifacts

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The resonator device is divided into multiple piezoelectric film layers (first, second, third, and fourth layers) with alternating polarities. This segmentation allows the device to operate at higher frequencies while the alternating polarity configuration enables noise cancellation, preventing the degradation that would occur with simple parallel connections.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces asymmetry through alternating polarity orientations in adjacent piezoelectric film layers. The first and third layers have one polarity orientation while the second and fourth layers have the opposite polarity. This asymmetric polarity arrangement is key to achieving both high-frequency operation and noise artifact reduction through destructive interference of unwanted modes.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If layer thickness is increased to improve resonator performance, then signal response improves, but noise artifacts are not effectively canceled

Engineering Contradiction:

Improvesignal responseVSAvoidnoise artifacts

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Instead of connecting all piezoelectric layers with the same polarity orientation, the patent inverts the polarity of alternating layers. The second piezoelectric film layer has its polarization orientation reversed relative to the first layer, and the fourth layer is reversed relative to the third layer. This inversion strategy enables noise cancellation through destructive interference while maintaining improved signal response from the increased total layer thickness.

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If simple parallel connection of piezoelectric films is used, then device complexity is reduced, but noise cancellation is ineffective

Engineering Contradiction:

Improveconnection structureVSAvoidnoise artifacts

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by giving different polarity orientations to different regions (layers) of the piezoelectric structure. Specifically, alternating layers have opposite polarity orientations, creating local variations that enable noise cancellation. This localized differentiation achieves effective noise reduction without requiring complex external connection structures, as the noise cancellation emerges from the inherent layer configuration.

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

The proposed resonator device achieves higher frequencies with reduced noise artifacts, providing improved linear performance and signal response by canceling undesired modes, making it suitable for high-frequency applications such as satellite communications.

Implementation Method 1

a first piezoelectric film layer and a second piezoelectric film layer, each having a first polarity orientation and a second polarity orientation, respectively, that are opposite one another

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

resonator devices can be used in various filtering applications pertaining to different types of signals, including filters for radio frequency (RF) signals

Methodology Applied

Scientific EffectAcoustic resonance: Resonance

Data Source

PatentUS20250337388A1Resonator devices with reverse polarized layers

Publication Date: 2025.10.30 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

An example resonator device includes a first electrode, a second electrode, a first piezoelectric film disposed between the first electrode and the second electrode, and a second piezoelectric film disposed between the first piezoelectric film and the first electrode. The first piezoelectric film has a first polarization in a first orientation, the second piezoelectric film has a second polarization in a second orientation, and the second orientation is opposite of the first orientation.