Lateral Multi-Piezoelectric BAW Resonator for Harmonic Suppression

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Solution Overview

Problem

Suppression of non-linearity and harmonic distortion in bulk acoustic wave (BAW) resonators, particularly in high power applications, is a technical challenge that affects radio frequency systems, leading to harmonic emission and receiver de-sensing.

Innovation Solution

A BAW device with multiple piezoelectric layers positioned laterally between electrodes, where the layers have different properties such as c-axis orientation or doping concentration, are connected in parallel to suppress second harmonic distortion and enhance out-of-band rejection without additional parasitics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple BAW resonators are used to achieve strong out-of-band rejection, then rejection performance is improved, but device area and parasitics increase

Engineering Contradiction:

Improveout-of-band rejectionVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines multiple piezoelectric layers (first, second, and third layers) within a single BAW resonator structure, where each layer contributes to different rejection frequencies. This merging approach achieves the out-of-band rejection of multiple resonators while using a single resonator footprint, thereby reducing device area and minimizing inter-resonator parasitics.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs composite piezoelectric layer structures with different materials or properties (e.g., AlN, ScAlN, or other piezoelectric materials) to create a multi-functional resonator. Each layer can be tailored to provide specific acoustic impedance and resonance characteristics, enabling multiple rejection frequencies within one resonator.

Inventive Principle:

Principle #40Composite materials

2Power

If high power is applied to BAW resonators, then output power is improved, but harmonic distortion increases

Engineering Contradiction:

Improveoutput powerVSAvoidharmonic distortion

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful second harmonic distortion into a beneficial cancellation mechanism. By designing the second piezoelectric layer with specific properties (different material, thickness, or acoustic impedance) and positioning it to generate second harmonic distortion that is 180 degrees out of phase with the first layer, the harmful distortion products cancel each other out, enabling high power operation with reduced harmonic emission.

Inventive Principle:

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

Solution Approach 2:

The patent changes key parameters of the piezoelectric layers including material composition (e.g., AlN vs. ScAlN), thickness, and acoustic impedance to optimize the cancellation of harmonic distortion. By carefully controlling these parameters, the resonator achieves both high power handling and low distortion performance.

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If piezoelectric layers are added to suppress harmonic distortion, then distortion suppression is improved, but device complexity increases

Engineering Contradiction:

Improveharmonic distortionVSAvoiddevice complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments the piezoelectric functionality into multiple distinct layers, each with specific roles. The first piezoelectric layer provides primary resonance, while the second and third layers are specifically designed for harmonic distortion cancellation. This segmentation allows for modular design and optimization of each layer's properties.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent achieves multi-functionality within a single BAW resonator structure. The same resonator that provides the primary acoustic resonance also simultaneously cancels second harmonic distortion through its multi-layer piezoelectric structure, eliminating the need for separate distortion cancellation circuits or additional resonators.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively suppresses second harmonic distortion and achieves strong out-of-band rejection with reduced area consumption and parasitics, meeting stringent rejection specifications with fewer resonators.

Implementation Method 1

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

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

acoustic waves propagate in a bulk of a piezoelectric layer

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 3

BAW resonators include film bulk acoustic wave resonators (FBARs) and BAW solidly mounted resonators (SMRs)

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20250392284A1Acoustic wave device having multiple piezoelectric layers between electrodes

Publication Date: 2025.12.25 SKYWORKS SOLUTIONS INC

AI summary

Aspects of this disclosure relate to an acoustic wave device with a plurality of piezoelectric layers positioned laterally relative to each other between two electrodes. One of the piezoelectric layers has a different property than another of the piezoelectric layers. Examples of the different property include c-axis orientation, doping concentration, dopant material, and piezoelectric material. At least part of each of the piezoelectric layers can be in a main acoustically active region of the acoustic wave device.