Grid-Structured BAW Resonator for Spurious Mode Suppression

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Solution Overview

Problem

Current bulk acoustic wave resonators face challenges in improving communication quality due to spurious modes that affect the performance of filters in mobile communication systems, particularly in high-frequency bands like N77, where the electromechanical coupling coefficient is insufficient to meet bandwidth requirements.

Innovation Solution

The design incorporates a bulk acoustic wave resonator with a piezoelectric material layer, comb-shaped electrodes, and a grid structure that suppresses high-order mode excitation by disrupting the periodicity of acoustic wave propagation, enhancing the electromechanical coupling coefficient and eliminating spurious modes through specific electrode finger spacings and grid structure arrangements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional bulk acoustic wave resonator structure is used, then the device is simple to manufacture, but spurious modes are excited and the electromechanical coupling coefficient is insufficient

Engineering Contradiction:

Improvefilter performanceVSAvoidresonator structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The resonator structure is segmented by introducing a grid structure that divides the acoustic wave propagation path into multiple sections. This segmentation disrupts the periodicity that causes spurious modes while maintaining the overall resonator function, thereby improving filter performance without requiring complete structural redesign

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A grid structure is introduced as an intermediary element between the electrodes and the acoustic wave propagation path. This grid structure acts as a mediator that suppresses spurious modes by disrupting periodicity, allowing the resonator to achieve better filter performance while maintaining a manageable structural complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the electromechanical coupling coefficient is increased to meet bandwidth requirements, then high-frequency band performance improves, but spurious modes are more strongly excited

Engineering Contradiction:

Improvebandwidth capabilityVSAvoidspurious modes

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The grid structure is designed to convert the harmful periodicity-induced spurious modes into a beneficial non-periodic pattern. By strategically placing the grid, the structure transforms what would be harmful resonant periodicity into a pattern that suppresses spurious modes while allowing the electromechanical coupling coefficient to be increased for better bandwidth capability

Inventive Principle:

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

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 significantly improves the electromechanical coupling coefficient, effectively suppressing spurious modes and enhancing the resonator's performance to meet the demands of high-frequency bands, such as the N77 band, by maximizing the main mode excitation intensity and expanding the regulation range of the coupling coefficient.

Implementation Method 1

a piezoelectric material layer, a first comb-shaped electrode, a second comb-shaped electrode... The first comb-shaped electrode is disposed on the piezoelectric material layer... The second comb-shaped electrode is disposed on the piezoelectric material layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The grid structure is disposed at least between the first electrode finger and the second electrode finger, and is configured to suppress excitation of a high-order mode when an acoustic wave propagates along a first direction... the grid structure disposed between the first electrode finger and the second electrode finger can damage a periodicity of the acoustic wave propagating in the piezoelectric material layer along the first direction

Methodology Applied

Scientific EffectAcoustic wave propagation disruption: Acoustic Absorption

Data Source

PatentUS20240322787A1Bulk acoustic wave resonator, filter, and electronic device

Publication Date: 2024.09.26 HUAWEI TECH CO LTD

AI summary

A bulk acoustic wave resonator comprises a piezoelectric material layer, a first comb-shaped electrode, a second comb-shaped electrode, and at least one grid structure. The first comb-shaped electrode is disposed on the piezoelectric material layer, and the first comb-shaped electrode includes a first busbar and a plurality of first electrode fingers sequentially arranged along an extension direction of the first busbar. The second comb-shaped electrode is disposed on the piezoelectric material layer, and the second comb-shaped electrode includes a second busbar and a plurality of second electrode fingers sequentially arranged along an extension direction of the second busbar. The plurality of first electrode fingers and the plurality of second electrode fingers are arranged at spacings and do not contact each other. The grid structure is disposed at least between the first electrode finger and the second electrode finger.