Vertical SAW Resonator Coupling for Compact RF Filters

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing surface acoustic wave (SAW) filter circuits in stacked packages face challenges in achieving efficient vertical coupling across a piezoelectric substrate, which affects filter performance and size constraints in electronic devices.

Innovation Solution

The implementation of acoustic wave (AW) filter systems with vertically coupled resonators, where interdigital transducers (IDTs) are fabricated on both sides of a piezoelectric substrate, enabling electroacoustic coupling and complex filter characteristics while reducing device size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If SAW filter circuits use traditional planar configurations, then device performance is maintained, but device size increases and space efficiency deteriorates

Engineering Contradiction:

Improvedevice sizeVSAvoidfilter performance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent transitions from traditional planar (2D) filter configurations to a three-dimensional stacked architecture where resonators are vertically coupled across multiple layers. This dimensional change allows multiple resonators to occupy the same footprint area at different heights, significantly reducing the overall device footprint while maintaining filter performance through controlled vertical coupling between layers

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If resonators are vertically stacked across piezoelectric substrate, then device size is reduced, but coupling efficiency and filter characteristics deteriorate

Engineering Contradiction:

Improvedevice sizeVSAvoidcoupling efficiency

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent introduces intermediate coupling structures including conductive vias through the substrate, dielectric layers between resonator layers, and dedicated coupling resonators that facilitate controlled energy transfer between vertically stacked resonators. These intermediaries enable precise control of coupling strength and phase relationships, ensuring high coupling efficiency despite the vertical separation between resonators

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs parameter optimization including adjusting resonator dimensions, spacing between layers, dielectric material properties, and via hole configurations to control coupling characteristics. By varying these parameters, the design achieves optimal coupling efficiency and filter response while maintaining compact vertical stacking

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If acoustic wave propagation is used, then filtering is achieved with smaller wavelength, but device complexity increases due to piezoelectric material requirements

Engineering Contradiction:

Improvefilter areaVSAvoidmaterial structure

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent uses piezoelectric substrate layers that serve multiple functions: they provide the acoustic wave propagation medium for signal filtering, act as the structural foundation for vertical stacking, and enable electromechanical coupling between electrical signals and acoustic waves. This multi-functionality reduces the need for separate components and simplifies the overall device architecture despite the specialized material requirements

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

This approach allows for the design of compact RF filters with improved performance by leveraging vertical coupling between resonators, enhancing filter selectivity and reducing space usage in electronic devices.

Implementation Method 1

Using a piezoelectric material as a vibrating medium, acoustic resonators operate by transforming an electrical signal wave, that is propagating along an electrical conductor, into an acoustic wave that is propagating via the piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The acoustic wave propagates at a velocity having a magnitude that is significantly less than that of the propagation velocity of the electromagnetic wave

Methodology Applied

Scientific EffectSurface acoustic wave propagation: Surface Acoustic Wave

Implementation Method 3

resonators on opposite sides of a piezoelectric substrate (e.g., vertically stacked resonators) can be part of the same filter, and can optionally have characteristics impacted by coupling across the piezoelectric substrate

Methodology Applied

Scientific EffectElectroacoustic coupling: Piezoelectric Effect

Data Source

PatentUS12316304B2Vertically coupled SAW resonators

Publication Date: 2025.05.27 RF360 SINGAPORE PTE LTD

AI summary

Aspects of the disclosure relate to devices, wireless communication apparatuses, methods, and circuitry implementing filters with electroacoustic vertical coupling. One aspect is a filter comprising a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite the first piezoelectric surface. The filter further comprises a first electroacoustic resonator comprising a first interdigital transducer (IDT) disposed on or over the first piezoelectric surface of the piezoelectric substrate and a second electroacoustic resonator comprising a second IDT disposed on or over the second piezoelectric surface of the piezoelectric substrate. The second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.