Optical Waveguide EMI Shield for Circuit Boards

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Solution Overview

Problem

Existing EMI shielding techniques for circuit boards are inadequate in protecting susceptible circuits from high-frequency electromagnetic interference (up to 40 GHz) while allowing signal transmission between these circuits and external devices.

Innovation Solution

Integration of electromagnetic waveguides and optical waveguides on circuit boards, where the electromagnetic waveguides attenuate unwanted electromagnetic fields below a desired cutoff frequency, and optical waveguides enable signal transmission through the shield, allowing communication between EMI-sensitive electronics and external devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If traditional EMI shielding techniques are used to protect susceptible circuits from high-frequency EMI, then EMI protection is improved, but signal transmission capability deteriorates

Engineering Contradiction:

ImproveEMI protectionVSAvoidsignal transmission

Core Design Contradiction:

Object-affected harmful factorsVSLoss of information

Solution Approach 1:

The patent divides the waveguide structure into multiple segments including EMI-shielding waveguide sections and optical signal transmission waveguide sections. This segmentation allows different portions of the same physical structure to perform different functions: blocking EMI while permitting optical signals to pass through, thereby resolving the contradiction between EMI protection and signal transmission.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different material properties and structural characteristics to different regions of the waveguide. The EMI-shielding portions use conductive materials and geometric configurations optimized for blocking electromagnetic fields, while the optical transmission portions use materials and structures optimized for light propagation. This local differentiation enables simultaneous EMI protection and signal transmission.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If susceptible circuits are placed far from EMI generating circuits, then EMI protection is improved, but device complexity increases

Engineering Contradiction:

ImproveEMI protectionVSAvoidcircuit design constraints

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary waveguide structure between the EMI-generating circuits and susceptible circuits. This waveguide acts as a mediator that allows necessary signal and power transmission while blocking harmful EMI. The intermediary structure enables close placement of circuits without direct EMI coupling, simplifying the overall circuit design by removing the need for large separation distances.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If separate card assemblies are used for susceptible circuits, then EMI protection is improved, but manufacturing complexity increases

Engineering Contradiction:

ImproveEMI protectionVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent merges the EMI-shielding function and optical signal transmission function into a single integrated waveguide structure that is incorporated directly into the circuit board. This consolidation eliminates the need for separate card assemblies while maintaining EMI protection. The integrated approach simplifies manufacturing by reducing the number of discrete components and assembly steps required.

Inventive Principle:

Principle #5Merging (Combining)

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 provides effective high-frequency EMI shielding with compact circuit board designs, removing placement constraints and enhancing EMI protection while enabling signal transmission, resulting in improved circuit board assembly performance.

Implementation Method 1

at least one electro-magnetic (EM) waveguide configured to attenuate and prevent electro-magnetic fields below a desired cutoff frequency from interfering with operation of electro-magnetic interference (EMI) sensitive circuit board electronics below the desired cutoff frequency

Methodology Applied

Scientific EffectElectromagnetic waveguide attenuation: Waveguide

Implementation Method 2

at least one optical waveguide configured to pass optical signals transmitted to and from the EMI sensitive circuit board electronics, the optical signals passing through both the at least one optical waveguide and the at least one electro-magnetic waveguide at frequencies below the desired cutoff frequency

Methodology Applied

Scientific EffectOptical waveguide transmission: Waveguide (optics)

Data Source

PatentUS7912328B2Optical waveguide EMI shield

Publication Date: 2011.03.22 GENERAL ELECTRIC CO

AI summary

A circuit board assembly is configured to attenuate and prevent electro-magnetic fields from interfering with operation below a desired cutoff frequency, of electro-magnetic interference (EMI) susceptible circuit board electronics disposed within a shielded enclosure, while allowing signals to be transmitted between the EMI susceptible circuit board electronics at frequencies below the desired cutoff frequency, and circuits or devices external to the shielded enclosure.