Aircraft Nacelle Gap EBG Shielding for EMI Filtering

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Solution Overview

Problem

Aircraft electronics are susceptible to electromagnetic interference (EMI) due to gaps in the aircraft structure, which current protective conductive seals are not effective against, and these seals are costly and difficult to maintain.

Innovation Solution

An electromagnetic band gap (EBG) structure is integrated into the aircraft's airframe near gaps, comprising a broadband high-impedance surface with unit cells including a metal ground plane, patches, and conducting vias, which filters out penetrating electromagnetic energy and prevents resonant cavity mode build-ups, effectively shielding internal electronics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If protective conductive seals are used to shield gaps, then EMI protection is provided, but cost and maintenance difficulty increase

Engineering Contradiction:

ImproveEMI protectionVSAvoidcost and maintenance

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical conductive seals with an electromagnetic field-based solution using EBG structures. These structures create high surface impedance through electromagnetic resonance effects, eliminating the need for physical contact seals while providing superior EMI protection across broadband frequencies.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the fundamental parameter from conductive material properties to electromagnetic impedance properties. By designing EBG unit cells with specific geometric parameters (patch dimensions, via positions, substrate thickness), the structure achieves high surface impedance over broadband frequencies, providing EMI protection without the limitations of conductive seals.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If conductive seals are installed in gap locations, then some EMI protection is achieved, but effectiveness against all electromagnetic penetrations is insufficient

Engineering Contradiction:

ImproveEMI protection effectivenessVSAvoidprotection completeness

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The EBG structures provide universal EMI protection across multiple frequency ranges and penetration mechanisms. The periodic structure creates stop-bands for electromagnetic waves through Bragg scattering and resonance effects, effectively blocking both surface waves and direct penetrations without relying on gap sealing, thus protecting against all types of electromagnetic threats.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention uses composite EBG structures combining conductive patches, via holes, and dielectric substrates to create a multi-layered electromagnetic barrier. This composite structure leverages the complementary strengths of different materials and geometric features to achieve broadband EMI suppression that single-material seals cannot provide.

Inventive Principle:

Principle #40Composite materials

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 EMI shielding assembly significantly reduces electromagnetic radiation penetration, protecting avionic systems by blocking surface waves over a specific frequency range, as demonstrated by a substantial drop in electric field intensity from exterior to interior, enhancing the protection against EMI and RFI.

Implementation Method 1

Methodology Applied

Scientific EffectElectromagnetic band gap:

Implementation Method 2

The EBG structure... filters out penetrating electromagnetic energy and prevents resonant cavity mode build-ups, effectively shielding internal electronics

Methodology Applied

Scientific EffectElectromagnetic filtering: Filter (electronic)

Implementation Method 3

comprising a broadband high-impedance surface with unit cells including a metal ground plane, patches, and conducting vias

Methodology Applied

Scientific EffectHigh-impedance surface:

Implementation Method 4

prevents resonant cavity mode build-ups

Methodology Applied

Scientific EffectElectromagnetic resonance: Resonance

Data Source

PatentEP4462971A1Radio frequency filter for aircraft nacelle access door gap

Publication Date: 2024.11.13 THE BOEING CO

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AI summary

An assembly for electromagnetic interference (EMI) shielding to prevent incident radiation from penetrating through a gap to an interior of an aircraft comprises an electromagnetic band gap (EBG) structure. The EBG structure has a patch-and-via array connected to a ground layer. The EMI shielding includes a conductive adhesive and is flexible for conforming attachment to curved aircraft surfaces. The shielding may be located on a deflector plate that is parallel to an adjacent aircraft surface, on the airframe surface opposite to the deflector plate, or in both locations. The assembly filters out penetrating electromagnetic energy and prevents highly resonant cavity mode buildups of electromagnetic energy inside a nacelle or other enclosure effectively protecting electrical equipment in the interior.