Leaded Coil Bead for EMI Shielding

Mechanical Components

RFI Shielding Methods for Chassis

Example of how to shield Radio Frequency Interference [RFI] from a chassis or metal enclosure

rfi chassis shielding feed-through methods
Signal Feed-through Methods

The graphic shows four different methods to shield incoming cables into an equipment chassis.

The first approach [top example] is to add a Feed-through capacitor [C1] at the bulk head of the chassis, and a bypass capacitor [C2].
Next a shield is added around the wire to increase the protection [shielded cable].
Than a Radio Frequency Choke [RFC] is added near the bulk-head, followed by another shunt capacitor
The last approach shown places the RFC in it's own shielded enclosure with feed-through capacitors at each end.

When feed-through capacitors are added as part of a connector, the connector is called Pin-Filtered.
However companies do produce a single-pin, capacitor filtered, bulk-head mounted feed-through to pass a signal through a metal panel.
ESD connectors have a faraday cage which protects the components inside the connector from electrostatic discharges

Feed-through capacitor definition
EMI Component Manufacturers
RFI Connector Cap Manufacturers
Capacitor Manufacturers
Military/Rugged Connector Manufacturers
Snap-On Cable Ferrite Manufacturers

Two additional approaches to reduce the effect of Electromagnetic Interference [EMI]:
Use fiber optic cable which is immune to all electrical noise.
A Twisted cable pair could be used which would cancel out the noise at the receiver, but allow the noise into the system.
Twisted Shielded cable could also be used

How to design an Electronic Chassis, manufacturers and hints
Definition of ESD terms

Design Hint; always place the ferrite bead or RF choke [in this case] near the noise source to dampen the noise as soon as possible.
Design Recommendation; Electrical connectors incorporating filter pins should be considered for use only when conventional electrical filters are not acceptable [per MIL-HDBK-454].

AC Filter Schematic for inlet power
AC Power Module Filter Schematic

If the chassis is powered from AC use an AC power module that contains an EMI filter.
Insure that the metal body of the AC module is connected to the metal frame of the chassis.

Manufacturers of AC Connectors

MIL-PRF-28861; Filters and Capacitors, Radio Frequency/Electromagnetic Interference Suppression, General Specification

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Modified 6/13/15
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