Electromagnetic and RF Shielding

Premier Security Ballistic & Blast Ltd provides electromagnetic and RF shielding for buildings, rooms, enclosures and equipment, from modular Faraday cages and anechoic chambers through to whole building architectural shielding and magnetic field control.

Electromagnetic shielding solves two problems that look identical in construction terms but arrive from opposite directions. In one case interference is getting in and disrupting sensitive equipment. In the other, emissions are getting out and creating a compliance failure, a test invalidity or a security exposure. The same conductive envelope answers both, and the design work lies in deciding how much attenuation is needed, across which frequency range, and at what cost.

How Electromagnetic Shielding Works

A shield is a continuous conductive envelope placed between a source of electromagnetic energy and the area to be protected. Energy striking the envelope is reflected, absorbed and dissipated rather than passing through, and the completeness of the envelope matters more than the thickness of any single part of it.

This is why apertures dominate shielding design. A well specified panel system delivers very little if the door gasket has degraded, the ventilation opening is untreated or a cable enters unfiltered. Every penetration must be resolved to a performance equivalent to the surrounding material, which is why doors, windows, vents, filters and pipe penetrations are engineered as part of the shield rather than fitted into it afterwards.

Modular Shielded Rooms and Faraday Cages

We provide a turnkey service covering the design, fabrication and installation of modular shielded rooms, EMC chambers and anechoic chambers.

Modular shielded rooms, also referred to as modular Faraday cages, are constructed from prefabricated 2 mm galvanised sheet steel panels. Panels are bolted together with an electrically conductive mesh gasket placed between every joint, which maintains continuity of the shield across the whole envelope while keeping the structure demountable and relocatable. The approach allows almost unlimited size and configuration options and delivers high shielding performance alongside long term corrosion resistance.

Rooms are completed with shielded doors, shielded windows, pipe penetrations and RF filters. Internal fit out is specified to suit the end use, ranging from a conventional office type interior through to microwave absorber linings forming a semi anechoic or fully anechoic chamber. Full lighting and electrical distribution can be provided within the room.

Shielded Cabinets and Containers

Where the requirement is to protect specific equipment rather than an occupied space, cabinet and container scale shielding is usually the more cost effective route.

Modular shielded cabinets can be configured to any size from desktop through to walk in, with filters, telephone and data filtering, ventilation, power distribution and thermal insulation incorporated as required. Racking for internal equipment, shock mounts and wheels can be accommodated where the unit needs to be serviceable or mobile.

Shielded containers extend the same principle to a deployable format. ISO containers have long since outgrown shipping and now serve as communications shelters and site accommodation, and where those roles carry an electromagnetic requirement the container itself becomes the shield. Options range from a shielded shell through to a fully fitted unit with internal linings, lighting, furniture and air conditioning.

RF Shielded Doors

The door is the most important element of any shielded facility. It is the largest moving aperture in the envelope, its performance depends on a contact system that must reseat correctly every time it closes, and it is the component most exposed to wear over the life of the building.

We provide RF shielded doors across all performance levels and applications, internal and external, including doors for mobile containers and anechoic chambers. Where an opening has to satisfy more than one requirement, doors can be specified to combine RF shielding with fire resistance and with thermal, acoustic, NBC and blast protection. Because shielding projects are rarely identical, designs are adapted to the specific opening, operational pattern and threat profile.

Each additional performance requirement must be evidenced by its own testing. A door that attenuates to a given level is not thereby fire rated, and a fire rated door is not thereby shielded.

Windows, Vents, Filters and Penetrations

The apertures determine the achieved performance, and each one has an established treatment.

Shielded Windows

Shielded viewing windows use layered blackened mesh to deliver attenuation matching the surrounding envelope while retaining usable visibility. Mesh layers must be set at a precise relative angle to avoid the visual distortion known as Fresnel interference. Windows are available in a range of sizes and frame designs, with or without mullions.

Waveguide Vents

Waveguide vents are a critical component of any shielded building, room or enclosure. A steel or aluminium honeycomb construction allows air to pass through while attenuating radiated interference, which is what makes a sealed conductive envelope habitable and thermally viable. Vent sizing sits at the interface between the mechanical services design and the shielding specification, and is best resolved early.

RF Filters and Pipe Penetrations

Every power, data and signal conductor crossing the shield boundary must be filtered, or it will carry interference straight through an otherwise sound envelope. Filters are selected against the current rating, voltage, frequency and attenuation requirement of each individual circuit. Pipework and fibre optic entries are treated through dedicated penetration assemblies that maintain electrical continuity across the boundary.

Architectural Shielding

As the density of electrical and electronic equipment in buildings continues to rise, the interference generated by emitted electromagnetic fields increasingly has to be addressed at building level rather than room by room. Architectural shielding protects the structure and everything housed within it using shielding materials bonded directly to the host building.

Commonly used materials include heavy duty copper and aluminium foils at 0.125 mm thickness, and steel sheet. Selection is driven by the required attenuation, the frequency range over which it must be achieved, and cost. Careful design and treatment of apertures is what determines whether the installed system reaches the practical maximum performance the chosen material is capable of.

Most projects arrive without a defined attenuation specification. Where that is the case, an initial site survey quantifies background field strengths so that an appropriate and testable attenuation target can be set before any material is committed.

Power Frequency Magnetic Field Shielding

Power frequency magnetic fields, or PFMF, are generated by electrical distribution systems, electromagnets and electric motors, and can create problems for both equipment and occupants. Where these fields need to be contained or controlled, shielding places a physical barrier of appropriate material between the source and the affected area. Steels are the most commonly used materials.

PFMF shielding works by diverting and deflecting the field away from the affected area rather than absorbing it. This has a practical consequence that catches out inexperienced designs: a magnetic field will flow around a partial shield. Because these fields decay rapidly with distance, the physical extent of the shield has to be large enough to account for that behaviour. The single most critical design criterion is the level of attenuation required.

Solutions cover SEM and TEM shielding, AC and DC magnetic field shielding and 50/60 Hz magnetic field shielding. Our services include input during the preliminary shielding design phase, electromagnetic field surveys and pre-installation studies, remedial proposals for existing installations, and the design and installation of the shielding solution itself.

Technical advice should be sought at planning stage wherever possible. Magnetic interference is considerably cheaper to design out than to retrofit around.

Data Centre Shielding

Data centres carry an unusual combination of exposure. As the storage and processing backbone for both commercial and government operations, they are scrutinised heavily on security, availability and standards compliance, yet the electromagnetic threat is frequently absent from that assessment.

Electronic eavesdropping is one route, and it is insidious precisely because a successful interception leaves no indication that it has occurred. For most commercial applications encryption addresses that adequately. The more serious exposure is to electromagnetic surges, whether from a nuclear electromagnetic pulse or from a deliberate non-nuclear device such as a Marx generator, a category known as Intentional Electromagnetic Interference or IEMI. Damaging currents and extremely high voltage surges can disrupt or completely destroy data processing and storage systems.

We provide protection against both conducted and radiated electromagnetic interference, integrated with the building fabric and with every service entering the facility, alongside testing services to identify weaknesses in existing host rooms and buildings.

Specification, Survey and Testing

Wherever possible a project should carry a defined specification stating the required shielding attenuation across a stated frequency range. In practice that information is rarely available at the outset, and writing an arbitrary figure into a specification is worse than writing none at all.

• Initial site surveys to quantify background field strengths and establish an appropriate attenuation target
• Input during the preliminary shielding design phase, before construction detailing is fixed
• Pre-installation studies on electromagnetic field effects
• Design, supply and installation of the shielding solution
• Final attenuation testing on completion to demonstrate conformance with the original specification
• Remedial assessment and proposals for existing shielding installations that are underperforming

Final attenuation testing is the only point at which specified performance is confirmed to have been achieved, and we recommend it is written into the specification as a witnessed acceptance activity rather than a self certification exercise.

Sectors We Support

• Defence establishments and military communications facilities
• Government estates and command and control centres
• Data centres and government and defence-adjacent compute facilities
• EMC test houses, laboratories and research establishments
• Healthcare and diagnostic imaging
• Telecommunications and broadcast infrastructure
• Industrial and manufacturing premises with clean test area requirements
• Commercial and residential developments adjacent to distribution infrastructure

Electromagnetic Shielding FAQs