Anechoic Chamber

Anechoic Chambers and Absorbing materials for antenna and Electromagnetic Compatibility (EMC) Testing and RF shielding. 

The Anechoic Chambers are used to perform compliant radiated immunity tests in accordance to EMC-standards such as IEC / EN 61000-4-3. 

They provide a full compliance immunity test site for the frequency range of 26Mhz to 18GHz. Also suitable for future free space emission test, PREN 50147-3. 

We can also build open area test sites.

Emission Performance – 26MHz-18GHz

Immunity 26 MHz-18GHz

Key features:

• Fully compliant design to meet UKAS and FCC requirements
• All dimension are possible
• Emission performance of +/-4dB or better 30MHz-40GHz frequency range
• Fully compliant for Immunity in accordance with EN61000.4.3
• Ferrite and Hybrid Lining from 30MHz-40GHz measurements
• Very cost-effective solution
• Flexible modular design enables you to make easy site changes or upgrades

Turnkey Systems:

A complete system approach is available to fully facilitiate your laboratory and includes:

• Electrical distribution
• Turntables/Dynomometers
• Masts
• CCTV
• Air conditioning
• Fire detection and Surpression
• Emission & Immunity Measurement Systems

Full anechoic chambers aim to absorb energy in all directions. 

The RF anechoic chamber is typically used to house the equipment for performing measurements of antenna radiation patterns, electromagnetic compatibility (EMC) and radar cross section measurements. Testing can be conducted on full-scale objects, including aircraft, or on scale models where the wavelength of the measuring radiation is scaled in direct proportion to the target size. Coincidentally, many RF anechoic chambers which use pyramidal RAM also exhibit some of the properties of an acoustic anechoic chamber, such as attenuation of sound and shielding from outside noise.

Radiation Absorbent Material (RAM)

The RAM is designed and shaped to absorb incident RF radiation (also known as non-ionising radiation), as effectively as possible, from as many incident directions as possible. The more effective the RAM is the less will be the level of reflected RF radiation. Many measurements inelectromagnetic compatibility (EMC) and antenna radiation patterns require that spurious signals arising from the test setup, including reflections, are negligible to avoid the risk of causing measurement errors and ambiguities.

One of the most effective types of RAM comprises arrays of pyramid shaped pieces, each of which is constructed from a suitably lossy material. To work effectively, all internal surfaces of the anechoic chamber must be entirely covered with RAM. Sections of RAM may be temporarily removed to install equipment but they must be replaced before performing any tests. To be sufficiently lossy, RAM can neither be a good electrical conductor nor a good electrical insulator as neither type actually absorbs any power. Typically pyramidal RAM will comprise a rubberized foam material impregnated with controlled mixtures of carbon and iron. The length from base to tip of the pyramid structure is chosen based on the lowest expected frequency and the amount of absorption required. For low frequency damping, this distance is often 24 inches, while high frequency panels are as short as 3–4 inches. Panels of RAM are installed with the tips pointing inward to the chamber. Pyramidal RAM attenuates signal by two effects: scattering and absorption. Scattering can occur both coherently, when reflected waves are in-phase but directed away from the receiver, or incoherently where waves are picked up by the receiver but are out of phase and thus have lower signal strength. This incoherent scattering also occurs within the foam structure, with the suspended carbon particles promoting destructive interference. Internal scattering can result in as much as 10 dB of attenuation. Meanwhile, the pyramid shapes are cut at angles that maximize the number of bounces a wave makes within the structure. With each bounce, the wave loses energy to the foam material and thus exits with lower signal strength.

An alternative type of RAM comprises flat plates of ferrite material, in the form of flat tiles fixed to all interior surfaces of the chamber. This type has a smaller effective frequency range than the pyramidal RAM and is designed to be fixed to good conductive surfaces. It is generally easier to fit and more durable than the pyramidal type RAM but is less effective at higher frequencies. Its performance might however be quite adequate if tests are limited to lower frequencies (ferrite plates have a damping curve that makes them most effective between 30–1000 MHz).

There is also a hybrid type, a ferrite in pyramidal shape. Containing the advantages of both technologies, the frequency range can be maximized while the pyramid remains small (10 cm).

Anechoic chambers are commonly used in acoustics to conduct experiments in nominally "free field" conditions. All sound energy will be traveling away from the source with almost none reflected back. Common anechoic chamber experiments include measuring the transfer function of a loudspeaker or the directivity of noise radiation from industrial machinery. In general, the interior of an anechoic chamber is very quiet, with typical noise levels in the 10–20 dBA range. 

Semi-anechoic chambers have a solid floor that acts as a work surface for supporting heavy items, such as cars, washing machines, or industrial machinery, rather than the mesh floor grille over absorbent tiles found in full anechoic chambers. This floor is damped and floating on absorbent buffers to isolate it from outside vibration or electromagnetic signals.