Anechoic Chambers
Shielded Chambers,
Screened Rooms
& Faraday Cages
Anechoic Absorbers
Shielding materials & shielding components

The facts about Block Absorbers

Block Absorbers
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Global EMC... Block Absorbers
The Global EMC block absorber is a single carbon doped foam. This product is often used in the corners of anechoic chambers to prevent reflective surfaces.
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Block absorbers are normally Carbon doped foam blocks for EMC and other radiated electromagnetic absorbing applications. There are tuned film type block absorbers but they are seldom used.


There are two types of block absorber:


  1. Single or ‘mono-doped’ block
  2. Multi-layered or laminated block

Type 1

Mono-doped block absorber

This product can be made in various thicknesses (50mm and 75mm are common) and is normally painted finished on 5 sides in blue or white. Mono doped block absorber is normally used for:


  1. The corners of anechoic chambers
  2. Other experimental EMC tests

The absorbing performance (return loss) of the mono-doped block is not an issue because the product has no definitive function, that is, mono-doped absorber is only for general non-critical use but will give some absorbing performance.


Mono-doped absorber is relatively low cost compared to layered/laminated block products.


Type 2

Layered or laminated Block absorber

This absorber is constructed from layers of thin absorbers glued together, these absorbers are normally painted on 5 sides with the base of the absorber being unpainted.

The doping of the layers are graded so that the outer layer is the least doped with the most doped layer at the base of the block.


Thickness normally range from 10mm up to 100mm, the thinner products have reduced effect at low frequencies, there can be as low as 2 layers and as many as 5 layers. The radio wave/microwave first encounters the outer less doped layer and then a more doped layer and so on.


The performance of the absorber in term of return loss is not as good as pyramidal absorber because pyramidal absorber attains progressive impedance (performance) through it’s shape as well as it’s loading whereas the Layered/laminated block absorber has a number of ‘step function’


Applications

Layered absorber is ideal for EMC product use as the multi reflections inside a product make the layered absorber very effective at electromagnetic (EMI) suppression and takes little space compared with pyramidal foam.


The 100mm thick product can also be used in anechoic chambers for experimental work.