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What are Microwave Absorbers?

10/31/2013 4:13:09 PM | by Anonymous

Microwave Absorbers

Microwave absorbers are special materials that are used to reduce or absorb the energy that is present in a microwave. Microwave absorbers are used mainly in applications where there is unwanted or stray radiation that may interfere with other machinery or electronic components. Microwave absorbers can either be used externally or internally. External usage involves the reduction of reflection of the microwaves. Where as internal usage involves the reduction of oscillations as a result of cavity resonance. Microwave absorbers may also be used to make a free space environment by using an anechoic chamber to reduce the microwaves. Microwave absorbers can come in many forms which include foam, rigid epoxy, plastics or elastomers. These microwaves absorbers are usually able to withstand extreme temperature and weather conditions.


Microwave absorbers usually have a material matrix which is filled by different kinds of material. The filler materials are usually the ones that are able to absorb the microwaves. The material that these filler material are made of usually depends on what type of physical properties is desired. For example if the microwave absorber is to have good temperature resistance, then a certain type of material is used. This applies for other physical properties as well. In some cases, the materials can be mixed to achieve a balance of two or more physical properties. Most microwave absorbers however, are classified by its magnetic permeability and electric permittivity. These classifications measure a microwave absorber’s effectiveness in absorbing microwaves.


There are basically two types of microwave absorbers that exist; they are insertion loss microwave absorbers and reflectivity microwave absorbers. Insertion loss microwave absorbers aim to reduce the microwave signals during its journey from one point to another. Reflectivity microwave absorbers on the other hand simple reflect the microwave signals.


Apart from these two main types of microwave absorbers, there are also other types. One of it is the magnetic microwave absorber. This type of microwave absorber uses ferromagnetic materials that fill the matrix. By using this type of material, it gives the microwave absorber high magnetic less and high permeability. The advantage of using ferromagnetic materials is that it is able to compress the wavelength by a large amount. This is because the high permeability enables the resonant absorbers that have absorbs the microwave to a mere fraction of its original wave length. Magnetic microwave absorbers are particularly useful for absorbing microwaves in applications where there is a magnetic field present.

 

The downside of magnetic microwave absorbers is that they are very heavy compared to other types of microwave absorbers and because of the filler material used they can be quite expensive as well. These materials usually come in different forms such as urethane, silicone, neoprene and nitrile. The matrix material varies form rigid epoxy or foams to try and reduce its weight.


Another type of microwave absorber is the dielectric microwave absorber. This type of microwave absorber does not possess any magnetic properties at all. Such absorbers use dielectric mechanisms to absorb the microwaves, hence its name. Compared to the magnetic microwave absorber, dielectric absorbers are much cheaper and lighter. However, dielectric microwave absorbers have high electrical conductivity. This limits their usage as they are unable to come into conduct with electronic components. Dielectric microwave absorbers also suffer a loss in performance due to their lack in magnetic properties.


Most microwave absorbers are able to be molded into different forms to suit different applications. This includes two liquids that are mixed together and solidify at room temperature. The mold can also be injected with pellets and melted once it is in the matrix. Overall, microwave absorbers have been very useful in protecting machinery from harmful radiation caused by microwaves.

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