Microwave Absorbers: Material and Absorber Types

Microwave absorbers are materials used for the absorption or reduction of unwanted radiations found in a microwave. You can use them in applications where stray and harmful electromagnetic waves interfere with other electronic devices, components, systems, and machinery. Use microwave absorbers internally or externally depending on your requirement. If you are going for internal usage, it involves the attenuation of oscillations due to cavity resonance. External usage, on the contrary, entails the reduction of wave reflection. Microwave absorbers come in diverse forms including plastics, foam, elastomer products, and rigid epoxy. These materials have the ability to endure extreme weather and temperature conditions. Read on to learn more about absorber material and types.

Wide Range of Materials

You can use different absorber materials for reducing electromagnetic interference (EMI) and radar cross section (RCS). If you want to optimize absorber use in a particular design, you will need to examine three main parameters such as physical, electrical, and application. Microwave absorbers come with a material-matrix that’s filled with different material types. The filler materials used have the ability to absorb the electromagnetic waves. The choice of material depends on the kind of physical properties you have in mind. For instance, if you want an absorber with excellent temperature resistance, you will need to choose a material resistant to extreme temperature conditions. In some of the situations, you may need to mix materials to achieve the required balance of two or more physical properties. You can choose absorbers based on their electric permittivity and magnetic permeability. These categorizations determine a material’s ability to reduce harmful emissions.

Types of Absorbers

There are two kinds of microwave absorbers used for outdoor and protected environments. They are:

Elastomeric absorbers: These products are best suited for outdoor use. You can use them as an adhesive bonding to any metal surface. The bonding agents vary depending on the kind of elastomer you choose and include urethanes, epoxies, pressure-sensitive adhesives, and contact adhesives. Normally, nitrile and Hypalon are the common elastomers that bond easily and come with a number of compatible adhesive systems. Choose bond strengths of more than 10 pounds for every inch for better performance. Sometimes, you may need to cover an intricate curve or tight radius. You can choose flat sheet materials that are conformally molded components. These conformal molds make the process of bonding simpler as well as reduce the possibility of any built-in stresses into the substance. If you are using gasket applications, the elastomer rubber may extrude. You will need to paint the absorber for enhanced weather resistance. To fill up the openings between the sheets, use absorptive gap fliers to reduce impedance disparity in the sheets. This method also controls the formation of reflections and surface waves. For corrosive surroundings, you can opt for a non-corrosive filler material like iron silicide.

Broadband absorbers: These absorbers are used in a confined environment such as in nacelles or radomes. The application technique is adhesive bonding, and you can use a broad range of adhesives such as epoxies, contact cement, and acrylic pressure-sensitive bonding agents. You can ask your EMI shielding material supplier to paint the front surfaces for additional absorber protection.

Use microwave absorbers based on their physical, application, and electrical parameters. Engineers should consider factors like resonance reduction, insertion and reflection loss, surface wave attenuation, environment, coverage area, and frequency band while designing absorbers.

Elvis Moore is an active blogger with an extensive industry experience in the field of electronics and technology.