Microwaves cavities are often designed as short-end or slotted waveguides, such circuits tend to create unwanted radiating fields. The radiating fields inside the enclosure will act as standing waves with electric and magnetic components. By installing absorber material on the side of a waveguide circuit or on walls of a cavity the electromagnetic energy in these enclosures will be suppressed and improve the Q-factor.
In most cases a magnetically loaded absorber material is applied in the enclosures, however in larger systems also dielectric loaded foam absorber is used to reduce resonances inside a cavity. Standing waves are difficult to detect, define and suppress, also selecting the most effective absorber material is difficult. RF-simulation software is sometimes able to define a solution, still we advise to evaluate different absorber types.