Theory, design and perspectives of electromagnetic wave absorbers

Electromagnetic absorbers for free space and cavity absorption are discussed. Classical configurations are described as well as more recent designs. The presented layouts are able to provide absorbing behaviors spanning from ultra-narrow band to ultra-wideband. A comparison among various solutions is presented both in terms of achievable bandwidth and in terms of minimum theoretical thickness. The problem of cavity resonances is also addressed. It is shown that resonances can be damped by using alternative solutions with respect to the classic use of lossy magnetic materials.