Thin absorbers: operational principles and various realizations

In this paper we discuss electrically thin absorbers: thin lossy layers which can fully absorb (convert to heat) energy of electromagnetic waves falling on the layer's surface. Most often, thin absorbers are used as covers of metal bodies, and the goal is to eliminate reflections from conducting surfaces, with applications in EMC and stealth technology. However, in some applications it is necessary to absorb power in free-standing thin layers, for example, to create optically transparent windows which can fully absorb microwave radiation in a given frequency range. The goal of this paper is to explain the fundamental operational principles of thin absorbers, discuss fundamental limitations on their performance, and give a brief overview of recent research on thin absorbers for the microwave frequency range and EMC applications.