Guidelines for the Design of Ultra-thin Microwave Absorbers

This paper discusses some guidelines on the design of ultra-thin (metamaterial) absorbers that operate in the microwave frequency range. The absorber configuration is constrained to the periodic metallic structure (patches) over a grounded dielectric with a thickness less than a tenth of wavelength. Parameters such as patch geometry, distance between patches (gap), thickness, permittivity, and loss tangent of the dielectric substrate are analyzed and their influences on the reflection property of the absorbers are discussed. It is shown that the patch geometry is not the only parameter that should be optimized. Under certain circumstances, other parameters like the gap and the loss tangent are more critical. Some examples are provided to illustrate this situation. Based on these guidelines ultra-thin absorbers having low reflection (smaller than -10 dB) can be designed in a fast and easy manner.