Low-Profile Plasma-based Tunable Absorber

This paper presents a low-profile tunable absorber based on the interaction between electromagnetic (EM) waves and plasma medium in the microwave regime. The design is implemented by integrating discrete plasma-shells and practical biasing network layers in a resistively loaded frequency selective surface (FSS). Two approaches., comprised of lossy inductive and lossy capacitive FSS layer, are investigated. A transmission line model is used to provide the working principle of the absorption and its frequency tuning capability. The total thickness is about 3.5 mm corresponding to 0.11λ
₀
where λ0 is the free space wavelength of the absorption center frequency (fo =9.5 GHz). Through proper activation of the plasma, which induces a dielectric loading on the FSS layer, a linear tuning response is obtained.