Higher Order Plasma-Based Tunable Absorber Using Magneto-Dielectric Substrates

This paper presents a multilayer absorber based on the technique previously developed for the design of a thickness customizable high-order bandpass frequency selective surface (FSS). Lossy substrates are used to absorb the electromagnetic energy in the FSS backed by a ground plane. Such technique allows simple integration of the tuning elements, while simultaneously providing the design option to realize the absorber with specific/desired thicknesses. The lossy substrates are perforated to host discrete electrically tunable ceramic gas-encapsulating chambers (plasma-shells). These plasma-shells enable dynamic control of the absorption spectral band. To demonstrate the design flexibility and performance, a second order frequency selective absorber operating at the C-band (center frequency at f
₀
= 6 GHz with 17% fractional bandwidth) is designed with different thickness configurations. Then the plasma-shells are strategically integrated in the design in order to control the location of both absorption resonant frequencies by applying different plasma frequencies. Full-wave electromagnetic simulations are carried out to validate the proposed concepts.