Analysis and Design of Ultra Thin Electromagnetic Absorbers Comprising Resistively Loaded High Impedance Surfaces

Abstract

High-impedance surfaces (HIS) comprising lossy frequency selective surfaces (FSS) are employed to design thin electromagnetic absorbers. The structure, despite its typical resonant behavior, is able to perform a very wideband absorption in a reduced thickness. Losses in the frequency selective surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of a large number of lumped resistors. The effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model. It is shown that the optimum value of surface resistance is affected both by substrate parameters (thickness and permittivity) and by FSS element shape. The equivalent circuit model is then used to introduce the working principles of the narrowband and the wideband absorbing structure and to derive the best-suited element for wideband absorption

Circuit modeling of multiband high-impedance surface absorbers in the microwave regime

“…12,13 More recently, ultrathin absorbers have been introduced, with losses either in the dielectric slab 14 or in the metallic elements of frequency-selective surfaces. 15,16 The common feature of all of the aforementioned absorbing structures is that they operate in a single narrow frequency band with high absorption at a specific frequency (independently of their specific operating frequency regimes). This fact limits their use in applications such as spectroscopic detection and identification of explosives, contaminations, and rare-earth ions, which have distinct absorption features at multiple frequencies.…”

“…For instance, the problem of propagation of electromagnetic waves through wire media, which has been essential for the development of metamaterial science (wire media behave as plasma with negative index of refraction at optical frequencies), was addressed several decades ago by using circuit analogies. 21,22 More recently, circuit models for analyzing HIS absorbers 14,16,23,24 have been proposed with the aim of avoiding the lengthy and cumbersome computations demanded by the numerical simulations. Indeed, problems closely related to the ones treated in this work have been analyzed following the circuit approach presented in Refs.…”

Quasi-Optical Frequency Selective Surface for Atmospheric Remote Sensing Application

“…Unlike FSS arrays which simply consist of freestanding metal apertures or strips, this quasi-optical spatial filter is a substratebased FSS [15,16] with periodic unit cells. This type of FSS can easily be designed to operate at oblique incident angles and band pass modes.…”

Improvement of Microwave Absorbance of Polymer Composites of W-Type Hexaferrite Powders by Attachment of Frequency Selective Surface

“…FSS are planar periodic structures of identical patches or apertures of conducting elements, and are generally employed in front of a grounded dielectric slab (substrate) to synthesize high-impedance absorbing surfaces [8,9]. The behavior of an FSS can be modeled by an equivalent effective resistor-inductor-capacitor (RLC) circuit [10,11]. In such an RLC circuit, the shunted admittance can be represented as a function of R, L, and C, which depend on the electrical resistance and geometry of the FSS [10,12,13].…”

“…The behavior of an FSS can be modeled by an equivalent effective resistor-inductor-capacitor (RLC) circuit [10,11]. In such an RLC circuit, the shunted admittance can be represented as a function of R, L, and C, which depend on the electrical resistance and geometry of the FSS [10,12,13]. Combining an FSS and traditional RAM can produce new impedance matching, and, thereby, result in improvements in microwave absorbance and bandwidth, especially for unmatched RAM.…”