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In this paper, a thin, single layered, wideband, polarization-insensitive, frequency selective surface absorber for radar cross section reduction (RCS) at K U and K bands has been studied analytically and experimentally. The lossy resistive patterns on unit cell is printed using resistive ink and arranged periodically over a low-cost metal-backed FR-4 dielectric substrate. Through appropriate design and optimization, the proposed absorber demonstrates above 90 % absorption for broadband ranging from 15 GHz to 26.6 GHz, with multi-absorption peaks at 15.7, 18.5, and 22.9 GHz. The structure shows a high absorptivity of 96.8 % in the K U band and 95.7 %, and 99.3 % in the K band at the above mentioned frequencies. A fractional bandwidth of 55.8 % has been obtained at the expense of a thickness of 0.0835 λ 1 (λ 1 being the wavelength associated with the lower absorbing frequency). The absorption mechanism has been described with the help of surface current distribution, induced electric field, and equivalent circuit. Further, for both TE and TM waves, analysis of various polarization angles and oblique incidence angles have been investigated. It shows polarization insensitivity to normal incidence and a stable response up to 60° for oblique incidence to TM wave. The proposed absorber's novelty comes through its thin, single-layered structure with wide band response at the K U and K frequency bands via a unique resistive ink pattern on a low cost FR-4. A prototype of the absorber has been fabricated and measured results have been validated with simulated results. A proposed single layered, wideband, thin, polarization, and angular stable absorber using resistive ink is commercially viable for RCS reduction applications at the K U and K band. [ABSTRACT FROM AUTHOR]

In this paper, a polarization-insensitive, metamaterial absorber with more than 91 % absorptivity is investigated numerically and experimentally for radar cross-section reduction at X, Ku, and K bands. The unit cell structure of the absorber is comprised of a symmetrically arranged defective L-shaped patch made of copper metal, which is imprinted on a metal-backed FR-4 lossy dielectric substrate. The proposed absorber yields multiband absorption response at distinct absorption peaks at 11.1, 15.5, and 16.3 GHz along with the broadband response of 4.8 GHz from 18.6 to 23.4 GHz (absorption peaks at 18.9, 20, 21.9, and 23 GHz) in the absorption spectra. The Characteristic mode analysis has been carried out and presented to verify the modes and resonance in the structure. The physical absorption phenomenon is clarified by presenting the induced electric field, top and bottom surface current distribution, and various retrieved constitutive electromagnetic parameters. The structure is studied for various polarization angles for both transverse electric (TE) and transverse magnetic (TM) waves at normal incidence which shows strict insensitivity to the direction of arrival of electromagnetic(EM) signal. The structure is also investigated under oblique incidence for both TE and TM waves where the response holds good up to 50° incident angles in both cases. The novelty of the proposed absorber lies in its multiband response at X, Ku, and K bands through a unique metallic pattern on a thin FR-4 substrate along with characteristics of broadband, polarization insensitiveness, wide incidence angle independence, and compactness incorporated in a single and simple design without using external components. A prototype of the absorber has been fabricated and simulated results are validated with measured results. All the above-mentioned attributes in a simple design make it commercially suitable for radar cross-section (RCS) reduction and energy harvesting applications at X, Ku, and K bands. [ABSTRACT FROM AUTHOR]

This paper focuses on the design and analysis of a polarization-insensitive wide-angle broadband metamaterial absorber for stealth applications at the K band. The unit cell of the metamaterial absorber is comprised of a symmetrically arranged ladder shape geometry made of copper metal, which is imprinted on a metal-backed FR-4 substrate. The structure shows more than 91% absorptivity ranging from 21.2 to 28.2 GHz for both transverse electric (TE) and transverse magnetic (TM) polarized waves under normal incidence. The topology is four-fold symmetric and yields polarization-insensitive responses for different angles of polarization under both TE and TM polarized waves. The structure is also investigated under oblique incidence where the 80% absorptivity holds up to 45° incident angles for both TE and TM waves. The absorption mechanism is explained with the help of top and bottom surface current distribution, induced electric field, and parametric analysis. To verify the resonances in the structure, characteristic mode, and equivalent circuit analysis have been carried out and presented. A prototype of the absorber has been fabricated and simulated results are validated with measured results. The novelty of the proposed absorber lies in its unique metallic pattern on a λ 0 /8 thin FR-4 substrate while showing the wide absorption bandwidth to normal and oblique incidence. All the above-mentioned attributes in a simple design make it commercially suitable for radar cross-section (RCS) reduction applications at the K band. [ABSTRACT FROM AUTHOR]