Absorption Peak Controlled Low-Frequency Wideband Flexible FSS Absorber
Kumud Ranjan Jha, Z. A. Pandit Jibran, Satish K. Sharma
Abstract
This article presents an ultrathin absorber for lower microwave frequency applications. The structure is designed using a thin dielectric substrate and a commercially available magnetic sheet superstrate. Due to its low thickness, it is suitable for both planar and conformal applications. For the normal incidence of the electromagnetic wave, the measured reflectivity ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> )≤–10 dB extends from 1.75–3.4 and 1.7–3.36 GHz in the transverse electric (TE) and the transverse magnetic (TM) modes, respectively. All these have been achieved for a total thickness of 0.023λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><sub>L</sub></i> where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ<sub>L</sub></i> is the wavelength corresponding to the lowest operating frequency. Due to the low thickness, the structure has been bent around a cylindrical base. In the conformal design, with the decrease in the curvature radius, in comparison to the planar structure, the bandwidth expansion has been observed. The equivalent circuit model of the structure has also been rigorously analyzed to understand the behavior of the magnetic sheet superstrate and the dielectric substrate. The absorption peaks ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">APs</sub> ) in the operating band have been noticed. At the normal incidence, against the simulated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">APs</sub> of reflectivity magnitude <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \approx $</tex-math></inline-formula> −20 dB, the measured <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">APs</sub> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \approx $</tex-math></inline-formula> −22 dB, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \approx $</tex-math></inline-formula> −30 dB in TE and TM modes, respectively, have been obtained.