Broadband Absorber With High Angular Stability Based on Magnetic Material
Weiliang Yu, Yi Du, Wenlei Wang, Qingquan Tan, Leilei Liu, Guo Qing Luo
Abstract
This communication proposes a broadband absorber that exhibits excellent angular stability. A unit cell is formed by stacking a modified magnetic material layer, an air spacer layer, and a grounded magnetic material layer. An equivalent circuit model (ECM) is established for the absorber, studying the surface impedance and the conditions, in which the absorption rate surpasses 90% at various incidence angles. Furthermore, a prototype is fabricated, assembled, and measured to confirm the operation feasibility of the absorber. The experimental results demonstrate a stable absorption band (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert \le -10$ </tex-math></inline-formula> dB) between 2.4 and 7.3 GHz under normal incidence, with a fractional bandwidth (FBW) of 101% and a relative thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.099\lambda _{L}$ </tex-math></inline-formula>. When the incident angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta $ </tex-math></inline-formula> reaches 60°, the absorption performances remain the same for TE- and TM-polarized oblique incidences. The measured results demonstrate that the absorber attains an absorption rate of over 80% within the ±70° airspace range.