Wide-incident-angle, polarization-independent broadband-absorption metastructure without external resistive elements by using a trapezoidal structure

Abstract

The absorption of electromagnetic waves in a broadband frequency range with polarization insensitivity and incidence-angle independence is greatly needed in modern technology applications. Many structures based on metamaterials have been suggested for addressing these requirements; these structures were complex multilayer structures or used special materials or external electric components, such as resistive ones. In this paper, we present a metasurface structure that was fabricated simply by employing the standard printed-circuit-board technique but provides a high absorption above 90% in a broadband frequency range from 12.35 to 14.65 GHz. The metasurface consisted of structural unit cells of 4 symmetric substructures assembled with a metallic bar pattern, which induced broadband absorption by using a planar resistive interaction in the pattern without a real resistive component. The analysis, simulation, and measurement results showed that the metasurface was also polarization insensitive and still maintained an absorption above 90% at incident angles up to 45°. The suggested metasurface plays a role in the fundamental design and can also be used to design absorbers at different frequency ranges. Furthermore, further enhancement of the absorption performance is achieved by improved design and fabrication.

Figure 1

(a) Schematic illustration of the broadband-absorption metasurface, (b) the unit cell, and (c) high absorption in both the TE and TM modes.

Figure 2

(a) Absorption of a single bar of various lengths (L). (b) A single bar with various strip widths (W).

Figure 3

(a) Comparison of the absorption between single and coupled-bars; (b–d) absorption of a coupled-bar with various parameters: length difference (X), strip width (W), and spacing (S), respectively.

Figure 4

Compared absorption of the metasurfaces constructed with single and coupled-bars.

Figure 5

Comparison of the E-field intensity distributions in a unit cell of the structure constructed with (a–c) single- and (d–f) coupled-bars at various frequencies.

Figure 6

Equivalent circuit model of the proposed metasurface.

Figure 7

Experimental setup and the fabricated metasurface.

Figure 8

Comparison between the simulated and measured absorption of the metasurface in TE mode at (a) 0, (b) 15°, (c) 30° and (d) 45°.

Figure 9

Comparison between simulated and measured absorption of the metasurface in the TM mode at (a) 0, (b) 15°, (c) 30°and (d) 45°.