Abstract

This study focused on the radome and proposed an absorber with a meta-dome structure for ultra-wideband radar absorption using an FR-4 dielectric material on the metasurface absorber for protection. In addition to protecting the absorber, the metasurface absorber exhibited ultra-wideband frequency absorptivity from radar signals, with an absorptivity band from 4.6–12 GHz, including the C and X frequency bands of radar signals. A wide incidence angle should also be considered in addition to the absorption frequency band. Experimental results were obtained for all polarization angles at normal incidence for 5–14 GHz. Sensitivity to incident angle from 0° to 40° in the transverse electric mode and 0° to 60° in the transverse magnetic mode were observed. The proposed concept was demonstrated using full-wave simulation and experimental measurements.

Highlights

  • Radome is a compound word for a radar dome, a device that maintains radar performance and protects the radar from the external environment[1,2]

  • For oblique incidence, absorptivity decreases as the incidence angle increases, due to the wave amplitude reflected from the metasurface absorber varying

  • The metamaterial absorber without dielectric material exhibited more than 90% absorptivity from 7.8–13.9 GHz, which decreased to 7.8–8.5 GHz and 8–9 GHz for transverse electric (TE) and transverse magnetic (TM) mode at 40° incidence, as shown Fig. 6(a,b), respectively

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Summary

Numerical Simulations

The proposed meta-dome consists of a metasurface absorber and a dielectric meta-dome as shown Fig. 2(a). We placed the dielectric meta-dome on the metasurface absorber to protect it and used fire retardant or flame resistant 4 (FR4) substrates (dielectric constant ɛr = 4.4 and loss tangent = 0.02) for the metasurface absorber and meta-dome, as shown Fig. 2(b). Substrate thicknesses t1 = t3 = 2.4 mm, and we employed a fan shaped structure to achieve electromagnetic resonance, as in shown Fig. 2(c). Since the proposed shape was symmetrical, the meta-dome is polarization and angle insensitive. It is impossible to avoid air gaps when the metasurface absorber and dielectric meta-dome are joined, we set an air gap t2 = 0.4 mm. We employed the ANSYS high frequency structure simulator (HFSS) for numerical simulations

Absorptivity can be expressed as
ZM ZM cos θi cos θi
Experimental Verification
Methods
Discussion
Findings
Additional Information
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