Abstract

A thin broadband dual-layer radar absorber based on periodic Frequency Selective Surfaces (FSS) to tackle Electromagnetic Interference (EMI) in radomes is presented in this article. The proposed structure consists of periodically arranged metallic patterns printed on two dielectric substrates separated by an optimized air gap. Under normal incidence, the proposed structure exhibits at least 89.7% of absorption in the whole band of 4.8 GHz to 11.1 GHz for both Transverse Electric (TE) and Magnetic (TM) polarizations. For oblique incidences, a very slight decrease in the bandwidth is observed in the upper frequency band until 30° and the absorption remains very interesting for higher incidences. The structure is λ/7.2 (λ is the wavelength in free space) thin compared to the center frequency (8.2 GHz). In addition, parametric studies have demonstrated that at least 90% of absorption can be produced with our structure by adjusting the thicknesses of the dielectric substrates. Another issue that is presented and discussed in this paper is a new approach for evaluating the performance of absorbers. In fact, studies show that the absorber can compete with other recent broadband absorbers. After fabricating the structure, the measurements were found to be in good agreement with the simulation results.

Highlights

  • Electromagnetic wave absorbers cover a range of applications in defense systems[1] such as reduction of radar cross section, stealth applications, reduction of Electromagnetic Interference (EMI) between electronic equipments and others

  • The absorber is composed of two layers separated with an optimized air gap of thickness, g = 1.5 mm

  • Copper having 5.8 ∗ 107 S/m of electric conductivity and 0.0175 mm of thickness is used for the metallic patterns and ground plane, and dielectric FR4 of relative permittivity ε = 4.2 and loss tangent δ = 0.018 is used for the two dielectric substrates

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Summary

Introduction

Electromagnetic wave absorbers cover a range of applications in defense systems[1] such as reduction of radar cross section, stealth applications, reduction of EMI between electronic equipments and others. In order to enlarge the bandwidth, two of the popular techniques used, consist of incorporating resonating elements working at nearby frequencies by arranging on the same plane[18,19,20,21] or by using multi layers[22,23,24]. Using well customized magnetic materials[25], can decrease the thickness[26] but they can be very expensive For these reasons, designing thin broadband radar absorbers with available dielectrics especially for low frequencies (VHF/UHF) and the gigahertz regime (radio frequency and microwave) is very complicated and is a challenging topic. The designed structure achieves a low profile which can reach thickness value that is very close to the theoretical limit[26] as detailed later in the paper

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