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.

In this article, a single layer co-polarization broadband radar absorber is presented. Under normal incidence, it achieves at least 90% of absorption from 5.6 GHz to 9.1 GHz for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Our contribution and the challenge of this work is to achieve broadband absorption using a very thin single layer dielectric and it is achieved by rotating the resonating element by 45°. An original optimized Underlined U shape has been developed for the resonating element which provides a broadband co-polarization absorption. The structure is 12.7 times thinner than the wavelength at the center frequency. To understand the absorption mechanism, the transmission line model of an absorber and the three near unity absorption peaks at 5.87 GHz, 7.16 GHz and 8.82 GHz have been used to study the electric and magnetic fields. The physical insight of how the three near unity absorption peaks are achieved has also been discussed. After fabricating the structure, the measurements were found to be in good agreement with the simulation results. Furthermore, with the proposed original UUSR resonating element, the operational bandwidth to thickness ratio of 6.43 is obtained making the proposed UUSR very competitive.

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The total scattering cross section (or width) of strongly scattering metallic objects can be reduced by using various cloaks, which are complex structures with a limited frequency bandwidth. In many applications, however, dramatic reduction of total scattering is not always required, for instance, when backscattering reduction is the critical parameter. Moreover, the direction of illumination is sometimes known and scattering reduction for other illumination directions is not required. In these scenarios, it is possible to achieve the desired scattering reduction using much simpler manufactured devices. In this paper, we explore possibilities to reduce backscattering and forward scattering from cylindrical bodies for plane-wave illumination from a certain direction. The proposed scattering-reduction device is a shell formed by several sectors of different uniform dielectric materials. We compare the requirements on the material cover which are needed to reduce backscattering and forward scattering widths and outline the corresponding design approaches. We show that all-dielectric and easily realizable structures can effectively reduce total scattering without using active materials or non-uniform anisotropic materials. We develop and numerically test the method for TE-polarized incident waves, since this polarization is more critical for considered applications.

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