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Pattern Search (PS) optimization algorithm has been used for the design of disordered coding metasurfaces with the aim of reducing both monostatic and bistatic Radar Cross Section (RCS) in the 26–40 GHz frequency range. On this basis, high and low phase-state unit-cells have been defined with special attention to the minimization of coupling between the elementary patterns, thus allowing a quasi-constant 180° phase difference over a broad frequency range. Then, finite size metasurfaces have been designed and fabricated using the printed circuit board technological process. Finally, the experimental characterization of various disordered samples leads to −10 dB monostatic RCS reduction over a relative frequency band broader than 35% with a good agreement with both simulated and analytic theoretical predictions. This illustrates the relevance of disordered coded patterns for RCS reduction as well as the PS optimization approach as a design method of coding metasurfaces. [ABSTRACT FROM AUTHOR]

A metasurface consisting of a 2D periodic square lattice of metallic square ring resonators is considered for supporting spoof surface plasmon polariton (SSPP) modes. First, SSPP modes are highlighted by simulated dispersion curves. The dispersion curves are analyzed by considering hybridization of modes in either a patch or an aperture array with frequency shifts. Hybridization of modes is also supported by means of surface current and electric field mappings showing consistent symmetric and anti-symmetric fields. Second, it is shown that a dipole antenna located near the metasurface is able to generate SSPP modes. The transmission spectra between two antennas located at each extremity of the metasurface show transmission enhancements compared with propagation in free space. The transmission enhancements are shown for different locations of the antennas either facing each other or positioned in diagonal. Finally, the transmission enhancement is connected to SSPP modes by comparing the transmission spectra and the measured dispersion curves with each other. Specifically, two transmission windows measured for an embroidered metasurface are related to the cutoff frequency of the two SSPP modes supported by the metasurface as evidenced by the measured dispersion curves. [ABSTRACT FROM AUTHOR]

The absorption mechanisms of Poisson-distributed disordered Metal-Insulator-Metal structures are investigated theoretically and numerically. In particular, from the Poisson point process, Slivnyak–Mecke integrals are used to predict the number of isolated particles and majority clusters as a function of the particle density z. Then, the impact of these numbers on peak, mean, and bandwidth absorbance is calculated by full-wave electromagnetic analysis. It is shown that the peak absorbance reaches a maximum value of higher than 0.9 for a particle density of 0.6 cm−2 originating from main contributions of monomers and dimers whereas trimers represent less than 6% of the total number of particles. The conclusions of these studies are experimentally confirmed by means of free-space characterization. [ABSTRACT FROM AUTHOR]

The properties of disordered metamaterial absorbers are analyzed on the basis of numerical simulations and experimental characterizations. A broadening of the absorption spectrum is clearly evidenced. This effect is the consequence of both the coupling between nearby resonators leading to the occurrence of extended magnetic resonance modes and the interconnection of elementary particles yielding the definition of resonating clusters. The angular robustness of the absorbing structure under oblique incidence is also demonstrated for a wide domain of angles. [ABSTRACT FROM AUTHOR]

This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60°. [ABSTRACT FROM AUTHOR]

We report on the experimental investigation of a non-linear (NL) Co-Planar Waveguide (CPW) fabricated by means of a ferroelectric film. In contrast to conventional NL-CPW, periodically loaded by lumped varactors, the tunable ferroelectric material is fully distributed along the propagation direction and the transmission line does not intrinsically exhibit Bragg cutoff. The experimental demonstration is carried out by means of a 160 nm-thick Pb0.4Sr0.6TiO3 ferroelectric film voltage-controlled via the 1 μm-slot of a CPW transmission line. In a first stage, complex dielectric constant has been retrieved from scattering parameters measurements up to 60 GHz and for a bias voltage ranging from 0 to 30 V. High performances in terms of tunability have been found by a relative permittivity change under 30 V as high as 60% in the overall frequency band. Subsequently, the tunable ferroelectric CPW was used for second and third harmonics generation for a fundamental at centimeter wavelengths. While for low dc-voltage, third harmonic generation is dominant, it is found a main harmonic generation of rank 2 at higher dc bias voltage in agreement with the symmetry properties of the C(V) characteristics. [ABSTRACT FROM AUTHOR]

On the basis of a fishnet-like structure, we analyze a metamaterial design involving dimer aperture arrays. It is shown that this approach leads to very strong Fano resonances within the transmission spectrum. The role of the Wood anomaly in the enhancement of the magnetic field is pointed out in order to explain this transmission characteristic. A sensitivity numerical analysis of this resonant feature is carried out. A figure of merit, defined as the ratio between the sensitivity and the width at half maximum of the resonance, as high as 830, is obtained. To our knowledge, this value is greater than the ones reported so far in literature using the inter-particle electromagnetic induced transparency principle. This property is of great interest for environment control applications, especially for sensing of highly diluted media, such as gaseous phase pollutants, as a complement to conventional spectroscopy techniques. [ABSTRACT FROM AUTHOR]

A split ring resonator (SRR) antenna integrated in textile by embroidery is reported. The antenna was designed and produced by targeting two goals. First, a size reduction of the antenna was achieved by means of an SRR. Secondly, the connection loss was reduced by using a copper wire dipole fixed by embroidery. On the basis of numerical simulations, three operating modes are evidenced depending on the individual resonance frequency either of the dipole or resonator‐related. Especially, a balanced mode is confirmed by experiments with two resonances measured at 1.8 and 2.2 GHz with a return loss greater than 31 dB. Finally, the textile antenna exhibits a radiation pattern similar to the radiation pattern of a dipole antenna. [ABSTRACT FROM AUTHOR]

A ferromagnetic material involving nickel-iron particles embedded in a polyethylene matrix is synthesized and electrically characterized between 1 and 12 GHz. These measurements show the combination of electric and magnetic activity along with significant loss terms. We take benefit of these properties for the design of broadband electromagnetic absorbers. To this aim, we use a fractal structuring based on Moore curves. The advantage of etching patterns over metallic ones is clearly evidenced, and several pattern absorbers identified by their Moore's order iteration are designed and analyzed under oblique incidence. [ABSTRACT FROM AUTHOR]

We report on broadband low-loss properties of Ω-based metamaterials. It is shown that interconnecting elementary current-loops via their arms can yield to a relative bandwidth of around 70% for infinite arrays. Combining interconnected and disconnected sections permits one to engineer the left-handed and right-handed dispersion branches with the prospect of composite artificial media such as those initially proposed by Itoh and coworkers (IEEE Microwave Mag 34 (2004) 34–50) in the context of transmission lines. This typical behavior is interpreted through a lumped element model. At last, some guidelines to optimize the transmission properties of Ω-shaped arrays are presented. These results are discussed on the basis of recently published data concerning Ω-shaped and C-shaped particles. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 84–90, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22034 [ABSTRACT FROM AUTHOR]