Experimental demonstration of the enhanced transmission through circular and rectangular sub-wavelength apertures using omega-like split-ring resonators

Cataloged from PDF version of article.Enhanced transmission through circular and rectangular sub-wavelength apertures using omega-shaped split-ring resonator is numerically and experimentally demonstrated at microwave frequencies. We report a more than 150,000-fold enhancement through a deep sub-wavelength aperture drilled in a metallic screen. To the authors’ best knowledge, this is the highest experimentally obtained enhancement factor reported in the literature. In the paper, we address also the origins and the physical reasons behind the enhancement results. Moreover, we report on the differences occurring when using circular, rectangular apertures as well as doublesided and single-sided omega-like split ring resonator structures. (C) 2012 Elsevier B.V. All rights reserve

Temporal Rainbow Scattering at Boundary-Induced Time Interfaces

Since the dawn of modern optics and electromagnetics, optical prism is one of the most fascinating optical elements for refracting light. Exploiting its frequency dispersive behaviour, a prism is able to refract different frequencies in different directions, realizing polychromatic light rainbows. Recently, thanks to their engineerable electromagnetic response, metamaterials have been exploited for achieving novel refractive scattering processes, going beyond the classical prism effects. In this Manuscript, we report on a novel rainbow-like scattering process taking place at the interface of a boundary-induced temporal metamaterial realized by instantaneously opening the boundary conditions of a parallel plate waveguide. Changing abruptly the conductivity of one of the two metallic plates, we demonstrate that an equivalent temporal interface between two different media is realized, and the monochromatic wave propagating into the waveguide gets scattered into a polychromatic rainbow in free-space. We derive the relationships between the waveguide mode and the raising rainbow in terms of scattered amplitude and frequencies as a function of the elevation angle with respect to the waveguide axis. We apply the underlying physics to control the temporal rainbow by imposing a principal direction of scattering by design. Full-wave numerical simulations are performed for computing the rainbow temporal scattering and verifying the design guidelines for achieving controlled temporal rainbow scattering.Comment: 14 pages, 3 figures, Appendi

Analytical Model of Connected Bi-Omega: Robust Particle for the Selective Power Transmission Through Sub-Wavelength Apertures

Cataloged from PDF version of article.In this paper, we present a new analytical model of the connected bi-omega structure consisting of two bi-omega particles connected together through their arms. A single bi-omega particle consists of a pair of regular equal omegas with mirror symmetry. Assuming the individual bi-omega particle electrically small, the equivalent circuit is derived, in order to predict its resonant frequency. Then, two bi-omega particles are connected together, obtaining a symmetric structure that supports two fundamental modes, with even and odd symmetries, respectively. The proposed analytical model, then, is used to develop a procedure allowing the design of the particle for a desired resonant frequency. The effectiveness of the proposed analytical model and design guidelines is confirmed by proper comparisons to full-wave numerical and experimental results. We also demonstrate through a proper set of experiments that the resonant frequencies of the connected bi-omega particle depend only on the geometrical and electrical parameters of the omegas and are rather insensitive to the practical scenario where the particle itself is actually used, e.g. in free-space, rectangular waveguide or across an aperture in a metallic screen

Piezoresistive Elastomer Composites Used for Pressure Sensing

Pressure sensors with capability to detect small physical movements and mechanical deformations have been widely used in wearable and medical applications. However, devices that are commercially available currently require complex designs and fabrication and present only a limited force-range sensitivity. To simplify the design, a thermoplastic polyurethane (TPU)/ carbon nanotubes (CNTs) composite film has been developed using a melt extrusion technique followed by compression moulding. Pressure sensors were made from these films, whose piezoresistive response have been analysed as a function of the concentrations of CNTs, around the percolation threshold. The changes in the voltage of the device with applied pressure was continuously measured using a voltage divider system coupled with an electromechanical test machine that dynamically loaded the sensors under compression. The voltage divider system was tuned to obtain the best sensitivity and signal/noise (S/N) ratio for each device tested. The results showed that sensors containing a target of 2.5 wt.% CNTs had market leading sensitivity and repeatability during long-term stability testing and showed high durability during underwater testing indicating that such devices can be used as a promising robust pressure sensitive sensor in wearable devices

Guest Editorial Special Cluster on Functionalized Metasurface-Based Covers and Unconventional Domes for Dynamic Antenna Systems

The papers in this special section focus on recent advancements in this field and provide an overview of the potential applications of this technology in the next generation antenna devices, with emphasis on metamaterial-based enhancements enabling real-time control of their radiation characteristics

Multibeam scanning antenna system based on beamforming metasurface for fast 5G NR initial access

Fifth-generation (and beyond) networks are characterized by ever more demanding requirements in terms of speed, bandwidth, and number of servable users. Fast and reliable access to the main network is mandatory, requiring technologies and procedures that ensure high performing cell search and initial access (IA). Existing phased array antennas (PAAs) are limited by the single beam scanning approach and complex feeding systems. In this paper, a beamforming metasurface that shifts the field manipulation from an electric level to an electromagnetic one is proposed for speeding up the IA procedure with respect to a traditional system using PAAs. The main advantage is given by the simultaneous transmission of multiple signals in different directions. The numerical results demonstrate that a much faster IA with similar success probability can be reached. Our system provides high gain, parallel computation, and scalability for larger systems, becoming a relevant candidate in the new radio and smart electromagnetic environment context

Metasurface dome for above-the-horizon grating lobes reduction in 5G-NR systems

The use of fifth-generation (5G) new radio (NR) spectrum around 26 GHz is currently raising the quest on its compatibility with the well-established Earth exploration-satellite service, which may be blinded by the spurious radiation emitted above the horizon (AtH) by base station (BS) antennas. Indeed, AtH grating lobes are often present during cell scanning due to the large interelement spacing in BS array antennas for achieving higher gains with a reduced number of RF chains. In this letter, we propose an approach based on an electrically thin metasurface-based dome for the reduction of AtH grating lobes in 5G-NR BS antennas. The proposed scanning range shifting approach exploits the natural lower amplitude of the grating lobes when the antenna array scans in an angular region closer to the broadside direction. The grating lobe reduction is here demonstrated considering a 1x4 phased linear antenna array operating under dual-liner +/- 45 degrees-slant polarization. A simple design procedure for designing the metasurface dome is reported, together with the antenna performances, evaluated through a proper set of numerical experiments. It is shown that the grating lobe radiation toward the satellite region is significantly reduced, whereas the overall insertion loss is moderate