The transmission and reflection properties of frequency-selective surfaces (FSSs) are evaluated through a simple and accurate first-order circuit approach The approximate analysis, based on the parallel between real structure and a lumped-LC-network counterpart, is also useful for acquiring physical insights into the working principles of frequency-selective surfaces The first part of the paper describes a technique for computing lumped parameters of the most common frequency-selective-surface elements The L and C parameters representing a given frequency-selective-surface element are derived only one time, at normal incidence, and stored, so as to form a database The second part of the paper deals with the derivation of simple relations allowing the generalization of the stored LC couples in the case where the frequency-selective surface is printed or embedded in arbitrarily thick dielectric slabs, when the incident angle is varied from normal incidence, or if a different periodicity with respect to the reference periodicity is adopted The generalized lumped parameters are included in an equivalent transmission line for computing the response of generic frequency-selective-surface configurations with no additional computational effort The results obtained through the simplified model presented here are verified by a careful comparison with MoM simulations

Efficient Analysis of Frequency-Selective Surfaces by a Simple Equivalent-Circuit Model

Surface scattering antennas provide adjustable radiation fields by adjustably coupling scattering elements along a wave-propagating structure. In some approaches, the scattering elements are patch elements. In some approaches, the scattering elements are made adjustable by disposing an electrically adjustable material, such as a liquid crystal, in proximity to the scattering elements. Methods and systems provide control and adjustment of surface scattering antennas for various applications.

Surface scattering antenna improvements

Metamaterials are being applied to the development and construction of many new devices throughout the electromagnetic spectrum. Limitations posed by the metamaterial operational bandwidth and losses can be effectively mitigated through the incorporation of tunable elements into the metamaterial devices. There are a wide range of approaches that have been advanced in the literature for adding reconfiguration to metamaterial devices all the way from the RF through the optical regimes, but some techniques are useful only for certain wavelength bands. A range of tuning techniques span from active circuit elements introduced into the resonant conductive metamaterial geometries to constituent materials that change electromagnetic properties under specific environmental stimuli. This paper presents a survey of the development of reconfigurable and tunable metamaterial technology as well as of the applications where such capabilities are valuable.

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Reconfigurable and Tunable Metamaterials: A Review of the Theory and Applications

Metasurfaces are thin two-dimensional metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions. For example, metasurfaces have been demonstrated to p ...

/pdf/roadmap-on-metasurfaces-3hqumgmul7.pdf

Roadmap on metasurfaces

The introduction of electromagnetic (EM) media with unique field manipulation properties, collectively labelled as metamaterials, has boosted the interest toward the design, the fabrication, and the testing of artificial materials whose features can be engineered according to the applicative requirements and user objectives. In this framework, the long-term promise of reconfigurable metamaterial theory (i.e., the possibility to change the EM response of a 2-D/3-D material arbitrarily and in real time) has given the designers an extremely wide number of new degrees of freedom for the synthesis of innovative adaptive systems. Moreover, successful experimental validations of reconfigurable metamaterials in the entire EM spectrum from microwaves to optical frequencies have further stimulated academic and industrial interests in developing devices with enhanced performances, efficiency, and robustness. Nevertheless, the exploitation of reconfigurable metamaterials in commercial devices is still an open problem with several challenges from both the theoretical and technological viewpoints. This paper is then aimed at reviewing the latest advances on reconfigurable metamaterial engineering from the methodological perspective also providing a comprehensive and balanced survey on latest concepts, current trends, and envisaged future developments on this active field of research.

Reconfigurable Electromagnetics Through Metamaterials—A Review

A new general equivalent circuit approach for a thin frequency selective structure (FSS) has been proposed. The method exhibits higher accuracy compared with conventional equivalent circuit approaches, is valid for any angle of incidence and for any lattices, provides a better understanding of how a particular FSS structure operates and potentially allows the synthesis of FSS by optimisation of circuit parameters. In addition its performance is much faster than techniques employing rigorous solutions. A theoretical study of the method has been undertaken using ring slot and rectangular slot elements as test elements for the analysis. Very good agreement in comparison with computational electromagnetics (CEM) software and rigorous methods has been obtained.

Equivalent circuit method for analysis and synthesis of frequency selective surfaces

Passive metamaterials suffer from narrow bandwidths and high losses due to limits imposed by causality. Actively loaded metamaterials on the other hand may be designed to overcome these limitations, with the caveat that stability may be difficult to ensure. In this letter, loops with active non-Foster loads, in which resistance, capacitance, and inductance are negative, are arranged in a periodic lattice to form an effective medium with either negative-Re μ or μ-near-zero magnetic properties over a broad range of frequencies. The stability and effective magnetic properties are examined analytically, as well as with numerical simulations. Furthermore, the tradeoffs between stability, bandwidth, and the lower bounds of the permeability are detailed.

Stability of active magnetoinductive metamaterials

A new modal decomposition equivalent circuit method has been proposed for an analysis of multi-frequency and multi-layer frequency selective structure (FSS). The present paper is an extension of the previously published work where it has been shown that the method is valid for ‘thin’ and ‘thick’ FSS both for angles of incidence up to 60° and for any lattices and potentially allows the synthesis of FSS by the optimisation of circuit parameters. Further investigation has shown the methods validity for the analysis of complex FSS geometries. The method has been successfully applied for the analysis of double-ring slot FSS, ‘A-sandwich’ structures and so on. A very good agreement in comparison with the computational electromagnetic software and rigorous methods such as a periodic method of moments has been obtained.

Multi-frequency and multi-layer frequency selective surface analysis using modal decomposition equivalent circuit method

This paper examines the global social, economic and political changes which are giving rise to an increased demand for mobile satellite communications. It also outlines the investment in new satellite infrastructure and the accompanying technological innovations in terminal antenna systems that are being made to realise high availability broadband for applications as diverse as defence, security, disaster response, and mobile broadband for airborne and maritime applications.

Next generation mobile SATCOM terminal antennas for a transformed world

A device for controlling electromagnetic radiation emitted by a structure is described. The device has a reactive element comprising an array of conductors disposed on a dielectric surface such that the displacement between a conductor and any other conductor adjacent to it is small compared to the wavelength of the electromagnetic radiation. As such, the array of conductors represents an effectively continuous conductive surface to the electromagnetic radiation and the surface impedance of the conductive surface (2) is reactive.

Javier Vazquez

Papers

Equivalent circuit method for analysis and synthesis of frequency selective surfaces

Stability of active magnetoinductive metamaterials

Multi-frequency and multi-layer frequency selective surface analysis using modal decomposition equivalent circuit method

Next generation mobile SATCOM terminal antennas for a transformed world

Radiation controller including reactive elements on a dielectric surface