In this paper, radiation at broadside is studied for a general class of leaky-wave antennas (LWAs) comprised grounded slab covered with partially reflecting surface, on the basis simple transverse equivalent network model structure. The analysis one-dimensional (1-D) version such LWA excited by line source shows that central role in establishing features played condition phase and attenuation constants leaky mode responsible are equal. When happens, beam single peak verge splitting into two...

In this paper an investigation is presented of metamaterial structures excited by a line source aimed at producing narrow directive beams. The structure under consideration grounded slab made homogeneous medium with plasma-like dispersive permittivity; for low values the permittivity extremely beam pointing broadside can be obtained. Conditions maximization radiation are given and narrow-beam effect shown to related excitation leaky mode supported slab, corresponding small equal phase...

This review paper summarizes various aspects of directive beaming and explains these in terms leaky waves. Directive occurs antenna design where a narrow beam is obtainable by using fairly simple planar structures excited single source. These include Fabry-Pérot cavity as well metamaterial made from artificial low-permittivity media. also the optical area it has been observed that highly beams can be produced small apertures metal film when an appropriate periodic patterning placed on film....

The piezopotential in floating, homogeneous, quasi-1D piezo-semiconductive nanostructures under axial stress is an anti-symmetric (i.e., odd) function of force. Here, after introducing piezo-nano-devices with floating electrodes for maximum piezo-potential, we show that breaking the nature piezopotential-force relation, instance by using conical nanowires, can lead to better nanogenerators, piezotronic and piezophototronic devices.

Analytical expressions are presented for the intraband conductivity tensor of graphene that includes spatial dispersion arbitrarily wave-vector values and presence a nonzero Fermi energy. The elements derived from semiclassical Boltzmann transport equation under both relaxation-time approximation Bhatnagar-Gross-Krook model (which allows an extra degree freedom to enforce number conservation). based on linear electron near Dirac points, extend previous results assumed small values; these...

Two-dimensional leaky-wave antennas offer effective, compact, single-feeder, easy-to-fabricate solutions to the longstanding problem of realizing a simultaneously directive and low-profile radiating device. These traveling-wave have been thus proposed as wideband, reconfigurable, or frequency-scanning structures in different application contexts, ranging from microwave terahertz frequency range. diverse contexts call for comprehensive guide characterizing designing two-dimensional antennas....

Two-dimensional leaky-wave antennas offer effective, compact, single-feeder, easy-to-fabricate solutions to the longstanding problem of realizing a simultaneously directive and low-profile radiating device. These traveling-wave have been thus proposed as wideband, reconfigurable, or frequency-scanning structures in different application contexts, spacing from microwave terahertz frequency range. diverse contexts call for comprehensive guide characterizing designing two-dimensional antennas....

Radiation at broadside from leaky waves is studied for one-dimensional periodic structures modeled by means of a transmission line periodically loaded series or shunt loads. occurs via an axially fast spatial harmonic in neighborhood the open-stopband frequency; operation such frequency range here approximate asymptotic Bloch analysis adopted equivalent network and simple array-factor calculation radiated far field. The condition equal values phase attenuation constants radiating shown to...

The problem of accelerating the calculation periodic Green's function is addressed here for both 3-D and 2-D free-space configurations. In case, periodicity considered along one axis two, generally skew, axes. A comprehensive review existing methods first presented some extensions are developed. possibility treating case complex phase shifts between unit cells, necessary study modes in structures, also investigated. Comparisons among various acceleration performed, thus providing fundamental...

Tunable THz antennas based on a single unpatterned graphene sheet placed inside grounded dielectric multilayer are studied with the aim of characterizing their performance in terms pattern reconfigurability, directivity, and radiation efficiency.The considered structures belong to class Fabry-Perot cavity (FPC) antennas, whose mechanism relies excitation cylindrical leaky waves an ordinary (i.e., non-plasmonic) sinusoidal transverse modal profile.This allows for achieving efficiencies...

An investigation of planar metamaterial antennas consisting grounded substrates with low and/or high values the electric permittivity magnetic permeability excited by dipole sources is presented. Their performances are characterised in terms their capability to radiate levels power density broadside direction and produce narrow pencil beams pointing at directivity. To achieve a directivity, pair weakly attenuated cylindrical leaky waves along substrate; sufficient conditions established for...

A common approach to perform dispersive analyses of waveguides periodic along one direction is based on the electromagnetic simulation a single spatial period structure. However, resulting equivalent two-port network representation cell may lead inaccurate modal results, since mutual coupling between cells has been neglected. When finite number adjacent are simulated, with aim improving accuracy analysis, spurious solutions introduced; they shown here be related nonuniqueness root-extraction...

Radiation features are studied for a grounded wire-medium slab excited by simple canonical source, i.e., horizontal electric dipole. For the first time, an approximate analysis based on homogenized model wire medium as well rigorous full-wave of actual periodic structure presented. The homogeneous takes into account both anisotropy and spatial dispersion metamaterial in long-wavelength regime. One rather surprising result is that this allows directive pencil beams at broadside azimuthally...

A radially periodic 2-D leaky-wave (LW) antenna is studied for the generation of zeroth-order Bessel beams within a limited spatial region and over wide-frequency range. The design wideband based on an annular metal strip grating placed top grounded dielectric slab, supporting cylindrical leaky wave (CLW) with fast backward harmonic. focusing capabilities relevant LW aperture fields are investigated considered frequency range (15-21 GHz), in conjunction dispersion analysis optimized...

A low-cost leaky-wave antenna using cylindrical surface waves propagating on a grounded dielectric slab is proposed. The excited are then perturbed into regime, by the addition of annular microstrip-based ("bull-eye") gratings. Various surface-wave modes may be considered, however, we desire to achieve radiation from fundamental TM0 mode due its zero cutoff frequency and possibility for efficient excitation. comprehensive design strategy detailed in paper. It based both an accurate knowledge...

In this work, a systematic design of Fabry-Perot cavity antennas based on leaky waves is proposed in the THz range.The use different topologies for synthesis homogenized metasurfaces shows that specific fishnet-like unit-cell particularly suitable efficient radiating devices.Accurate full-wave simulations highlight advantages and disadvantages geometries, thoroughly considering bounds dictated by technological constraints homogenization limit as well.The radiative performance designs...

Different configurations of leaky-wave antennas (LWAs) based on graphene metasurfaces are studied. The electronic properties a metasurface in the low THz range investigated details order to discuss reconfigurability features presented structures. Simple exact formulas for evaluating ohmic losses related surface plasmon polariton (SPP) propagation along suspended sheet, and relevant figures merit SPP propagating over generic given. Such allow us explain efficiency reconfigurable SPPs...

A low-cost compact planar leaky-wave antenna (LWA) is proposed offering directive broadside radiation over a significantly wide bandwidth. The design based on an annular metallic strip grating (MSG) configuration, placed top of dual-layer grounded dielectric substrate. This defines new two-layer parallel-plate open waveguide, whose operational principles are accurately investigated. To assist in our design, method-of-moments dispersion analysis has been developed to characterize the relevant...

A planar substrate-superstrate configuration loaded by a graphene sheet is proposed as novel reconfigurable antenna for terahertz applications. The effects of the introduction on dispersion and radiation properties fundamental leaky modes supported structure are analyzed in detail, with aim investigating possibility beam scanning at fixed frequency varying chemical potential via an electrostatic bias. After optimizing position inside substrate achieving maximum directivity broadside, large...

This paper deals with the analysis of surface waves supported by a metamaterial layer on ground plane, and investigates potentiality these grounded slabs as substrates for planar antennas. Both double- single-negative media, either epsilon- or mu-negative, are considered. As is known, such structures may support two kinds waves, i.e., ordinary (transversely attenuating only in air) evanescent also inside slab) waves. A graphical performed proper real solutions dispersion equation TE TM...

Dispersion properties of the dominant modes supported by different 2-D graphene-based nanowaveguides are studied means an exact approach based on transverse-resonance technique and using equivalent-circuit representation graphene sheets which also takes into account spatially dispersive nature conductivity: it is quantitatively shown that neglecting spatial-dispersion effects can cause errors in determination modal extremely slow surface waves, well below terahertz regime. The features thus...

Focusing light's energy in the near field, beyond diffractive limit, is key to progress fields as diverse microscopy, electronics, telecommunication, wireless power transfer, and ablation tomography medicine. The authors address problem by considering a specific class of partially guided waves, known ``leaky'' waves. Interestingly, only subclass backward leaky waves found be useful here. Qualitative quantitative assessments furnish general design rules, simple but efficient leaky-wave device...

A tutorial overview is presented on the principles of operation, physical modeling, and design procedures for class planar radiators known as Fabry-Perot cavity antennas (FPCAs), with an emphasis their characterization 2D leaky-wave (LWAs). After recalling principal radiative features, alternative electromagnetic (EM) models are discussed, helping us to gain insight into involved radiation mechanisms from different viewpoints. The approach appears particularly useful in this connection; it...