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A wideband conformal microstrip patch antenna suitable for airborne applications is proposed. Dumbbell shaped slots located symmetrically at suitable fraction of wavelength distance from the centre of the patch and a partially cut ground plane is utilised to enhance the operating bandwidth of the patch antenna as compared to the standard conventional patch. Fractional impedance bandwidth (S11<-10 dB) of about 86% with operating range 1.14 GHz to 2.87 GHz for the proposed planar and 81% bandwidth within frequency range 1.16 GHz to 2.74 GHz for the cylindrical antenna configuration (covering S and L bands) is obtained. The antenna shows satisfactory gain in both E and H planes within the operating frequency range. The radius of curvature has been taken electrically small (1.25?) to clearly illustrate the effect of curvature on the performance characteristics of the antenna. [ABSTRACT FROM AUTHOR]

We have simulated the transport properties of a uniformly charged flexible polymer chain and its counterions confined inside cylindrical nanopores under an external electric field. The hydrodynamic interaction is treated by describing the solvent molecules explicitly with the multiparticle collision dynamics method. The chain consisting of charged monomers and the counterions interact electrostatically with themselves and with the external electric field. We find rich behavior of the counterions around the polymer under confinement in the presence of the external electric field. The mobility of the counterions is heterogeneous depending on their location relative to the polymer. The adsorption isotherm of the counterions on the polymer depends nonlinearly on the electric field. As a result, the effective charge of the polymer exhibits a sigmoidal dependence on the electric field. This in turn leads to a nascent nonlinearity in the chain stretching and electrophoretic mobility of the polymer in terms of their dependence on the electric field. The product of the electric field and the effective polymer charge is found to be the key variable to unify our simulation data for various polymer lengths. Chain extension and the electrophoretic mobility show sigmoidal dependence on the electric field, with crossovers from the linear response regime to the nonlinear regime and then to the saturation regime. The mobility of adsorbed counterions is nonmonotonic with the electric field. For weaker and moderate fields, the adsorbed counterions move with the polymer and at higher fields they move opposite to the polymer's direction. We find that the effective charge and the mobility of the polymer decrease with a decrease in the pore radius. [ABSTRACT FROM AUTHOR]

Bright, room‐temperature stable, on‐demand, and highly directional light sources are essential for quantum optical technologies. A design methodology to enhance the emission and collection efficiencies for given collection optics is proposed and demonstrated. Hyperbolic metamaterials (HMMs) offer manipulation of local density of states to improve the emission as well as coupling of emission to high‐K modes. However, metallic losses limit the efficiencies achieved. The HMM structure designed for large, broadband Purcell enhancement with limited metallic losses as well as HMM and antenna design to optimize the collection efficiency is presented. 200 times emission enhancement is reported from CdSeS/ZnS core/shell alloyed quantum dots embedded in a planar HMM structure with cylindrical silver (Ag) patch antenna on the top. 40% collection efficiency is demonstrated for a lens with a numerical aperture of 0.9 and the emission enhancement is about an order of magnitude higher than the previous reports. [ABSTRACT FROM AUTHOR]

Results demonstrating the field effect modulation of ionic transport through an array of cylindrical nanopores fabricated in silicon-on-insulator substrates are presented. Pronounced modulation of the conductance is observed at low electrolyte concentrations when the electric double layers within the nanopores are overlapping. A numerical model based on Brownian dynamics reproduces the measured data. [ABSTRACT FROM AUTHOR]

A toroidal harmonic expansion is developed which is used to represent the vector potential due to a circular cylindrical antenna with a rectangular cross section at any arbitrary point in space. The singular part of the antenna kernel is represented by an associated toroidal harmonic expansion and the analytic part of the kernel is represented by a binomial expansion. A simple example is given to illustrate the application of the toroidal expansion. [ABSTRACT FROM AUTHOR]

The previously proposed near‐field holographic imaging algorithms are based on the data collected over rectangular apertures. In this letter, we propose an approach for three‐dimensional near‐field holographic imaging with data collected over cylindrical apertures. Circular deconvolution is employed to deal with the periodicity of the functions along the azimuthal direction. [ABSTRACT FROM AUTHOR]

In present work a wide band and high gain cylindrical dielectric resonator antenna working in X-band has been designed and validated experimentally. First the bandwidth of the antenna has been enhanced by placing the thin dielectric layer between antenna and feed network. Next gain of the antenna has been increased by placing a layer of high dielectric material at nearly λ/2 distance as superstrate. The proposed design with impedance bandwidth of 3 GHz and gain nearly 11dBi could be used in satellite communication and other wideband wireless applications operating in X-band. [ABSTRACT FROM AUTHOR]

The paper presents a method of construction of cylindrical and azimuthal equalarea map projections of a triaxial ellipsoid. Equations of a triaxial ellipsoid are a function of reduced coordinates and functions of projections are expressed with use of the normal elliptic integral of the second kind and Jacobian elliptic functions. This solution allows us to use standard methods of solving such integrals and functions. The article also presents functions for the calculation of distortion. The maps illustrate the basic properties of developed map projections. Distortion of areas and lengths are presented on isograms and by Tissot's indicatrixes with garticules of reduced coordinates. In this paper the author continues his considerations of the application of reduced coordinates to the construction of map projections for equidistant map projections. The developed method can be used in planetary cartography for mapping irregular objects, for which tri-axial ellipsoids have been accepted as reference surfaces. It can also be used to calculate the surface areas of regions located on these objects. The calculations were carried out for a tri-axial ellipsoid with semi-axes a = 267:5 m, b = 147 m, c = 104:5 m accepted as a reference ellipsoid for the Itokawa asteroid. [ABSTRACT FROM AUTHOR]

This article presents the design and analysis of conformal circular monopole antenna with split ring resonator to get frequency notch characteristics in the wideband. Split ring resonators placed on one side of the substrate and complementary split ring resonators placed on the other side of the substrate at defected ground structure, which yields the frequency notch characteristics with respect to the microstrip feeding. Dual notch band characteristics are obtained between 4-4.3 and 7.3-8.1 GHz. The analyzed conformal characteristic of the antenna supports excellent constant reflection coefficient characteristics over the band at different angles. The impedance and radiation characteristics of the antenna model is analysed in simulation along with unit cell analysis of the SRR and the measured results are providing good agreement with them. [ABSTRACT FROM AUTHOR]

Metasurfaces that manipulate electromagnetic waves have gained significant attention in recent years. The focus has primarily been on planar devices, while many applications require curved surfaces. In this study, the authors propose an analysis approach for cylindrical cascaded (multilayer) metasurfaces. The approach combines the concept of sheet impedance in the spectral domain with a new transmission matrix formulation that is applicable to stratified, canonical curved geometries. Approximate formulas for the sheet impedance of common planar, metallic patterns are also adapted to curved geometries. The reported analysis approach allows one to determine the optimal spectral-domain, azimuthal dependence of a sheet impedance, as well as the best geometrical elements to obtain the required azimuthal variation. The results are verified through several cylindrical metsurface examples. [ABSTRACT FROM AUTHOR]

The dynamics of formation of streamers in a “needle-plane” gap filled with air at atmospheric pressure has been studied. It has been shown that the time dependence of the dynamic displacement current measured by either a current shunt or a collector placed behind a grid electrode is determined by the rate of variation of the shape and dimensions of a streamer. The presence of a single peak on oscillograms of the dynamic displacement current means that a ball streamer is formed in the gap and does not cross the gap during the time of voltage application. The presence of two peaks on oscillograms of the dynamic displacement current means that the ball streamer crosses the gap and reaches the opposite electrode. In this case, the ball streamer is usually transformed to a cylindrical one. It has been shown that the measurement of the dynamic displacement current makes it possible to determine the time dependence of the electric field strength near the planar electrode. [ABSTRACT FROM AUTHOR]

A microstrip patch antenna can be readily installed on any non-planar surface due to its conformal property, and this feature enhances its applicability in many areas. Moreover, in some specific applications, it is desirable and mandatory to provide protection of antenna from the unfriendly surroundings. Therefore, the present work focuses on the antenna with a dielectric cover and analyzes its effect on directivity, gain, and bandwidth at various superstrate air gaps. Two antenna models of single and dual elements are considered here separately, and both are conformal to the cylindrical surface. The antenna parameters are studied under varying superstrate gaps with equal intervals up to a quarter wavelength under fixed cylindrical curvature. It is noted that there is a significant improvement of 6% and 12% in bandwidth at quarter wavelength gap as compared to simple single and dual antenna models without dielectric loading, respectively. Also, both the calculated and measured results show the other important constructive effect of superstrate on the antenna performance. [ABSTRACT FROM AUTHOR]

In static scenarios, binaural sound localization is fundamentally limited by front-back ambiguity and distance non-observability. Over the past few years, “active” schemes have been shown to overcome these shortcomings, by combining spatial binaural cues with the motor commands of the sensor. In this context, given a Gaussian prior on the relative position to a source, this paper determines an admissible motion of a binaural head which leads, on average, to the one-step-ahead most informative audio-motor localization. To this aim, a constrained optimization problem is set up, which consists in maximizing the entropy of the next predicted measurement probability density function over a cylindric admissible set. The method is appraised through geometrical arguments, and validated in simulations and on real-life robotic experiments. [ABSTRACT FROM AUTHOR]

In scattering experiments, incident fields are usually produced by aperture antennas or lasers. Nevertheless, incident plane waves are usually preferred to simplify theoretical analysis. The aim of this paper is the analysis of the electromagnetic scattering from a perfectly electrically conducting polygonal cross-section cylinder when a Gaussian beam impinges upon it. Assuming TM/TE incidence with respect to the cylinder axis, the problem is formulated as electric/magnetic field integral equation in the spectral domain, respectively. The Method of analytical preconditioning is applied in order to guarantee the convergence of the discretization scheme. Moreover, fast convergence is achieved in terms of both computation time and storage requirements by choosing expansion functions reconstructing the behaviour of the fields on the wedges with a closed-form spectral domain counterpart and by means of an analytical asymptotic acceleration technique. [ABSTRACT FROM AUTHOR]

The deflagration-to-detonation transition in hydrogen-air mixtures that fill spiral channels has been studied. A spiral channel has been produced in a cylindrical detonation tube with a twisted ribbon inside. The gas mixture has been ignited by means of a spark gap switch. The predetonation distance versus the twisted ribbon configuration and molar ratio between the gas mixture components has been determined. A pulling force exerted by the detonation tube after a single event of hydrogen-air mixture burnout has been found for four configurations of the twisted ribbon. Conditions under which the use of a spiral tube can be more effective (increase the pulling force) have been formulated. [ABSTRACT FROM AUTHOR]

This letter presents a circularly polarized cylindrical dielectric resonator antenna (DRA) with wide band characteristics. The circular polarization (CP) is actualized by placing a set of symmetric tapered sheets on either side of the feed line, which is quite first time in DRA. The measured results shows 4.0% axial-ratio (AR) bandwidth for AR < 3 dB, while operating over S11 < −10 dB bandwidth of 16.77% (7.1-8.4) GHz with a peak gain of 5.92 dBi. This proposed low profile compact DRA can be a favorable candidate for X-band applications. [ABSTRACT FROM AUTHOR]

In this article, a cylindrical dielectric resonator antenna (CDRA) excited by a 45° rotated square ring slot with a T-shaped coupling microstrip line is investigated for circularly polarized (CP) operation. The proposed antenna shows the dual band characteristics and the lower band is generated due to T-Shaped microstrip line and upper band is due to CDRA. In the proposed antenna, the two degenerate broadside orthogonal modes ( [ABSTRACT FROM AUTHOR]

A significantly feasible high-gain cylindrical dielectric resonator antenna with wideband characteristics is investigated. A simple microstrip-fed slot coupling technique is adopted for excitation of the cylindrical resonator, which is placed over a square slot made at the centre of the ground plane. The upper side of the dielectric resonator is kept open for interference free radiation. To reduce the unnecessary back radiation, the bottom side of the ground plane substrate is covered by a single side copper coated dielectric reflector (1.35λ0 × 1.35λ0 × 0.04λ0) at a small air-gap distance of 4 mm. This helps in abrupt gain enhancement of 101.48% over 17.14% impedance bandwidth. The effect of the reflector on bandwidth, gain and radiation pattern is studied. For validation purpose, a prototype is fabricated and characterised. The measured peak gains are found to be 10.84 and 10.45 dB while resonating at 7.3 and 8.08 GHz, respectively, which are in good agreement with their simulated counterparts. [ABSTRACT FROM AUTHOR]

This letter presents a new technique to fabricate aperture type cylindrical frequency selective surface (FSS) with circular, tripole, and plus shaped element. The cylindrical FSSs exhibit band pass property from 5 to 9 GHz, 11.75 to 14.75 GHz, and 7 to 14 GHz, respectively. A novel method with aluminium foil paper is suggested for fabrication. Cylindrical FSS is fabricated with this technique in laboratory with commercially available aluminium foil paper and is measured practically. In this technique, with the help of laser cutting machine 0.01 mm precision label can be achieved. Both simulated and measured results are in good agreement. The aluminium foil paper made FSS proved to be very light weight, flexible and low cost. [ABSTRACT FROM AUTHOR]

This paper presents the results of using a sensor-integrated workpiece for in situ measurement of strain during an outer-diameter cylindrical grinding process. The motivation of this work is to measure in situ process parameters using integrated sensors in a workpiece in order to characterize the manufacturing process. Resistive sensors that operate on the same principle as conventional strain gauges were fabricated on wafers made of steel using standard microtechnology and later the wafers were diced to form unique sensor-integrated steel components (sensor inlays). These inlays are embedded into a groove on the top surface of a cylindrical workpiece using epoxy adhesive. The workpiece is also made of the same steel as the sensor wafers and has similar properties due to a heat treatment process, thereby maintaining the homogeneity of the material over the whole contact area. The sensor-integrated workpiece was used to perform experiments in a Studer S41 highperformance cylindrical grinding machine. The sensor response to the internal strain was recorded during every grinding step starting from a depth of 1mm down to 2mm from the top surface. Such an application of sensor integration in materials for in situ process monitoring can be used in other manufacturing processes as well and this can help to observe internal loads (mechanical or thermal) in manufacturing processes. [ABSTRACT FROM AUTHOR]

Terahertz absorption in cylindrical quantum well wire under the influence of unsymmetrical electric field is investigated. The two dimensional Schrödinger equation is solved using finite difference method to obtain the eigen states and energies. The absorption spectrum is calculated using the density matrix approach. Results reveal that the absorption peaks are in the terahertz range for specific values of physical parameters. Also the results show that the frequency and amplitude of the absorption peak are completely tunable by changing the electric field and the wire diameter. [ABSTRACT FROM AUTHOR]

A wideband and unidirectional loop antenna with enhanced and stable gain is presented. To reduce the size of the antenna, the loop is loaded with three mu-negative (MNG) metamaterial unit-cells. The proposed unit-cells consist of a series-gap capacitor and a shunt meandered floating inductor. The series capacitive loading is used to excite the zeroth order resonance (ZOR) of the MNG unit-cell, whereas the floating inductor is used to improve impedance matching. To enhance the front-to-back-ratio (FBR) of the antenna and widen its operating bandwidth, the loop is loaded with a tuning slot in the vicinity of the loaded unit-cells. To overcome the low gain of the antenna at frequencies above the ZOR and thus obtain a stable gain, two tightly coupled dumbbell and arc-shaped directors are proposed. The shape and operation of these directors are inspired by the cylindrical capacitor, which achieves higher coupling compared to a planar capacitor with the same area. The antenna achieves a compact size of 0.25\lambda 0 \times 0.29\lambda 0 with a wide fractional bandwidth of 34% at 0.76–1.07 GHz, and peak measured gain and FBR values of 4.5 dBi and 16 dB, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, we present a set of novel and stable formulations to calculate the response of logging tools with horizontal-coil antennas in an eccentric borehole straddling cylindrically multilayered formations. It can be applied in fast forward computation and the inverse problem for electromagnetic (EM) well-logging in deviated and horizontal wells, where eccentric scenarios are often encountered. Our formulations are different from previous ones in following aspects. First, the tool mandrel can be cylindrically multilayered and the electrical parameters of each layer are arbitrary. Namely, it is not limited to being perfectly metallic. Second, the EM propagation in inhomogeneous medium is considered by the generalized reflection and transmission method, in place of the transfer matrices. The associated generalized reflection and transmission coefficients are expressed by the ratios of Bessel or Hankel functions that obviate the notorious overflow problem for numerical computation. Finally, a set of linear matrix functions are constructed to solve for the EM waves in a borehole based on the concept of the generalized reflection, rather than that of the fictitious boundary. Numerical results in comparison with those from other approaches have demonstrated the validity and stability of our new formulations. [ABSTRACT FROM PUBLISHER]

This paper presents a theoretical model of a cylindrical hybrid resonator antenna. The hybrid resonator consists of an annular ring ferrite and a cylindrical dielectric with a dc magnetic bias field, applied in direction parallel to the antenna height. The HE11\delta mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. To validate the proposed approximate analysis, an experimental investigation of an antenna loaded with a biased ferrite is also presented. The presented theory is shown to demonstrate the measured results. The antenna is found to be used as frequency, bandwidth, and polarization tunable antenna. The operating frequency can be chosen in the range from 9.07 to 9.84 GHz. In addition, the bandwidth can be extended from 7.3% to 12.7%. The polarization can be switched from linear to circular. The features mentioned earlier can be achieved by applying the appropriate magnetic field due to the \mathbf HE\mathbf {11\delta } mode splitting behavior. The theoretical model, the design process, and the measured results are presented in detail. The antenna is also found to be capable of tuning the operating frequency as well as the frequency tuning range without changing the overall size of the resonator. [ABSTRACT FROM AUTHOR]

This paper describes an automatic inspection system for detecting defects on the cylindrical surface of lens holders using machine vision. The system is composed of a charge coupled device, a coaxial light and a motor unit. A sequence of partial surface images of a lens holder is grabbed and is reconstructed into a two-dimensional unwrapped image. Then, a series of image processes is used to normalise, segment and detect the defects. Freedom of orientation is one of the advantages of the system, since it permits users to place a to-be-inspected lens holder on the fixture at an arbitrary orientation. Furthermore, a novel global image restoration scheme, based on randomised singular value decomposition, is proposed in this study, in order to quickly detect defects embedded in the high-resolution surface. [ABSTRACT FROM AUTHOR]

One of the major drawbacks of the original Yee’s algorithm is “staircasing.” In an attempt to overcome this flaw, especially when trying to solve electromagnetic problems involving cylindrical geometries, an FDTD scheme was formulated in cylindrical coordinates. The vast majority of works published describe an algorithm with a (2, 2) order of accuracy. In this work, we use a recently introduced methodology, that of constructing finite difference schemes in the spectral domain, combined with the well-established one known as the “modified equation” to analyze existing cylindrical FDTD schemes and synthesize new nonstandard and high-order ones. [ABSTRACT FROM AUTHOR]

In this study, cylindrical dielectric barrier discharge plasma was used to study the catalytic effect on chemical methods of silver nano-particles for the first time. In this method, the processing time is short and the temperature of reaction is low. Also, the reactor is very simple, inexpensive, and accessible. In this work, pure AgNO3 as the precursor agent and poly vinyl pyrrolidone as the macromolecular surfactant were dissolved in ethanol as the solvent. UV-Vis and XRD were used to identify the colloidal and powder nano-particles, respectively. Optical emission spectroscopy was also used to identify the active species in plasma. Effects of gas flow rate, voltage, volume of solution, and processing time were also studied. Moreover, TEM and SEM images presented the mean diameter of nano-particle size around 10 to 20 nm. The results have been very promising. [ABSTRACT FROM AUTHOR]

ABSTRACT An omni-directional antenna in multiple input multiple output (MIMO) arrangement is presented that covers S-band (2.3-2.5 GHz) and C-band (4.4-5.1 GHz) wireless communication applications. One pair of modified PIFA-like radiating structures is used for each of the two bands. These elements are placed on a cylindrical ground plane with bents which is cut from a cylindrical conducting surface to accommodate a device which has a unique shape. Simulated and measured MIMO parameters such as the total active reflection coefficient (TARC), envelope correlation coefficient (ECC), mean effective gain (MEG), and channel capacity loss ( Closs) are computed and presented. Performance results are very satisfactory for a MIMO antenna. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2137-2143, 2016 [ABSTRACT FROM AUTHOR]

A high-gain mushroom-shaped dielectric resonator (DR) antenna for wideband wireless applications, featuring 65% fractional bandwidth, is proposed. The antenna consists of a low-permittivity hollow cylindrical DR provided with a top-mount spherical cap lens and a metal reflector, excited by means of coaxial probes. Suitable shaping of lens and reflector yields high gain (exceeding 14 dBi) and limited back radiation. The proposed antenna features a broadside radiation diagram with stable radiation patterns and wideband impedance matching. Its potential applications include access points for indoor/outdoor wireless multimedia systems as well as satellite terminal receivers. CST Microwave Studio, implementing a full-wave locally conformal finite integration technique, is employed to design and characterize the antenna, while the singularity expansion method is adopted to express the antenna response to arbitrary excitation waveforms. The numerical results concerning the antenna parameters are found to be in good agreement with the experimental measurements performed on an antenna prototype. [ABSTRACT FROM AUTHOR]

This paper presents a new perspective on the analysis of the cylindrical antenna theory. It applies the cylindrical surface waves on an infinitely long cylindrical conductor, which are similar to the Sommerfeld axial cylindrical surface waves, to describe the conventional postulate of applying a sinusoidal current distribution on a cylindrical dipole antenna. This treatment leads to the derivation of simple expression for the current on a cylindrical dipole antenna of finite conductivity, which is in good agreement with the current obtained from the three-term approximations. Also, it proposes an expression for the current on an infinitely long cylindrical dipole antenna of finite conductivity, which is also in good agreement to the current found from applying the Fourier transform technique. Moreover, this paper shows that the complex propagation constant used in the three-term approximation is similar to the complex propagation constant of the principal Sommerfeld wave on the surface of an infinitely long cylindrical conductor. Therefore, a more accurate representation of the current near the feeding point is proposed based on the complex propagation constants of multiple Sommerfeld waves. [ABSTRACT FROM AUTHOR]

At the Kielce University of Technology, a new method of waviness measurement of cylindrical surfaces has been developed. The article deals with the research conducted to find the optimal V-block method parameters that can be used in a measuring device applied to waviness measurement of cylindrical surfaces. In order to keep high measuring accuracy of V-block method, all detectability coefficients which are function of V-block method parameters should not be negative. For this purpose computations were carried out in order to find such angular parameters that can be easily applied in measuring device and allow for obtaining positive detectability coefficients. Results of the study presented in this paper make it possible to modify the design of the measuring device. According to the authors, it will result in increasing the accuracy of V-block waviness measurement of cylindrical parts. [ABSTRACT FROM AUTHOR]

This paper deals with a method to estimate the surface flashover voltage of an insulator in vacuum, in which the distribution of surface charge accumulated due to a secondary electron emission avalanche (SEEA) is taken into account. We show experimental and calculated results for a cylindrical insulator made of ceramic, glass or polymer, where each insulator ranges up to 50 mm in length. Since the surface roughness of specimens affects the progression of SEEA, its influence on the flashover voltage is also examined. The calculation results have demonstrated good agreement with experimental ones except for a case in which the SEEA charge is substantially lowered. For further confirmation of the validity and applicability of our estimation method, we have examined the flashover characteristic of a specimen when its surface consists of smooth and rough regions. The calculation result of this case also agreed with the experimental one. To explain the disagreement that appears in the less charged case, we discuss and propose two flashover mechanisms, including one based on SEEA. [ABSTRACT FROM PUBLISHER]

We propose a method for calculation of the charge distribution along a short (on the wavelength scale) cylindrical antenna in an anisotropic medium and the impedance of the antenna. The method is based on the solution of the corresponding integral equation by using a 'thin' antenna approximation for different angles of antenna orientation relative to the anisotropy axes of the medium. The calculation results coincide with the results obtained earlier by other methods if the antenna axis is not too close to the direction of the asymptote of an open wave-vector surface. The case where the antenna is oriented along this asymptote, in the vicinity of which the angular dependence of the real and imaginary parts of the impedance changes abruptly, is considered in detail. [ABSTRACT FROM AUTHOR]

Millimeter-wave (MMW) imaging techniques have been used for the detection of concealed weapons and contraband carried by personnel. However, the future application of the new technology may be limited by its large number of antennas. In order to reduce the complexity of the hardware, a novel MMW imaging method based on compressive sensing (CS) is proposed in this paper. The MMW images can be reconstructed from the significantly undersampled backscattered data via the CS approach. Thus the number of antennas and the cost of system can be further reduced than those based on the traditional imaging methods that obey the Nyquist sampling theorem. The effectiveness of the proposed method is validated by numerical simulations as well as by real measured data of objects. [ABSTRACT FROM AUTHOR]

Electromagnetic scattering of a single-layer periodic composite panel is investigated. The panel is reinforced by a periodic array of infinite circular cylindrical fibers. A planar wave illuminates the panel with its wave vector orientated obliquely versus the fiber’s axes. In this 2.5-D scattering case, full-wave field representation from multipole and plane-wave expansions yield reflection and transmission coefficients of the longitudinal field components, which is achieved by mode matching at the boundaries. Power reflection and transmission coefficients are obtained from time-averaged Poynting vectors. The work is a prerequisite for modeling electromagnetic nondestructive testing of composite panels, approaching a multilayered structure made by stacking periodic slabs one over the other being the next step. [ABSTRACT FROM PUBLISHER]

A computer-aided technique is proposed to obtain the embedded characteristics of the elements in a cylindrical phased array using a unitcell approach in Ansys High Frequency Structure Simulator (HFSS). The proposed technique is general and can be used with other commercially available electromagnetic (EM) products that support periodic boundary conditions. Therefore, it can be widely adopted by engineers and researchers to analyze arbitrary element structures in cylindrical phased arrays. The implementation of the technique is discussed in detail, and the related formulation is presented. The method is verified by comparing its results with published literature as well as results obtained through full-wave analysis of a ring of microstrip patch antennas in HFSS. [ABSTRACT FROM AUTHOR]

The fundamental limitation (lower bound) on the quality factor (Q) of an electrically small antenna that fully occupies a spherical volume is defined by the well-known Chu limit. More recently, the subject of lower bounds for small antennas of arbitrarily shaped volumes has been given considerable attention in the literature. Gustafsson et al. were the first to present lower bounds for the Q of antennas of arbitrary volume. More significantly, they presented details on the optimum aspect ratios for minimizing the Q of electrically small antennas that fully occupy cylindrical volumes and planar areas. In previous works, we have described several electrically small-wire antenna designs that fully occupy spherical and cylindrical volumes and that are impedance matched and efficient and exhibit Qs that most closely approach the Chu limit and the Gustafsson limit, respectively. [ABSTRACT FROM AUTHOR]

A stepped cylindrical antenna with a higher-order mode ring patch for wideband conical radiation pattern is proposed. To accomplish a low profile with wideband conical radiation characteristics, a stepped cylindrical monopole and a TM41 higher-order mode ring patch with four shorting pins are utilized. The proposed antenna has a monopole-like radiation pattern with a wide 10-dB return loss bandwidth of 11 GHz (2 GHz–13 GHz). It can cover various wireless services, such as wireless broadband (WiBro; 2.3 GHz–2.39 GHz), wireless local area networks (WLAN; 2.4 GHz–2.484 GHz, 5.15 GHz–5.35 GHz, and 5.725 GHz–5.875 GHz), digital multimedia broadcasting (DMB; 2.63 GHz–2.655 GHz), and ultra wideband (UWB; 3.1 GHz–10.6 GHz). The antenna has a height of only 0.12λ0 at 2 GHz. [ABSTRACT FROM AUTHOR]

This paper experimentally and numerically investigates the axial decay of end effects in a cylindrical waveguide under transient loading. End effects, which are defined as an edge response deviating from that of the far field response, are analyzed by applying waves with different spatial distribution on the edge of a waveguide. Four impactors having the same cross-sectional area but different head shapes are impinged upon a long cylindrical waveguide. Surface strains at different locations along the waveguide are recorded and compared. Results from both the experimental and numerical studies indicate that the far field response is not sensitive to the spatial distribution of the applied transient loading. The typical distance beyond which the end effects could be ignored is estimated to be about 2.2 times of the bar radius. These results provide evidence on the existence of dynamic version of Saint-Venant's principle in cylindrical waveguides in high frequency regime. [ABSTRACT FROM AUTHOR]

A composite aperture has been conceived to excite cylindrical dielectric resonator antenna (CDRA) simultaneously with two different modes, resulting in broadside radiations at two adjacent bands. Threefold objectives of this investigation includes: (i) to realize HEM{12\delta} mode in a practical CDRA without involving any unwanted hybrid mode; (ii) to explore composite aperture type feed, which serves as equivalent magnetic and electric dipoles to launch HEM{11\delta} mode and HEM{12\delta} mode, respectively; and hence (iii) to achieve a dual-mode dualband CDRA without compromising in any enlargement of antenna dimension. HEM{12\delta} mode is a recent introduction by the present authors as a broadside radiating mode in a CDRA, although this investigation demonstrates a practically feasible application for the first time. Systematic study of newly proposed composite aperture is followed by experimental investigation with a set of prototypes operating at S and C bands. As much as 6 dBi gain with 7–8% matching bandwidth for each operating band has been experimentally demonstrated. [ABSTRACT FROM PUBLISHER]

This study proposes an accurate estimation of whole-body averaged specific absorption rate (WBA-SAR) for far-field exposure of an isolated human body in the frequency range of 10-200MHz based on a lossy homogenous cylindrical antenna model of the human body. Equations are derived for the total induced axial current and the whole-body averaged SAR based on a rigorous treatment of cylindrical antenna theory. An explicit formula for the resonance frequency in terms of the anatomical parameters and the dielectric properties of the body is proposed for the first time. Moreover, important phenomena in far-field radio frequency (RF) dosimetry, such as, the cause of resonance and the SAR frequency characteristics are discussed from an antenna theory perspective. [ABSTRACT FROM AUTHOR]

A multipatch configuration of probe-fed rectangular microstrip antennas mounted on a cylindrical body, with electrically small radius, with an arbitrary number of substrate and superstrate layers is investigated in this paper. A full-wave analysis and a moment-method calculation are employed. A unified procedure for creating proper matrices for the investigated geometry of the structure is outlined here. Numerical results for the input impedances and radiation patterns are calculated and verified by comparing them with results from the literature and our own measurements of manufactured prototypes. [ABSTRACT FROM PUBLISHER]

A quadrature feed circularly polarized (CP) cylindrical dielectric resonator antenna (DRA) aiming for wideband application is proposed in this paper. The proposed CP DRA is fed with a quadrature feed network, which consists of a Wilkinson divider and a wideband 90° shifter designed with a switched line structure. The feed network can provide good impedance matching, balanced power splitting, and consistent 90° phase shifting over a wide bandwidth. The proposed CP DRA is designed using a cylindrical dielectric resonator with simple structure, and simulated using HFSS 12.0. The simulations indicate that the proposed antenna has good impedance and circular polarization characteristics. The prototype of the antenna is fabricated and measured. The measurements and the simulations agree well, and the measured results exhibit an impedance bandwidth (VSWR ≤ 2) of 43.3%, an axial ratio (AR) bandwidth (AR ≤ 3 dB) of 42.8%, and a 3 dB gain bandwidth of 40.8%. [ABSTRACT FROM AUTHOR]

A thin mantle cloak is described for electromagnetic footprint reduction for arrays of thin cylinders. The cloaking is obtained by covering the conformal geometry with a metasurface having as a unit cell that is a width modulated microstrip line. Enfoldings at different angles have been considered and numerically studied both for single and multiple cylinders. Frequency scalability and polarization sensitivity of the geometry has also been considered. Experimental results obtained at K-band are in good agreement with numerical data and demonstrate the applicability of the proposed approach for wide-band (\approx 16\%) cloaking applications. The performance of the proposed solution has been compared with available data in the literature, and its superiority has been demonstrated. [ABSTRACT FROM PUBLISHER]