Vladimir Volski

Engineering the Input Impedance of Optical Nano Dipole Antennas: Materials, Geometry and Excitation Effect

An optical nano dipole antenna is analyzed by means of its input impedance as well as the matching properties of the antenna topology and material configuration. A comparison of this classical microwave driving method with plane wave excitation is accomplished, contrasting the resonances in the input impedance and optical cross sections for several setups, and analyzing the spectral response shape. It is found that for all structures analyzed, a simple linear expression can be defined characterizing the relation between total dipole length and resonant wavelength. The fact that this linear relationship remains valid for different excitation models, for most widely used antenna materials (Au, Ag, Cu, and Al) and even in the presence of substrates is important with respect to practical designs. To our knowledge, such an extensive study has not been performed before.

On the use of the method of moments in plasmonic applications

In the last 40 years the Method of Moments has been a cornerstone in the field of computational electromagnetics for antennas and other components in the microwave frequency range. In this paper, the applicability, advantages and disadvantages of this method are discussed in view of applying it at much higher frequencies, namely in the field of plasmonics.

Comparison of electromagnetic shielding effectiveness of conductive single jersey fabrics with coaxial transmission line and free space measurement techniques

The aim of this study is to investigate the electromagnetic shielding effectiveness (EMSE) of thin and lightweight knitted fabrics that are suitable for casual wear like t-shirts. For the purpose of having a low production cost, metal/cotton conductive composite yarns are produced by a yarn doubling technique, involving stainless steel wires (35 μm, 50 μm) or copper wires (50 μm, 70 μm) and Ne30/1, Ne40/1, Ne60/2, Ne80/2 count cotton yarns. Single jersey fabrics are knitted on an E20 circular knitting machine with the same machine settings. Coaxial transmission line and free space measurement (by using an anechoic chamber) techniques are used for the EMSE measurements in the frequency range of 100 MHz–1.5 GHz and 1 GHz–18 GHz respectively. The free space measurement technique test results reveal that single jersey knitted fabrics have EMSE ability for the electric field polarization in the same direction as the main direction of the conductive metal wires in the fabric. It is observed that all single jersey fabric structures have more than 7 dB (80% or better) EMSE for GSM-850 and GSM-900 cellular phone communication bands according to coaxial transmission line equipment test results. SNK test results of both test methods reveal that, while 100% cotton fabrics do not have EMSE ability, cotton yarn count is highly significant on the EMSE of single jersey fabrics with conductive composite yarns. Fabrics with two-ply fine cotton yarns (Ne60/2 and Ne80/2) have higher EMSE values than the fabrics with one-ply cotton yarn of the same yarn count (Ne30/1 and Ne40/1).

Radiation patterns of sources placed near the truncation of a semi-infinite dielectric structure: the demonstration case of a magnetic line current

Numerical methods are presented to estimate the radiation pattern of a magnetic line current placed near the truncation of a dielectric structure. The problem is solved using the integral equation technique, expansion wave concept, and physical optics approximation. The comparison between different methods permits to understand better the possibilities of each of the methods.

Optimal Design of a Highly Compact Low-Cost and Strongly Coupled 4 Element Array for WLAN

A 4 element array of microstrip E shaped patches is designed for use in wireless local area network (WLAN) applications. The operating frequency range is from 3.4 to 3.8 GHz and the gain of the array is more than 13 dB. The main beam direction is normal to the ground plane. Considering the specifications given, the focus is on the reduction of occupied space. This implies the use of an integrated feeding technique in combination with highly coupled array elements. Although the concept was published before, no optimizers were used and the previous design did not meet the 10 dB matching criterion. It is clearly proven that, due to its complexity, this innovating topology can be fully taken advantage of only by designing it using efficient evolutionary optimizers. Both a particle swarm optimization (PSO) and a genetic algorithm (GA) technique are used. During the optimization process, the fitness is evaluated by using a full wave solver based on the method of moments (MOM). It is shown that for these types of structures, a single step optimization procedure is preferred, and PSO outperforms GA. CST EM Studio is used for validation purposes before manufacturing. A prototype array is fabricated and measured.

A dedicated technique to measure shielding effectiveness of textiles using a two‐horn antenna set‐up

In response to the concern about growing electromagnetic radiation levels, special clothes, bedcovers, and curtains made from shielding textiles are already available. In some cases claimed shielding properties are incredibly high. The goal of this paper is to introduce a simple measurement method dedicated to textiles. A free space two‐horn set‐up in combination with a post‐processing technique is used to determine shielding effectiveness. At higher frequencies, a simple wireless link with two horn antennas can be used. This type of measurement tends to show high oscillations, especially when the samples are in the order of a wavelength or smaller. This is due to multiple reflections and diffractions. These oscillations can be smoothened using fitting techniques or a post‐processing procedure based on a simulated Gaussian pulse in time domain. The proposed procedures are tested for different textile topologies in the frequency range 1–5 GHz.

Diffraction of a surface wave at the truncation of a dielectric structure

A numerical method to investigate the diffraction of a surface wave at the edges of a truncated dielectric structure is presented. The method is based on the equivalence principle. The current distribution is found from the relevant integral equation obtained from the condition of continuity of the tangential magnetic field. The diffraction pattern and the reflection coefficient of the surface wave are computed after the solution of the integral equation by the Galerkin method. The numerical results show the influence of the substrates permittivity and thickness on the radiation parameters.

Omnidirectional Wideband E-Shaped Cylindrical Patch Antennas

Two novel wideband cylindrical microstrip array antennas (CMAAs) are proposed. They involve two symmetrically located probe-fed E-shaped radiating elements mounted on a cylindrical ground platform. The first design consists of two E-shaped patches located on a textile circular dielectric substrate. The second design involves a radiating element consisting of four strongly coupled E-shaped patches. For both CMAAs, the design has been performed using CST Microwave Studio. In both cases, an omnidirectional radiation pattern (ORP) in the horizontal plane with a deviation of less than 3 dB (maximum over minimum) is obtained. The two antennas are operational at 3.4 and 3.3 GHz with realized bandwidths of 33% and 21% and peak gain values of 2.98 and 4.56 dBi, respectively. A - 10 dB sidelobe level is reached in the vertical plane for the second antenna. The CMAA with the higher gain has been fabricated and measured. Above the - 10 db Breflection level, simulations and measurements are in good agreement.

Quasi 3-D Mixed Potential Integral Equation Formulation for Periodic Structures

This paper introduces the use of the quasi 3-D mixed potential integral equation formulation for structures with a periodicity in two dimensions. The quasi 3-D formulation allows to use both horizontal and vertical conductors, and dielectric inclusions. The key innovation is the use of an effective algorithm to calculate Periodic Greens Functions (PGFs) for vertical currents in the planar multilayered background medium. This algorithm retains the same scheme as for a single source Greens Function (GF). In both cases, the GFs are calculated via an inverse Fourier transform of the GFs in the spectral domain, which are known in closed form. In order to remedy the poor convergence for small source—observation distances, an asymptotic extraction is used, yielding a very compact algorithm, and acceleration techniques are applied. Simple guidelines are proposed to construct asymptotes having the required leading terms and a good convergence. It is shown that many acceleration algorithms widely used in literature are actually able to perform well only in specific circumstances. As far as the authors can see, there is still no general and robust technique, yielding highly accurate results under all circumstances. Several examples illustrate the efficiency of the technique.

Series-fed microstrip antenna arrays operating at 26 GHz

In point-to-point communication systems, such as satellite communication, antenna with high directivity is needed. The most common way of achieving this requirement is to arrange a number of single elements in an array configuration. The elements of the array are connected using a feeding network. There are two main types of feeding networks, namely: the corporate network and the series feeding network. In the corporate feeding network, there is a free equal path from the source to each of the radiating elements without passing through any other radiator. On the other hand, in the series-fed array the radiators are connected to the same feeding line, such that each element takes its own power and delivers the rest to the next elements. The corporate feeding network provides wider bandwidth than the series feed. A unique feature of the series-feed network is that it allows for titling the main beam of the array via slightly varying the frequency. This range of titling is limited by the bandwidth of the elements and the feeding network.