Juan R. Mosig

Multilayered media Green's functions in integral equation formulations

A compact representation is given of the electric- and magnetic-type dyadic Greens functions for plane-stratified, multilayered, uniaxial media based on the transmission-line network analog along the aids normal to the stratification. Furthermore, mixed-potential integral equations are derived within the framework of this transmission-line formalism for arbitrarily shaped, conducting or penetrable objects embedded in the multilayered medium. The development emphasizes laterally unbounded environments, but an extension to the case of a medium enclosed by a rectangular shield is also included.

Reflection of an open-ended coaxial line and application to nondestructive measurement of materials

Reflection measurement techniques require a way to correlate measured reflection factors with the permittivity of the materials. This relationship is derived for the open-ended coaxial line propagating the TEM mode.

Reconfigurable terahertz plasmonic antenna concept using a graphene stack

The concept and analysis of a Terahertz (THz) frequency-reconfigurable antenna using graphene are presented. The antenna exploits dipole-like plasmonic resonances that can be frequency-tuned on large range via the electric field effect in a graphene stack. In addition to efficient dynamic control, the proposed approach allows high miniaturization and good direct matching with continuous wave THz sources. A qualitative model is used to explain the excellent impedance stability under reconfiguration. These initial results are very promising for future all-graphene THz transceivers and sensors. Keywords: Reconfigurable antenna, Graphene, Plasmons, Terahertz, frequency-tuning.

A Dynamical Radiation Model for Microstrip Structures

Publisher Summary This chapter deals with the models currently used to improve the quasistatic approximation of microstrip structures. The chapter presents a brief review of the microstrip fundamentals; a comprehensive account of these dynamical models. A particular model based on the calculation of the electric surface currents in the structure is introduced in the chapter. The Greens functions involved are constructed and numerically evaluated using the exact formulation for dipole potentials in a stratified medium. New evaluation techniques developed for Sommerfeld integrals permit a very accurate computation of Greens functions. Their properties are then extensively discussed; the validity of the quasistatic approximations is checked and the importance of the surface wave is pointed out in detail. Finally, the integral equations for the currents are set up and solved by numerical methods in that also give several practical applications. The chapter concludes the model is that the surface currents on the antenna are directly determined and the near field can then be determined easily, that becomes most important when microstrip structures are utilized as radiators or biological applicators.

A subdomain multilevel approach for the efficient MoM analysis of large planar antennas

Reference LEMA-ARTICLE-2000-010doi:10.1002/1098-2760(20000820)26:4 3.0.CO;2-CView record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

A Broadband and High Gain Metamaterial Microstrip Antenna

A broad bandwidth and high gain rectangular patch antenna was specifically designed in this paper using planar-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed strip-line gaps etched on the metal patch and ground plane, respectively. Demonstrated to have left-handed characteristics, the patterned metal patch and finite ground plane form a coupled capacitive-inductive circuit of negative index metamaterial. It is shown to have great impact on the antenna performance enhancement in terms of the bandwidth significantly broadened from a few hundred megahertz to a few gigahertz, and also in terms of high efficiency, low loss, and low voltage standing wave ratio. Experimental data show a reasonably good agreement between the simulation and measured results. This antenna has strong radiation in the horizontal direction for some specific applications within the entire band.

A small microstrip patch antenna with a convenient tuning option

The paper addresses two aspects of resonant microstrip patch antennas, namely, miniaturization and resonant frequency tuning. First, a patch geometry which allows a controllable size reduction over a limited range is presented. The basic shape is circular with slits cut into it. Modification of the slit geometry leads to both linear as well as circular polarized (CP) operation. Second, the use of another patch of a specific shape as a superstrate layer in a stacked configuration allows tuning over a relatively large frequency range as compared to the patch bandwidth. Tuning is accomplished by a simple rotation of the superstrate layer. The use of another superstrate layer allows tunable CP operation. Details on the antenna characteristics have been worked out for two examples, and computations have been compared with measurements where possible. Some design guidelines have also been included.

Comparison of Quasi-Static and Exact Electromagnetic Fields from a Horizontal Electric Dipole Above a Lossy Dielectric Backed by an Imperfect Ground Plane

In most microstrip transmission lines, analysis is made assuming that a quasi-TEM mode exists and propagates down the line. The primary objective of this paper is to obtain the region of validity of this assumption. The second objective of this paper is to derive the expressions for the fields for a horizontal electric dipole over a Iossy dielectric medium backed by an imperfect ground plane. It is shown that, to a first approximation, fields at the air-dielectric interface are independent of the ground plane conductivity. Since we are interested in coupfing between lines, our interest is in the computation of the fields primarily at the air-dielectric interface. Finally, numerical results are presented to show where the quasi-static approximations deviate from the exact solution for a given microstrip geometry as the frequency of operation or the observation point is changed.

A Printed Transition for Matching Improvement of SIW Horn Antennas

The substrate integrated waveguide (SIW) technology allows to construct several types of commonly used antennas in a planar way. However, frequency limitations associated to commercial substrates appear in the implementation of certain types of antennas, e.g., SIW horn antennas are not well matched when the substrate thickness is much smaller than the wavelength. A printed transition is proposed to overcome this problem. Differently from current solutions, no bulky elements are required allowing to maintain the most important features of this technology namely its compactness and ease of manufacturing. In order to quickly analyze and design the transition, both a coupled resonator and a transmission line models are developed, together with design guidelines. The proposed transition is designed to match a H-plane SIW horn antenna built in a thin substrate

Experimental verification of broadband cloaking using a volumetric cloak composed of periodically stacked cylindrical transmission-line networks

({\rm thickness}<\lambda_{0}/10)