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2006-08-21 PIER Vol. 63, 319-335, 2006. doi:10.2528/PIER06060604

Fractional Curl Operator and Fractional Waveguides

Akhtar Hussain, Saima Ishfaq, and Qaisar Naqvi

Fractional curl operator has been utilized to study the fractional waveguide. The fractional waveguide may be regarded as intermediate step between the two given waveguides. The two given waveguides are related through the principle of duality. Behavior of field lines in fractional waveguides are studied withresp ect to fractional parameter α.

2006-08-21 PIER Vol. 63, 311-317, 2006. doi:10.2528/PIER06053001

Bandwidth Enhansment of Microstrip Antenna

Abdelmonem Abdelaziz

A novel microstrip antenna with wide bandwidth is presented. Two different radiating elements connected together through a matched section and are embedded on a single layer structure. This new structure offers a dual-band microstrip antenna. By controlling the two resonance frequencies of the two elements, a wide frequency bandwidth of approximately 9% has been achieved. A more bandwidth enhancement, up to 12%, has been achieved by adding two parasitic elements to one element of the proposed antenna. Fabrication and measurement of S11 for the proposed antenna has been done. The measured results have been compared with the simulated results using commercial software HFSS version-8.0.

2006-08-21 PIER Vol. 63, 295-310, 2006. doi:10.2528/PIER06062103

Group Theory Based Design of Isotropic Negative Refractive Index Metamaterials

Nantakan Wongkasem, Alkim Akyurtlu, and Kenneth Marx

Novel isotropic planar and three-dimensional negative refractive index (NRI) metamaterial (MTM) designs consisting of periodically arranged cross structures are developed in the terahertz (THz) frequency regime using group theory. The novel designs not only avoid magnetoelectric coupling but also enable a simplified fabrication process. Using Finite-difference Time-Domain (FDTD) simulations, the design exhibits an NRI passband which is in good agreement with the S-parameters obtained from Fresnels equation. Cross-polarized fields are used to characterize the magnetoelectric coupling mechanism and determination of material properties of the medium via group theory aid in the characterization of the isotropy of the structure. Numerical simulations of a wedge composed of the proposed metamaterials prove the negative refractive index of the models.

2006-08-21 PIER Vol. 63, 279-294, 2006. doi:10.2528/PIER06052902

Vector Circuit Theory for Spatially Dispersive Uniaxial Magneto-Dielectric Slabs

Pekka M. T. Ikonen, Mikhail Lapine, Igor Nefedov, and Sergei Tretyakov

We present a general dyadic vector circuit formalism, applicable for uniaxial magneto-dielectric slabs, with strong spatial dispersion explicitly taken into account. This formalism extends the vector circuit theory, previously introduced only for isotropic and chiral slabs. Here we assume that the problem geometry imposes strong spatial dispersion only in the plane, parallel to the slab interfaces. The difference arising from taking into account spatial dispersion along the normal to the interface is briefly discussed. We derive general dyadic impedance and admittance matrices, and calculate corresponding transmission and reflection coefficients for arbitrary plane wave incidence. As a practical example, we consider a metamaterial slab built of conducting wires and split-ring resonators, and show that neglecting spatial dispersion and uniaxial nature in this structure leads to dramatic errors in calculation of transmission characteristics.

2006-08-21 PIER Vol. 63, 243-278, 2006. doi:10.2528/PIER06051901

Singularity Subtraction Integral Formulae for Surface Integral Equations with Rwg, Rooftop and Hybrid Basis Functions

Ilari Hanninen, Matti Taskinen, and Jukka Sarvas

Numerical solution of electromagnetic scattering problems by the surface integral methods leads to numerical integration of singular integrals in the Method of Moments. The heavy numerical cost of a straightforward numerical treatment of these integrals can be avoided by a more efficient and accurate approach based on the singularity subtraction method. In the literature the information of the closed form integral formulae required by the singularity subtraction method is quite fragmented. In this paper we give a uniform presentation of the singularity subtraction method for planar surface elements with RWG, n̂ x RWG, rooftop, and n̂ x rooftop basis functions, the latter three cases being novel applications. We also discuss the hybrid use of these functions. The singularity subtraction formulas are derived recursively and can be used to subtract more than one term in the Taylor series of the Green's function.

2006-08-21 PIER Vol. 63, 223-242, 2006. doi:10.2528/PIER06052601

A Maxwell Garnett Model for Dielectric Mixtures Containing Conducting Particles at Optical Frequencies

Marina Koledintseva, Richard DuBroff, and Robert Schwartz

Mathematical modeling of composites made of a dielectric base and randomly oriented metal inclusions is considered. Different sources of frequency-dependent metal conductivity at optical frequencies are taken into account. These include the skin-effect, dimensional (length-size) resonance of metal particles, and the Drude model. Also, the mean free path of electrons in metals can be smaller than the characteristic sizes of nanoparticles, and this leads to the decrease in conductivity of the metal inclusions. These effects are incorporated in the Maxwell Garnett mixing formulation, and give degrees of freedom for forming desirable optical frequency characteristics of composite media containing conducting particles.

2006-07-29 PIER Vol. 63, 209-222, 2006. doi:10.2528/PIER06052401

Surface Resonances of Metal Stripe Grating on the Plane Boundary of Metamaterial

Andrey Brovenko, Petr Melezhik, Anatoly Poyedinchuk, and Nataliya Yashina

The paper is devoted to the study of the interaction of the electromagnetic waves with the structure composed of perfectly conducting strip grating, situated on the plane boundary of metamaterial with effective permittivity, depending on the frequency of the wave of excitation. The rigorous solution to the relevant diffraction boundary value problem is developed. The extensive numerical experiments, performed with a help of corresponding algorithm constructed, allowed to establish several regularities in the complicated process of interaction of electromagnetic waves with grating on dispersive metamaterial. The efficient association of analytical and numerical study has provided the understanding of the nature of resonant phenomena appearing in this process.

2006-07-29 PIER Vol. 63, 193-207, 2006. doi:10.2528/PIER06052803

Simulation, Analysis, Design and Applications of Array Defected Microstrip Structure (ADMS) Filters Using Rigorously Coupled Multi-Strip (RCMS) Method

M. Kazerooni and Ahmad Cheldavi

This paper presents a simple method to analyze and design a desired frequency band rejection in microstrip transmission lines with defected signal strip structure. Also some new structures called ADMS have been introduced and compared. The proposed circuits can be applied to various microwave and millimeter wave components. Finally this paper introduces the RCMS method, a very fast and efficient solution that determines current distribution on the cross section of the signal strip with arbitrary defection pattern. One microstrip line with defected patterns is discussed and then modeled using RCMS method. The results of the current and voltage distribution along an ADMS obtained using RCMS method are in good agreement with those obtained using FEKO (a full wave simulator).

2006-07-29 PIER Vol. 63, 171-191, 2006. doi:10.2528/PIER06050803

Simulations of the Left-Handed Medium Using Discontinuous Galerkin Method Based on the Hybrid Domains

Yan Shi and Chang-Hong Liang

The increasing interest in electromagnetic effects in the Left-Handed medium (LHM) requires the formulae capable of the full analysis of wave propagation in such materials. First, we develop a novel technique for discretization of the Lorentz medium model. In order to overcome the instability inherent in the standard perfectly matched layer (PML) absorbing boundary condition (ABC), we derive the modified PML ABC which can be extended to truncate the boundary of LHM. Then a convergent high-order accurate scheme based on triangle domains, discontinuous Galerkin method (DGM), is extended to the new DGM based on hybrid domains, triangle domains and quadrilateral domains. Finally, we adopt the new DGM and modified PML formulations to analysis the electromagnetic phenomena in the LHM. The simulation results show accuracy and stability of the proposed scheme.

2006-07-29 PIER Vol. 63, 153-170, 2006. doi:10.2528/PIER06050201

New Magnetic Field Integral Equation for Antenna System

Geyi Wen

The traditional magnetic field integral equation has been generalized to the study of antenna radiation and coupling problems with the feeding lines included. A rigorous proof of the uniqueness of the new magnetic field integral equation has been presented. Some numerical examples have been expounded to demonstrate the validity of the new magnetic field integral equation formulation.

2006-07-29 PIER Vol. 63, 141-152, 2006. doi:10.2528/PIER06050101

New Gl Method and its Advantages for Resolving Historical Difficulties

Ganquan Xie, Feng Xie, Lee Xie, and Jianhua Li

Abstract-In this paper, we propose two types of new electromagnetic (EM) integral equation systems and their dual integral equation systems. Based on the EM integral equation systems, we propose a GL EM modeling and inversion algorithms. We make finite step iterations to exactly solve these integral equation systems or the EM and seismic differential integral equations in finite sub domains. The Global EM wave field is improved successively by the Local scattering EM wave field in the sub domains. Only 3 x 3 or 6 x 6 small matrices need to be solved in the GL method. There is no artificial boundary for infinite domain in the method; In the GL method, the cylindrical and spherical coordinate singularities are resolved; Our method combines the analytic and asymptotic method and numerical method. It is more accurate than FEM and FD method and Born likes approximation, the GL method is available for all frequencies and high contrast materials. Its solution has O(h2) convergent rate. If the Gaussian integrals are used, the field has O(h4) super convergence. The method is a high perform parallel algorithm with intrinsic self parallelization properties. The method has very simple scheme or no scheme or half scheme such that it has half mesh and no mesh. In the method, we can use both of Riemann and Lebesgue integral that induces a meshless method. We have developed software for 3D/2.5D EM, seismic, acoustic, flow dynamic, and QEM modeling and inversion.

2006-07-29 PIER Vol. 63, 125-140, 2006. doi:10.2528/PIER06042603

Minimizing Crosstalks in Unshielded Twisted-Pair Cables by Using Electromagnetic Topology Techniques

Phumin Kirawanich, J. Wilson, Naz E. Islam, and Susumu Yakura

Crosstalk reduction is analyzed for a reconfigured category-five cable network using electromagnetic topology-based simulation. The reconfigured network results in a marked reduction in inductive near-end crosstalk for the unshielded twisted-pair cable network. Analyses show that half-loop shifting of the generator-pair wires placed next to the receptor is the most effective way to control the near-end crosstalk level. This is primarily due to additional coupling sources induced on receptor wires that effectively deactivate the original cross coupling effect. The analysis also reveals the usefulness of electromagnetic topology-based simulations. The technique applied in this paper is applicable for any large network systems. A sub-network compaction scheme is critical in creating the equivalent junctions that provide a significant reduction in total computational time and total computer memory requirement for analyzing large network systems. For a 5.28-m long cable we have considered in this paper, the results are valid up to 10 MHz.

2006-07-29 PIER Vol. 63, 107-123, 2006. doi:10.2528/PIER06042601

Diffraction of Plane Wave by Two Parallel Slits in an Infinitely Long Impedance Plane Using the Method of Kobayashi Potential

Amjad Imran, Qaisar Naqvi, and Kohei Hongo

We studied the diffraction of E-polarized electromagnetic plane wave by two parallel slits in an infinitely long impedance plane. Analysis is based on the concept of Kobayashi potential. Imposition of required boundary conditions leads to dual integral equations. The dual integral equations can be reduced to matrix equations with the infinite unknowns by using the properties of Weber-Schafheitlin's discontinuous integrals and Jacobi's polynomials. Matrix elements are given in terms of indefinite integrals which are difficult to evaluate analytically. The matrix elements are solved numerically. Diffracted far fields in the upper half space are studied.

2006-08-26 PIER Vol. 63, 89-105, 2006. doi:10.2528/PIER06042501

Rigorous Full Vectorial Analysis of Electromagnetic Wave Propagation in 1D

Juan-Antonio Martinez-Rojas, Jesus Alpuente-Hermosilla, José Piñeiro, and Rocio Sanchez-Montero

We propose a new approach to solve the problem of the propagation of electromagnetic waves in unidimensional media with an arbitrary variation of their dielectric permittivity. This method is deduced from the Maxwell equations with a minimum of approximations and allows a full vectorial description of both the electric and magnetic fields through the direct calculation of their Cartesian coordinates.The problem is then equivalent to the solution of a pair of uncoupled ordinary differential equations. We use a very intuitive, highly accurate, pseudospectral technique to solve these equations. This pseudospectral method is based in a combination of Fourier and polynomial expansions of the solution providing very good precision and excellent stability with a relatively low computational effort. We present a simple model of a photonic crystal as an example of application of this technique to real electromagnetic problems.

2006-07-29 PIER Vol. 63, 75-88, 2006. doi:10.2528/PIER06041803

Field Analysis to Optimize Charge Collection in a Sub-Micron Grated Metal-Semiconductor-Metal Photodetector

S. Kache, N. Kranthi, M. Nizam, Phumin Kirawanich, R. McLaren, Naz E. Islam, A. Sharma, C. Mayberry, and S. Lucero

The effects of different geometries, heights and concentrations per unit area of gratings in the active region of a metal semiconductor metal photo-detector have been analyzed for enhanced charge collection through electromagnetic field analysis. Plots of the electric field amplitude as it propagates from the constricted grating region to a larger cross-section in the active region have been studied for comparison. This study shows that a hatched top cone shaped grating allows for maximum energy transfer into the active region, thus enhancing collection. The height for this structure is also a minimum over all structures, thus making the hatched cone the optimum design for enhanced collection. The cladding of such structures with SiO2 also appears to contribute to increased energy transfer into the substrate.

2006-07-29 PIER Vol. 63, 51-73, 2006. doi:10.2528/PIER06041503

The Method of Images in Velocity-Dependent Systems

Dan Censor

This study investigates the application of image methodology to velocity-dependent wave systems. Special Relativity is used for the analysis of waves scattered by arbitrary moving objects in the presence of a perfectly-conducting plane-interface. The various scenarios considered involve geometrical, material, and kinematic symmetries. Cases discussed include free-space, material media at-rest, and material media in motion, with respect to the plane-interface boundary. The last configuration is elaborated for two different scenarios: the first assumes the same medium velocity throughout space when the plane boundary is removed; the second introduces two symmetrical velocityfields in the half-spaces involved, with a jump in flow direction at the interface. Where the method applies it simplifies the analysis, and the results enrich our yet limited repertoire of canonical problems for relativistic scattering.

2006-07-29 PIER Vol. 63, 33-50, 2006. doi:10.2528/PIER06051601

On a Study of Diffraction and Dispersion Managed Soliton in a Cylindrical Media

Mousumi Ballav and Asesh Chowdhury

Analytical and numerical techniques are developed for the analysis of the solitary pulse propagation in a cylindrical media, where both the dispersion and diffraction management are known to exist. In the first part we treat the situation when there is no diffraction management by a simple analytical approach and show that it is possible to control both spatial and temporal width over one period of the dispersion map. An important out put of our analytical treatment is that we can predict the value of length of the second link and the amount of group velocity dispersion there if the initial conditions are given. Unfortunately since the spatial chirp can not be controlled, the treatment can not be repeated a second time. So for a long distance propagation a different treatment in needed. We then show that for long period of transmission, it is necessary to introduce diffraction management term, the best form turns out to be periodic function of the distanced travelled. The detailed variation of spatial and temporal width, chirp, and amplitude are explicitly given.

2006-07-29 PIER Vol. 63, 21-32, 2006. doi:10.2528/PIER06062201

Inverse for the Skewon Medium Dyadic

Ismo Veikko Lindell

In four-dimensional differential-form representation linear medium relations can be expressed in terms of a medium dyadic mapping the electromagnetic two-form involving the B and E fields to the two-form involving the D and H fields. There does not seem to exist a method to invert the medium dyadic in a coordinate-free manner for the general bi-anisotropic medium. Such an inversion is introduced here for the special class of skewon media which is a 15 parameter subclass of previously studied IB media. The resulting compact analytic expression is verified through two simple tests and an expansion in eigenvectors.

2006-07-29 PIER Vol. 63, 1-20, 2006. doi:10.2528/PIER06051801

Natural-Mode Representation for the Field Reflected by an Inhomogeneous Conductor-Backed Material Layer - TE Case

Edward J. Rothwell

The transient plane-wave field reflected by a conductorbacked, inhomogeneous, planar material layer is considered. The reflected field is written as a natural-mode expansion, and the natural resonance frequencies of the slab are found by solving a homogeneous integral equation for the field within the slab. Several examples are considered, and the natural mode series is verified by comparison to the inverse fast-Fourier transform of the frequency-domain reflected field.