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2010-01-05 PIER M Vol. 10, 103-117, 2009. doi:10.2528/PIERM09111802

Analysis of Complex Antenna Around Electrically Large Platform Using Iterative Vector Fields and UTD Method

Zhi-Li He, Kai Huang, and Chang-Hong Liang

A new efficient technique for the analysis of complex antenna around a scatterer is proposed in this paper, termed the iterative vector fields with uniform geometrical theory of diffraction (UTD) technique. The complex field vector components on the closed surface enclosing the antenna without platform are computed by higher order Method of Moments (MOM), and the scattered fields from the platform are calculated by UTD method. The process of iteration is implemented according to the equivalence theorem. Based on this approach, an approximation method is outlined, in which the computational time is saved largely, while the accuracy is not reduced. The relative patterns obtained from the present method and the approximation method both show good agreements with that obtained from MOM.

2010-01-05 PIER M Vol. 10, 93-102, 2009. doi:10.2528/PIERM09101907

Unit Length Parameters, Transition Sharpness and Level of Radiation in Defected Microstrip Structure (DMS) and Defected Ground Structure (DGS) Interconnections

Morteza Kazerooni, Ahmad Cheldavi, and Mohamad Khalil

In this paper, some important concepts about the defected microstrip structure (DMS) and defected ground structure (DGS) interconnections are introduced. In concept number one, three different types of interconnections are analyzed for determining the unit length and frequency dependent characteristics, based on the perturbed direct and return current paths and electromagnetic (EM) simulations. Therefore, the proposed interconnections with nonuniform circuit and ground planes (DMS and DGS) can be modeled using the uniform circuit and ground planes with frequency dependent unit length parameters. This concept can be used for designing the microwave circuits loaded with DMS or DGS. Results show that the unit length parameters are the same at high frequencies but different at low frequencies due to the different current distributions and consequently different geometry shapes. In concept number two, the level of radiation in these interconnections due to the area of defects is determined and compared. The very large radiation, due to large etched area on ground plane, is a deficiency of DGS interconnections. Using the DMS version, the harmful radiation can be decreased effectively. In concept number three, the level of transition from passband to stopband is calculated and compared. Sharper transition can better suppress the band spurious signals. Finally, all performances are tabulated and compared.

2009-12-17 PIER M Vol. 10, 83-91, 2009. doi:10.2528/PIERM09112901

Determination of the Complex Permittivity Values of Planar Dielectric Substrates by Means of a Multifrequency PSO-Based Technique

Renzo Azaro, Federico Caramanica, and Giacomo Oliveri

In this paper, an innovative technique for the determination of the dielectric properties of planar substrates is presented. Starting from a set of impedance measurements performed on a section of a microstrip transmission line built on the planar dielectric substrate under test, the proposed technique formulates the reconstruction problem in terms of an optimization one successively solved by means of an effective stochastic algorithm. Such a method allows one the reconstruction of the permittivity values at multiple frequencies by simply using a vector network analyzer and a standard calibration procedure for the impedance measurement. The results of some representative experimental tests are shown for a preliminary assessment of the effectiveness of the proposed approach.

2009-12-16 PIER M Vol. 10, 71-81, 2009. doi:10.2528/PIERM09111907

Accurate Synthesis Formulas Obtained by Using a Differential Evolution Algorithm for Conductor-Backed Coplanar Waveguides

Sabri Kaya, Kerim Guney, Celal Yildiz, and Mustafa Turkmen

In this paper, accurate synthesis formulas obtained by using a differential evolution (DE) algorithm for conductor-backed coplanar waveguides (CBCPWs) are presented. The synthesis formulas are useful to microwave engineers for accurately calculating the physical dimensions of CBCPWs. The results of the synthesis formulas are compared with the theoretical and experimental results available in the literature. A full-wave electromagnetic simulator IE3D and experimental results are obtained in this work. The average percentage error of the synthesis formulas obtained by using DE algorithm is computed as 0.67% for 1086 CBCPW samples having different electrical parameters and physical dimensions, as compared with the results of quasi-static analysis.

2009-12-13 PIER M Vol. 10, 59-70, 2009. doi:10.2528/PIERM09102202

Enhancement of Electromagnetic Force by Localized Fields in One-Dimensional Photonic Crystal

Jian Ming Li, Tian Lin Dong, and G. J. Shan

In 1-D photonic crystal with structural defects, localized mode results in strong electromagnetic fields around the position of the defect. Thus, the strong fields enhance the tangential force on a lossy dielectric layer, as well as normal force on the perfect dielectric slab. The results of this study suggest a class of micro-machines driven by electromagnetic wave, such as sunlight or microwave.

2009-12-08 PIER M Vol. 10, 49-57, 2009. doi:10.2528/PIERM09102601

Design of TM0n - Mode Couplers for Diagnostics of a Vircator

M. Sumathy, S. K. Chhotray, D. Senthil Kumar, K. S. Bhat, and Lalit Kumar

The waveguide and the coaxial-probe type wideband high power TM0n-mode couplers (n=1,2) were designed and qualified with respect to the coupling factor using the wheel-type mode launchers. The mode launchers and the mode couplers were simulated and experimentally tested, the former for the VSWR and the latter for the coupling factor. The coupler chamber has been used in single-shot experiments, the values of the measured frequencies of coupled output of a typical vircator agreed with those predicted values by particle-in-cell code simulation using MAFIA.

2009-12-08 PIER M Vol. 10, 39-47, 2009. doi:10.2528/PIERM09102008

Study of Mode Propagation in Pseudochiral Transmission Lines

Hossein Hatefi-Ardakani and Jalil Rashed-Mohassel

In this paper, a generic planar transmission line filled, homogeneously, with a pseudochiral omega medium is considered. It is shown that only a uniaxial omega medium can support TE and TM modes separately. Thus, for such a medium, the fields and modal equations for TE, TM and TEM mode propagation are obtained. The special case of parallel plate waveguide is solved, and the effect of pseudochirality parameter Ω on the propagation constant and cut-off frequency is considered. For TEM propagation, an equivalent circuit is given which is different from the common isotropic transmission line model. Finally, a pseudochiral stripline is analyzed, and the elements of the equivalent circuit are calculated. The results show that the properties of the line vary as the pseudochirality parameter changes.

2009-12-01 PIER M Vol. 10, 25-38, 2009. doi:10.2528/PIERM09110507

Comparative Analysis of Split-Ring Resonators for Tunable Negative Permeability Metamaterials Based on Anisotropic Dielectric Substrates

Jiun-Yeu Chen, Wang-Lin Chen, Jia-Yi Yeh, Lien-Wen Chen, and Ching-Cheng Wang

The magnetic resonance of various split ring resonators (SRRs) is numerically investigated to analyze the dependence of the resonance frequency on their parameter designs. The behavior of the magnetic resonance frequency in the configuration of the 2-cut single-ring SRR (2C-SRR) shows a larger shift in relation to the changes of the SRR size scaling, split width and substrate permittivity. A new magnetic particle formed by the 2C-SRR structure incorporating nematic liquid crystals (LCs) into the multilayered substrate is proposed for the realization of a tunable magnetic metamaterial. When using such inclusions, the tuning range of the magnetic resonance conditions could be as wide as ~1.1 GHz via changing the orientation of LC molecules by 90°.

2009-12-01 PIER M Vol. 10, 13-24, 2009. doi:10.2528/PIERM09110514

An External Cloak with Arbitrary Cross Section Based on Complementary Medium

Chengfu Yang, Ming Huang, Jingjing Yang, Zhe Xiao, and Jinhui Peng

Electromagnetic cloak is a device which makes an object "invisible" for electromagnetic irradiation in a certain frequency range. Material parameters for the complementary medium-assisted external cylindrical cloak with arbitrary cross section are derived based on combining the concepts of complementary media and transformation optics. It can make the object with arbitrary shape outside the cloaking domain invisible, as long as an "antiobject" is embedded in the complementary layer. The external cloaking effect has been verified by full-wave simulation. Moreover, the effect of metamaterial losses is studied, and small losses less than or equal to 0.01 do not disturb the cloaking effect.

2009-12-01 PIER M Vol. 10, 1-12, 2009. doi:10.2528/PIERM09102602

Grid- Based Global Electromagnetic Simulation Tool for Parametric Distributed Analysis of Array Antennas

Fadi Khalil, Herve Aubert, Fabio Coccetti, Petr Lorenz, and Robert Plana

Full-wave electromagnetic solver based on the Transmission Line Matrix Method has been deployed on Grid test-bed. This Grid-based electromagnetic approach exploits the availability of computing node at disposal through the Grid to face the demand of arbitrary large simulations by allocating a corresponding amount of resources hence minimizing the overall elapse time. In order to highlight the benefits of using computing Grids in electromagnetic simulations, a parametric study of planar reflectarray antennas based on microstrip technology has been carried out. The efficiency of distributed computing when a very large number of computation units (nodes) are involved in the computation of large and non-uniform reflectarray antennas is reported.