IEEE MTT-S 2008 International Microwave Symposium Technical Program

Session: WE1A	Electromagnetic Analysis of Complex Structures
Chair:	Natalia K. Nikolova, McMaster University
Co-Chair:	Ingo Wolff, IMST GmbH
Abstract:	In this session, complex materials and periodic microwave structures are studied. Analyses of interesting structures such as microwave furnaces and power lines for communication are also presented. The audience will get an insight into the electromagnetic theory of metamaterials, interesting techniques combining electromagnetic and thermal simulations, and new microwave components.

WE1A-01	Electromagnetic Wave Propagation in Dispersive Negative Group Velocity Media
1580	S. M. Mikki, A. A. Kishk, University of Mississippi, University, United States
	We study theoretically the propagation of electromagnetic waves in an infinite, isotropic, and homogenous, medium with both temporal and spatial dispersion included. We derive a partial differential equation connecting temporal and spacial dispersion to achieve negative group velocity. An exact solution of the equation is found and is shown to lead to negative-refraction media even when both $\epsilon$ and $\mu$ are positive. The formal solution suggests the possibility to engineer new artificial materials by carefully manipulating the spatial dispersion profile. We also analyze the power flow and suggests a path beyond the group velocity concept.

WE1A-02	Near-Field Focusing Plates
1395	A. Grbic¹, L. Jiang², R. Merlin², ¹University of Michigan, Ann Arbor, United States, ²University of Michigan, Ann Arbor, United States
	Using a modulated grating-like surface, referred to as a near-field focusing plate, we experimentally demonstrate focusing well beyond the diffraction limit. The reported near-field plate achieves a resolution of lambda_o/20 at a frequency of 1.027 GHz, where lambda_o is the free space wavelength. Along with these experimental results, the intrinsic properties of near-field plates are reviewed and a general procedure for design them is outlined.

WE1A-03	Equivalent Circuit Model to Explain Extraordinary Transmission
1268	F. Medina¹, F. Mesa², R. Marques¹, ¹University of Seville, Seville, Spain, ²University of Seville, Seville, Spain
	This work proposes a circuit model based explanation for the extraordinary transmission (ET) of light phenomenon studied in recent scientific literature. ET mainly stands for unexpected transmission of light through periodic arrays of subwavelength holes in a metal screen. The study of this phenomenon has attracted the attention of many scientists working in the fields of Optics and Condensed Matter Physics, giving place to some controversial explanations. The existence of surface plasmons supported by the metal/air interface at optical frequencies has been considered the underlying reason behind ET. Our contribution tries to offer a relatively simple explanation of ET based on conventional waveguide/transmission-line theory. It will be shown how this simplified microwave-engineering standpoint offers satisfactory explanation for most ET findings. Indeed, ET should be expected not only at optical frequencies but also at lower frequencies, when surface plasmons are not possible.

WE1A-04	Propagation and Band Broadening Effect of Planar Integrated Ridged Waveguide in Multilayer Dielectric Substrates
1202	W. Che¹, C. Li¹, P. Russer², Y. L. Chow³, ¹Nanjing University of Science & Technology, Nanjing, China, ²Techische Universitat Munchen, Munich, Germany, ³University of Waterloo, Waterloo, Canada
	To improve the bandwidth of the SIW, a planar ridged substrate-integrated waveguide (RSIW) with a center line of cylindrical posts is proposed. Theoretical design formulas are derived. The bandwidth is defined as between the cutoffs of TE10 and TE20 modes of the RSIW. The modes are made equivalent to those of a transmission line cavity, across the transverse plane, and the cavity is loaded by a ridge of capacitive posts. Good agreements are observed between the theoretical formulas and numerical simulations. A 37% bandwidth enhancement is achieved; in fact, with structures added to increase the post capacitance, still higher bandwidth enhancement is possible.

WE1A-05	Modeling of an Industrial Microwave Furnace for Metal Casting Applications
1635	M. H. Awida¹, N. Shah¹, B. Warren², E. Ripley ², A. E. Fathy¹, ¹University of Tennessee at Knoxville, Koxville, United States, ²BWXT-Y12 National Security Complex, Oak Ridge, United States
	Microwaves can be used efficiently for casting metals using specially designed industrial microwave ovens. Their designs, however, is a challenging multi-physics problem that would require addressing concurrently electromagnetic, thermal, material and chemical issues. In this paper, a simplified model has been developed to model the operation of an industrial mi-crowave oven. Our EM and thermal results were obtained using FEM modeling and have been experimentally validated via a modular chamber using the thermal and electrical measured material properties at elevated temperatures. Such modeling success is very valuable that would help in further optimizing the microwave metal melting technology.

WE1A-06	Investigation of Fields and Currents for Broadband over Power Line (BPL) Communications
1624	A. Lau¹, D. R. Jackson¹, J. T. Williams¹, F. Mesa², J. Bernal³, ¹University of Houston, Houston, United States, ²University of Seville, Seville, Spain, ³University of Seville, Seville, Spain
	The currents induced on overhead power lines and the subsequent fields from them are studied for a high frequency “broadband over power line” (BPL) source. The physical properties of the fields are studied, and the level of the fields is examined to determine the significance of the fields from BPL sources on power lines.

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