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Sevilla, Spain

Medina F.,University of Seville | Mesa F.,Microwaves Group | Ruiz-Cruz J.A.,Autonomous University of Madrid | Rebollar J.M.,University Politocnica Of Madrid | Montejo-Garai J.R.,University Politocnica Of Madrid
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

Extraordinary transmission through periodic distributions of sub-wavelength holes made in opaque screens has been demonstrated and exhaustively studied along the last decade. More recently, extraordinary transmission has also been predicted and experimentally observed through electrically small diaphragms located inside hollow pipe waveguides. This last phenomenon cannot be explained in terms of surface waves excited along the periodic system (the so-called surface plasmon polaritons). Transverse resonances can be invoked, however, as a sound explanation for extraordinary transmission in this kind of systems. In this paper, a simple waveguide system, exhibiting exactly the same behavior previously observed in periodic 2-D arrays of holes, is analyzed in depth. Analogies and differences with the periodic case are discussed. The theoretical and experimental results reported in this paper provide strong evidence in favor of the point of view emphasizing the concept of impedance matching versus surface wave excitation. The role of material losses is discussed as an important practical issue limiting the maximum achievable subwavelength transmission level. Most of our conclusions can be applied to both periodic arrays of holes and diaphragms in closed waveguides. © 2010 IEEE. Source

Fernndez-Prieto A.,Microwaves Group | Martel J.,Microwaves Group | Medina F.,Microwaves Group | Mesa F.,Microwaves Group
Microwave and Optical Technology Letters | Year: 2010

Modified coplanar waveguide (CPW) edge-coupled bandpass filters with floating conductor strips printed below the coupled-line sections are proposed. These structures allow one to suppress the first undesired spurious passband associated with the nonhomogeneous nature of the dielectric in CPW structures. Also, tight coupling levels can be easily achieved. An optimization code based on a fast quasi-TEM solver is used to optimize the dimensions of the filter sections, in such a way that final dimensions are obtained in less than 1 min. A couple of filters have been built and measured to illustrate the theory. Copyright © 2010 Wiley Periodicals, Inc. Source

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