Numerical implementation of the mixed potential integral equation for planar structures with ferrite layers arbitrarily magnetized

This work presents a new implementation of the mixed potential integral equation (MPIE) for planar structures that can include ferrite layers arbitrarily magnetized. The implementation of the MPIE here reported is carried out in the space domain. Thus it will combine the well-known numerical advantages of working with potentials as well as the flexibility for analyzing nonrectangular shape conductors with the additional ability of including anisotropic layers of arbitrarily magnetized ferrites. In this way, our approach widens the scope of the space domain MPIE and sets this method as a very efficient and versatile numerical tool to deal with a wide class of planar microwave circuits and antennas.Ministerio de Educación y Ciencia TEC2004-0321

Physically-insightful equivalent circuit models for electromagnetic periodic structures

In this presentation it will be discussed how to obtain analytical or quasi-analytical equivalent circuits to deal with periodic structures such as frequency selective surfaces and/or metasurfaces. Both the topology and the values of the involved elements of these circuits are obtained from a basic rationale to solve the corresponding integral equation. This procedure, besides providing a very efficient analysis/design tool, allows for a good physical insight into the operating mechanisms of the structure in contrast with the almost blind numerical scheme of commercial simulators.Ministerio de Economía y Competitividad TEC2013-41913-PJunta de Andalucía P12-TIC-143

Some advances in the circuit modeling of extraordinary optical transmission

The phenomenon of extraordinary optical transmission (EOT) through electrically small holes perforated on opaque metal screens has been a hot topic in the optics community for more than one decade. This experimentally observed frequency-selective enhanced transmission of electromagnetic power through holes, for which classical Bethe's theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was first linked to the plasma-like behavior of metals at optical frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made evident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at optical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch) supported by the periodically perforated plate. The authors of this paper have recently proposed an alternative model whose details will be briefly summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide additional insight.Ministerio de Ciencia e Innovación TEC2007-65376, CSD2008-0006

On the Computation of the Dispersion Diagram of Symmetric One-Dimensionally Periodic Structures

A critical discussion on the computation of the dispersion diagram of electromagnetic guiding/radiating structures with one-dimensional periodicity using general-purpose electromagnetic simulation software is presented in thiswork. In thesemethods, full-wave simulations of finite sections of the periodic structure are combined with appropriate simplifying network models. In particular, we analyze the advantages and limitations of two different combined methods, with emphasis on the determination of their range of validity. Our discussion is complemented with several selected numerical examples in order to show the most relevant aspects that a potential user of these methods should be aware of. Special attention is paid to the relevant role played by the high-order coupling between adjacent unit cells and between the two halves of unit cells exhibiting reflection, inversion, and glide symmetries.Ministerio de Ciencia, Innovación y Universidades TEC2017-84724-

Circuit model for a periodic array of slits sandwiched between two dielectric slabs

This paper proposes an equivalent circuit model that uses lumped elements and transmission lines to explain the transmission of electromagnetic waves through a conducting screen periodically perforated with slits and sandwiched between two different dielectric slabs. The present model relies on the impedance-matching point of view, previously introduced by some of the authors, rather than on the surface plasmon polariton concept. Thus, the model constitutes a simple and insightful framework that easily leads to accurate qualitative and quantitative predictions about the nature of the transmission spectrum of such structures.Ministerio de Ciencia e Innovación TEC2007-65376, CSD2008-00066Junta de Andalucía TIC-459

Near-field enhanced imaging by a magnetized ferrite slab

This letter demonstrates the near-field imaging enhancement at microwave frequencies of two-dimensional sources by a ferrite slab magnetized to saturation. It is shown that this effect is based on the nonreciprocal amplification of magnetostatic surface waves (MSSW) across the ferrite slab. The inclusion of losses in our analysis has also made it possible to prove this effect for realistic yttrium iron garnet ferrite samples. For ferrite slabs of width d, the resolution at the image plane (at a distance 2d from the source) is better than the resolution in air at a distance d of the source, which leads to an equivalent air length of the ferrite slab less than zero. Since the constitutive parameters of saturated ferrites depend on the external magnetizing field, the operation frequency of the proposed imaging devices can be tuned by varying this biasing field.Ministerio de Ciencia y Tecnología TEC2004-03214, TEC2004-04249-C02-0

2-D analysis of leakage in printed-circuit lines using discrete complex-images technique

The mixed-potential integral equation is combined with the discrete complex-images technique to analyze the complete spectrum of multilayered printed transmission lines. A relevant contribution of the present two-dimensional approach is its ability to study both the bound and leaky regimes in a very simple, systematic, and efficient way. Since, the analysis is carried out in the spatial domain, this method makes it possible to analyze the leakage phenomenon for structures with nonzero-thickness conductors. Efficient quasi-analytical techniques are employed to solve the integral equation

Microstrip circuit analog of a complex diffraction phenomenon

This letter presents a methodology to reproduce at microwave frequencies the physical behavior of certain diffraction structures that have been investigated in the optics community. The methodology will be exemplified with a microstrip circuit implementation of a transmission line system exhibiting an electromagnetic response that mimics the response of simple and compound diffraction gratings. The identification of such "bridge" circuit analogies could be very fruitful for the understanding and development of design strategies to devise practical components based on phenomena employed in the affine areas of optics and microwave engineering.Ministerio de Ciencia e Innovación TEC2007-65376, CSD2008-00066Junta de Andalucía TIC-25

Application of total least squares to the derivation of closed-form green's functions for planar layered media

A new technique is presented for the numerical derivation of closed-form expressions of spatial-domain Green's functions for multilayered media. In the new technique, the spectral-domain Green's functions are approximated by an asymptotic term plus a ratio of two polynomials, the coefficients of these two polynomials being determined via the method of total least squares. The approximation makes it possible to obtain closed-form expressions of the spatial-domain Green's functions consisting of a term containing the near-field singularities plus a finite sum of Hankel functions. A judicious choice of the coefficients of the spectral-domain polynomials prevents the Hankel functions from introducing nonphysical singularities as the horizontal separation between source and field points goes to zero. The new numerical technique requires very few computational resources, and it has the merit of providing single closed-form approximations for the Green's functions that are accurate both in the near and far fields. A very good agreement has been found when comparing the results obtained with the new technique with those obtained via a numerically intensive computation of Sommerfeld integrals.Ministerio de Educación y Ciencia TEC2004-03214Junta de Andalucía TIC-25

On the use of SDA for the analysis of boxed planar lines with complex media

This paper discusses the conditions under which the spectral-domain approach (SDA) can be applied to the analysis of boxed planar lines when complex materials (anisotropic dielectrics, ferrites, magnetoplasmons, chiral media, and so on) are used as substrates. It will be shown that whereas SDA can always be efficiently applied to study laterally open structures, the simultaneous presence of lateral boundary conditions and nonisotropic materials requires further study. Thus, the symmetry properties of the constitutive dyadics that makes possible a rigorous application of the SDA to those kinds of structures will be reported in this paper