Showing papers by "Francisco Medina published in 2003"
TL;DR: In this article, a quasi-analytical and self-consistent model was developed to compute the polarizabilities of split ring resonators (SRRs) and an experimental setup was also proposed for measuring the magnetic polarizability of these structures.
Abstract: This paper develops a quasi-analytical and self-consistent model to compute the polarizabilities of split ring resonators (SRRs). An experimental setup is also proposed for measuring the magnetic polarizability of these structures. Experimental data are provided and compared with theoretical results computed following the proposed model. By using a local field approach, the model is applied to the obtaining of the dispersion characteristics of discrete negative magnetic permeability and left-handed metamaterials. Two types of SRRs, namely, the so-called edge coupled- and broadside coupled- SRRs, have been considered. A comparative analysis of these two structures has been carried out in connection with their suitability for the design of metamaterials. Advantages and disadvantages of both structures are discussed.
805 citations
TL;DR: The authors show that the choice of adequate basis functions in the approximation of the current density induced on the plate makes it possible to obtain very accurate results for the scattered fields while using low computer memory requirements and short CPU times.
Abstract: The method of moments in the Hankel transform domain is applied to the determination of the fields scattered by a conducting circular plate buried in a lossy dispersive half-space when the plate is illuminated by a plane wave. The scattered fields obtained in the frequency domain are used to model the time-domain short-pulse scattering via the inverse fast Fourier transform. The authors show that the choice of adequate basis functions in the approximation of the current density induced on the plate makes it possible to obtain very accurate results for the scattered fields while using low computer memory requirements and short CPU times. This implies that the algorithm developed for the particular problem treated in this paper provides a good benchmark for the validation of any other numerical algorithms dealing with the analysis of the scattering from buried conducting objects with more complex geometry.
28 citations
22 Jun 2003
TL;DR: In this article, the split ring resonator (SRR) loaded waveguide is used as a simulator of a left-handed medium (LHM) for the simulation of negative magnetic permeability media (NMPM) and used for the study of wave propagation in these media.
Abstract: The recently proposed split ring resonator (SRR) loaded waveguide as a simulator of a left-handed medium (LHM) is extended to the simulation of negative magnetic permeability media (NMPM) and used for the study of wave propagation in these media. The experimental results are compared with those provided by the discrete metamaterial (LHM and NMPM) theory. Good qualitative and acceptable quantitative agreement has been found between theory and experiments.
12 citations
TL;DR: Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of stacked circular microstrip patches fabricated on a two-layered substrate which may be made of a uniaxial anisotropic dielectric, a magnetized ferrite or a chiral material as discussed by the authors.
Abstract: Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of stacked circular microstrip patches fabricated on a two-layered substrate which may be made of a uniaxial anisotropic dielectric, a magnetized ferrite or a chiral material. Concerning the case of stacked patches printed on magnetized ferrites, the results show that substantial RCS reduction can be achieved inside the tunable frequency band where magnetostatic mode propagation is allowed. It is also shown that both the frequency and the level of the RCS peaks obtained for circular patches fabricated on anisotropic dielectrics or chiral materials may be substantially different from those obtained when substrate anisotropy or substrate chirality are ignored.
12 citations
TL;DR: Galerkin's method in the Hankel transform domain (HTD) is applied to the fast and accurate determination of the resonant frequencies, quality factors and radiation patterns of stacked circular microstrip patches.
Abstract: Galerkin's method in the Hankel transform domain (HTD) is applied to the fast and accurate determination of the resonant frequencies, quality factors and radiation patterns of stacked circular microstrip patches. The stacked metallic patches are assumed to be embedded in a multilayered substrate which may contain isotropic dielectrics, uniaxial anisotropic dielectrics, magnetized ferrites and/or chiral materials. For the case of stacked microstrip patches fabricated on isotropic dielectrics, the numerical results obtained for the resonant frequencies are compared with measurements carried out by the authors and with numerical results computed by means of the electromagnetic simulator "Ensemble". Good agreement is found among all sets of results. Original results are presented for the resonant frequencies of patches fabricated on anisotropic dielectrics and chiral materials, which show that substrate dielectric anisotropy and substrate chirality are not negligible effects. Finally, the results obtained for...
9 citations
TL;DR: In this paper, a new method for the complete characterization of the radiation of magnetostatic surface waves in microstrip transmission lines with longitudinal magnetization is presented, which is based on the analysis of the excitation of leaky modes of microstrip lines and provides both the propagation constant and the complex impedance of the microstrip.
Abstract: This paper presents a new method for the complete characterization of the radiation of magnetostatic-surface waves in microstrip transmission lines with longitudinal magnetization. This method is based on the analysis of the excitation of leaky modes in microstrip lines and provides both the propagation constant and the complex impedance of the microstrip. From these quantities, the radiation resistance and other relevant characteristics of the line can be directly obtained.
8 citations
01 Jan 2003
6 citations
01 Jan 2003
TL;DR: In this paper, the authors performed in-vitro hemodynamic experiments on bench-top cardiovascular system models to gain an understanding of the relationship between blood flow and disease, and compliant vascular replicas based on patient anatomy are required to better simulate hemodynamic flow in the laboratory.
Abstract: Cardiovascular diseases are the primary pathologic abnormalities that lead to the largest number of deaths in the United States today. Researchers have performed in-vitro hemodynamic experiments on bench-top cardiovascular system models to gain an understanding of the relationship between blood flow and disease. Although simplified models and materials provide insight into the disease process, compliant vascular replicas based on patient anatomy are required to better simulate hemodynamic flow in the laboratory.
6 citations
TL;DR: In this article, it was pointed out that the recently reported resonances appearing in split-ring resonators are explained by the magnetoelectric coupling (or bianisotropy) in the tensor polarizability of these particles.
Abstract: It is pointed out that the recently reported resonances appearing in split-ring resonators are explained by the recently reported theory about the magnetoelectric coupling (or bianisotropy) in the tensor polarizability of these particles.
6 citations
TL;DR: In this article, a theory of multiconductor transmission lines that allows for dealing with possible magnetoelectric couplings between the basic circuit quantities: voltage, current, and the per-unit-length charge and flux linkage is presented.
Abstract: This paper presents a theory of multiconductor transmission lines that allows for dealing with possible magnetoelectric couplings between the basic circuit quantities: voltage, current, and the per-unit-length charge and flux linkage. The magnetoelectric coupling is accounted for by the introduction of two new characteristic matrices of the line, the so-called charge and current memductance matrices. The proposed theory is suitable for the description of lines loaded with gyrotropic, bi(iso/aniso)tropic chiral, pseudochiral, and Tellegen media. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 3–9, 2003
TL;DR: In this paper, a transmission-line model is developed for the computation of the insertion loss of magnetostatic-surface wave transducers and measurements are carried out by the authors to check this model.
Abstract: In this paper, a transmission-line model is developed for the computation of the insertion loss of magnetostatic-surface wave transducers and measurements are carried out by the authors to check this model. In a first step of the analysis, closed-form expressions for the solution of the telegrapher's equations for the two microstrip transducers are obtained. The insertion loss is then derived from this solution as a function of three transmission-line parameters, i.e., the propagation constant and the characteristic impedance of the YIG-loaded microstrip line and the mutual inductance between the two microstrips, these quantities being, in general, complex. In a second step, these transmission-line parameters are numerically computed by applying a full-wave method-of-moments technique. Thus, the theoretical results obtained are found to be in good agreement with experimental results.
TL;DR: In this article, the authors show that the direct application of these methods to general problems may lead to inaccurate and even incongruous results, and they show that such methods may not be appropriate for general problems with separable boundaries and lateral homogeneity.
Abstract: The method of lines (MoL) and discrete mode-matching (DMM) method were originally applied to problems with separable boundaries and lateral homogeneity (for instance, layered planar structures). Since then, these methods have been directly applied to structures with non-separable boundaries and/or lateral inhomogeneity. Although these extensions can be justified in certain approximate cases, there has not been sufficient discussion on its mathematical foundation. This paper discusses the above extensions and shows that the direct application of these methods to general problems may lead to inaccurate and even incongruous results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 79–83, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10830
22 Jun 2003
TL;DR: In this paper, the authors apply the method of moments in the spectral domain to the determination of the frequency-dependent scattering parameters of two-port microstrip circuits fabricated on magnetized ferrite substrates.
Abstract: The authors apply the method of moments in the spectral domain to the determination of the frequency-dependent scattering parameters of two-port microstrip circuits fabricated on magnetized ferrite substrates. The results presented show that it is possible to fabricate bandpass filters on magnetized ferrites that can be tuned by varying either the magnitude or the orientation of the bias magnetic field.
01 Oct 2003
TL;DR: In this article, the insertion loss of magnetostatic-surface wave transducers is computed as a function of three transmission line parameters, i.e., the propagation constant and the characteristic impedance of the YIG-loaded microstrip line and the mutual inductance between the two microstrips.
Abstract: A method is shown for the computation of the insertion loss of magnetostatic-surface wave transducers. In the first step of the method, a closed-form expression is derived for the solution of the telegrapher's equations for the microstrip transducers. The insertion loss is then obtained from this solution as a function of three transmission line parameters, i. e., the propagation constant and the characteristic impedance of the YIG-loaded microstrip line and the mutual inductance between the two microstrips. In the second step, these transmission line parameters are numerically computed by applying a full-wave method of moments technique. The theoretical results obtained have been found to be in good agreement with experimental results.
01 Jan 2003
TL;DR: In this paper, a new method for the complete characterization of the radiation of magnetostatic surface waves in microstrip transmission lines with longitudinal magnetization is presented, which is based on the analysis of the excitation of leaky modes and provides both the propagation con- stant and complex impedance of the microstrip.
Abstract: This paper presents a new method for the complete characterization of the radiation of magnetostatic-surface waves in microstrip transmission lines with longitudinal magnetization. This method is based on the analysis of the excitation of leaky modes in microstrip lines and provides both the propagation con- stant and the complex impedance of the microstrip. From these quantities, the radiation resistance and other relevant characteris- tics of the line can be directly obtained.