Francisco Medina Mena - Academia.edu (original) (raw)
Papers by Francisco Medina Mena
In this paper, sub-wavelength transmission resonances with obliquely incident TE and TMpolarized ... more In this paper, sub-wavelength transmission resonances with obliquely incident TE and TMpolarized plane waves are studied in patterned screens formed by symmetric capacitive or inductive grids printed on a dielectric slab. The analysis is based on the dynamic model of the grid with two-sided impedance boundary conditions and a circuit theory model, resulting in the same analytical expressions for the reflection and transmission coefficients. The apparent sub-wavelength resonances of complete transmission correspond to Fabry-Perot type resonances of a dielectric slab loaded with the effective grid admittances.
ABSTRACT The study of the transmission of electromagnetic waves through periodically perforated o... more ABSTRACT The study of the transmission of electromagnetic waves through periodically perforated opaque screens, even though being a very classical topic, has received a renewed attention along the last fifteen years because of the discovery of the exciting phenomenon so-called extraordinary optical transmission [1]. The transmission spectrum of structures consisting on periodic arrays of holes or slits made in electrically thick metal plates has been explained in terms of the surface waves supported by the perforated screens (spoof surface plasmon polaritons). However, some of the authors of this paper have reported simple circuit models accounting for the transmission spectra of a variety of periodically perforated structures. In this paper we apply the circuit model methodology to explain the details of the transmission spectra of periodic gratings of slits made in thick conducting screens when the slits are geometrically nonuniform. In particular, we study slits with unsymmetrically placed bumps and cuts and tapered slits. The results provided by simple analytical circuit-like models are shown to agree very well with data obtained with a commercial finite elements solver. The availability of analytical models reports obvious advantages over numerical approaches, specially for design purposes.
IEEE Transactions on Antennas and Propagation, 2000
This paper presents an algorithm for the acceleration of the series involved in the computation o... more This paper presents an algorithm for the acceleration of the series involved in the computation of 2-D homogeneous Green's functions with 1-D and 2-D periodicities. The algorithm is based on an original implementation of the spectral Kummer-Poisson's method, and it can be applied to the efficient computation of a wide class of infinite series. In the algorithm the number of asymptotic terms retained in Kummer's transformation is externally controlled so that any of the series that has to be accelerated is split into one series with exponential convergence and another series with algebraic convergence of arbitrarily large order. Numerical simulations have shown that there is an "optimum" number of asymptotic terms retained in Kummer's transformation for which the CPU time needed in the summation of the series is minimized. The CPU times required by Ewald's method for the evaluation of 2-D Green's functions with 1-D and 2-D periodicities have been compared with those required by the present algorithm, and the algorithm has been found to be between 1.2 and 3 times faster than Ewald's method when working in "optimum" operation conditions.
IEEE Antennas and Wireless Propagation Letters, 2000
ABSTRACT Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are... more ABSTRACT Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are shown to support forward, backward, electroinductive, and complex waves. Two CSRR-based lines are considered: 1) stopband microstrip lines simply loaded with CSRRs, and 2) passband microstrip lines loaded with CSRRs and series gaps. The effects of interresonator coupling on bandwidth enhancement are analyzed on the basis of Bloch mode theory by considering the lumped-element equivalent 4-port circuit model of the unit cell. All the propagation modes are captured by the proposed multiterminal Bloch mode theory, from an eigenmode analysis. The results are validated through a commercial eigenmode solver and supported by experimental data.
IEEE Transactions on Antennas and Propagation, 2004
This work reports a numerical method to generate the space-domain Green's functions used... more This work reports a numerical method to generate the space-domain Green's functions used in the mixed potential integral equation (MPIE) formulation for planar structures when arbitrarily magnetized ferrite slabs are present. The presence of ferrite slabs in planar layered structures has been previously accounted for in the framework of the spectral-domain electric field integral equation (EFIE) formulation of the problem.
IEEE Transactions on Antennas and Propagation, 2000
Applied Physics Letters, 2009
This letter provides an experimental demonstration of extraordinary transmission in a closed wave... more This letter provides an experimental demonstration of extraordinary transmission in a closed waveguide system loaded with an electrically small diaphragm. This is a situation where the standard surface plasmon polariton ͑SPP͒ theory does not apply. The theoretical explanation is then based on the concept of impedance matching. This concept has previously been applied by some of the authors to account for enhanced transmission in situations where surface plasmon theory can be used: periodic arrays of small holes or slits in flat metal screens. The experiment in this letter supports the impedance matching model, valid for when SPPs are present or not.
Applied Physics Letters, 2010
This paper proposes an equivalent circuit model that uses lumped elements and transmission lines ... more 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.
IEEE Transactions on Antennas and Propagation, 2003
This paper develops a quasi-analytical and self-consistent model to compute the polarizabilities ... more 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.
Applied Physics Letters, 2009
ABSTRACT
The phenomenon of extraordinary optical transmission (EOT) through electrically small holes perfo... more 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.
ABSTRACT The study of the transmission of electromagnetic waves through sub-wavelength apertures ... more ABSTRACT The study of the transmission of electromagnetic waves through sub-wavelength apertures has been a very popular topic since the discovery of the phenomenon so-called extraordinary transmission. Some of the authors have recently presented useful models to deal with this phenomenon in a very simple manner. Following this research line, in this contribution an analytical circuit-like model is proposed to characterize the transmission of electromagnetic waves through electrically thick conducting diffraction gratings having internal structure. This means that the slits conforming the grating are not internally uniform. The analysis of this kind of structures has been recently carried out using full-wave solvers, which demand lengthy calculations and provide poor physical insight. Our circuit-based approach, previously demonstrated for other uniform structures, is adapted here to account for 1D arrays of slits having width steps. It is shown that a closed-form expression for the transmissivity can be found. The consequences of the internal structure are studied making use of our simplified model.
IEEE Transactions on Antennas and Propagation, 2000
An analytical circuit model is obtained to study the reflection of TM polarized electromagnetic w... more An analytical circuit model is obtained to study the reflection of TM polarized electromagnetic waves that impinge obliquely on a 1-D periodic corrugated surface consisting of dielectric-loaded T-shaped planar corrugations backed by an infinite ground plane. The model is based on transmission line theory and equivalent lumped-element circuits. For the case of perfect conductors, the topology of the circuit is directly inferred from a rigorous full-wave formulation of the periodic problem without using any heuristic argument. This procedure leads to fully analytical expressions for all the circuit parameters. Ohmic losses are further incorporated in the model under the assumption of strong skin effect. The results thus obtained are compared with those given by an accurate Method of Moments numerical code and HFSS software showing a very good agreement. The strong numerical efficiency as well as the good physical insight provided by the present equivalent circuit model can be advantageously employed for the analysis and/or design of a variety of devices. As examples of the latter, the circuit model is used for the first-stage design of an electrically thin hard impedance surface, a corrugated surface that prevents specular reflection, and an absorber.
IEEE Microwave and Wireless Components Letters, 2000
ABSTRACT
Applied Physics Letters, 2005
This letter demonstrates the near-field imaging enhancement at microwave frequencies of two-dimen... more 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.
IEEE Microwave and Guided Wave Letters, 2000
I. INTRODUCTION THE field theory of the quasi-TEM approximation for two-[1] and multiconductor [2... more I. INTRODUCTION THE field theory of the quasi-TEM approximation for two-[1] and multiconductor [2] transmission lines was in the past successfully extended to lines on reciprocal anisotropic [3] and lossy substrates [4]. Ferrite substrates magnetized along the direction of ...
The aim of this paper is to propose a new simple design of a ultra-wide bandpass filter (3.1 to 1... more The aim of this paper is to propose a new simple design of a ultra-wide bandpass filter (3.1 to 10.6 GHz) based on the cascading of a low pass and a high pass section. They are separately designed using convenient structures leading to compactness and easy fabrication. A stepped impedance structure providing elliptic response has been used for the low
IEEE Transactions on Microwave Theory and Techniques, 2000
For original paper see Antonini et al., ibid., vol.47, no.7, pp.979-85 (July 1999). In the origin... more For original paper see Antonini et al., ibid., vol.47, no.7, pp.979-85 (July 1999). In the original paper, Antonini et al. discussed some questions concerning the AC internal impedance of rectangular cross-sectional conductors (such as those typically used as transmission lines and interconnects in many microwave and digital printed circuits). In this paper the authors comment on their results, and a
The authors present a computationally efficient technique for the analysis of extraordinary trans... more The authors present a computationally efficient technique for the analysis of extraordinary transmission through both infinite and truncated periodic arrays of slots in perfect conductor screens of negligible thickness. An integral equation is obtained for the tangential electric field in the slots both in the infinite case and in the truncated case. The unknown functions are expressed as linear combinations of known basis functions, and the unknown weight coefficients are determined by means of Galerkin's method. The coefficients of Galerkin's matrix are obtained in the spatial domain in terms of double finite integrals containing the Green's functions (which, in the infinite case, is efficiently computed by means of Ewald's method) times cross-correlations between both the basis functions and their divergences. The computation in the spatial domain is an efficient alternative to the direct computation in the spectral domain since this latter approach involves the determination of either slowly convergent double infinite summations (infinite case) or slowly convergent double infinite integrals (truncated case). The results obtained are validated by means of commercial software, and it is found that the integral equation technique presented in this paper is at least two orders of magnitude faster than commercial software for a similar accuracy. It is also shown that the phenomena related to periodicity such as extraordinary transmission and Wood's anomaly start to appear in the truncated case for arrays with more than 100 (10 × 10) slots.
In this paper, sub-wavelength transmission resonances with obliquely incident TE and TMpolarized ... more In this paper, sub-wavelength transmission resonances with obliquely incident TE and TMpolarized plane waves are studied in patterned screens formed by symmetric capacitive or inductive grids printed on a dielectric slab. The analysis is based on the dynamic model of the grid with two-sided impedance boundary conditions and a circuit theory model, resulting in the same analytical expressions for the reflection and transmission coefficients. The apparent sub-wavelength resonances of complete transmission correspond to Fabry-Perot type resonances of a dielectric slab loaded with the effective grid admittances.
ABSTRACT The study of the transmission of electromagnetic waves through periodically perforated o... more ABSTRACT The study of the transmission of electromagnetic waves through periodically perforated opaque screens, even though being a very classical topic, has received a renewed attention along the last fifteen years because of the discovery of the exciting phenomenon so-called extraordinary optical transmission [1]. The transmission spectrum of structures consisting on periodic arrays of holes or slits made in electrically thick metal plates has been explained in terms of the surface waves supported by the perforated screens (spoof surface plasmon polaritons). However, some of the authors of this paper have reported simple circuit models accounting for the transmission spectra of a variety of periodically perforated structures. In this paper we apply the circuit model methodology to explain the details of the transmission spectra of periodic gratings of slits made in thick conducting screens when the slits are geometrically nonuniform. In particular, we study slits with unsymmetrically placed bumps and cuts and tapered slits. The results provided by simple analytical circuit-like models are shown to agree very well with data obtained with a commercial finite elements solver. The availability of analytical models reports obvious advantages over numerical approaches, specially for design purposes.
IEEE Transactions on Antennas and Propagation, 2000
This paper presents an algorithm for the acceleration of the series involved in the computation o... more This paper presents an algorithm for the acceleration of the series involved in the computation of 2-D homogeneous Green's functions with 1-D and 2-D periodicities. The algorithm is based on an original implementation of the spectral Kummer-Poisson's method, and it can be applied to the efficient computation of a wide class of infinite series. In the algorithm the number of asymptotic terms retained in Kummer's transformation is externally controlled so that any of the series that has to be accelerated is split into one series with exponential convergence and another series with algebraic convergence of arbitrarily large order. Numerical simulations have shown that there is an "optimum" number of asymptotic terms retained in Kummer's transformation for which the CPU time needed in the summation of the series is minimized. The CPU times required by Ewald's method for the evaluation of 2-D Green's functions with 1-D and 2-D periodicities have been compared with those required by the present algorithm, and the algorithm has been found to be between 1.2 and 3 times faster than Ewald's method when working in "optimum" operation conditions.
IEEE Antennas and Wireless Propagation Letters, 2000
ABSTRACT Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are... more ABSTRACT Transmission-line metamaterials based on complementary split-ring resonators (CSRRs) are shown to support forward, backward, electroinductive, and complex waves. Two CSRR-based lines are considered: 1) stopband microstrip lines simply loaded with CSRRs, and 2) passband microstrip lines loaded with CSRRs and series gaps. The effects of interresonator coupling on bandwidth enhancement are analyzed on the basis of Bloch mode theory by considering the lumped-element equivalent 4-port circuit model of the unit cell. All the propagation modes are captured by the proposed multiterminal Bloch mode theory, from an eigenmode analysis. The results are validated through a commercial eigenmode solver and supported by experimental data.
IEEE Transactions on Antennas and Propagation, 2004
This work reports a numerical method to generate the space-domain Green's functions used... more This work reports a numerical method to generate the space-domain Green's functions used in the mixed potential integral equation (MPIE) formulation for planar structures when arbitrarily magnetized ferrite slabs are present. The presence of ferrite slabs in planar layered structures has been previously accounted for in the framework of the spectral-domain electric field integral equation (EFIE) formulation of the problem.
IEEE Transactions on Antennas and Propagation, 2000
Applied Physics Letters, 2009
This letter provides an experimental demonstration of extraordinary transmission in a closed wave... more This letter provides an experimental demonstration of extraordinary transmission in a closed waveguide system loaded with an electrically small diaphragm. This is a situation where the standard surface plasmon polariton ͑SPP͒ theory does not apply. The theoretical explanation is then based on the concept of impedance matching. This concept has previously been applied by some of the authors to account for enhanced transmission in situations where surface plasmon theory can be used: periodic arrays of small holes or slits in flat metal screens. The experiment in this letter supports the impedance matching model, valid for when SPPs are present or not.
Applied Physics Letters, 2010
This paper proposes an equivalent circuit model that uses lumped elements and transmission lines ... more 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.
IEEE Transactions on Antennas and Propagation, 2003
This paper develops a quasi-analytical and self-consistent model to compute the polarizabilities ... more 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.
Applied Physics Letters, 2009
ABSTRACT
The phenomenon of extraordinary optical transmission (EOT) through electrically small holes perfo... more 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.
ABSTRACT The study of the transmission of electromagnetic waves through sub-wavelength apertures ... more ABSTRACT The study of the transmission of electromagnetic waves through sub-wavelength apertures has been a very popular topic since the discovery of the phenomenon so-called extraordinary transmission. Some of the authors have recently presented useful models to deal with this phenomenon in a very simple manner. Following this research line, in this contribution an analytical circuit-like model is proposed to characterize the transmission of electromagnetic waves through electrically thick conducting diffraction gratings having internal structure. This means that the slits conforming the grating are not internally uniform. The analysis of this kind of structures has been recently carried out using full-wave solvers, which demand lengthy calculations and provide poor physical insight. Our circuit-based approach, previously demonstrated for other uniform structures, is adapted here to account for 1D arrays of slits having width steps. It is shown that a closed-form expression for the transmissivity can be found. The consequences of the internal structure are studied making use of our simplified model.
IEEE Transactions on Antennas and Propagation, 2000
An analytical circuit model is obtained to study the reflection of TM polarized electromagnetic w... more An analytical circuit model is obtained to study the reflection of TM polarized electromagnetic waves that impinge obliquely on a 1-D periodic corrugated surface consisting of dielectric-loaded T-shaped planar corrugations backed by an infinite ground plane. The model is based on transmission line theory and equivalent lumped-element circuits. For the case of perfect conductors, the topology of the circuit is directly inferred from a rigorous full-wave formulation of the periodic problem without using any heuristic argument. This procedure leads to fully analytical expressions for all the circuit parameters. Ohmic losses are further incorporated in the model under the assumption of strong skin effect. The results thus obtained are compared with those given by an accurate Method of Moments numerical code and HFSS software showing a very good agreement. The strong numerical efficiency as well as the good physical insight provided by the present equivalent circuit model can be advantageously employed for the analysis and/or design of a variety of devices. As examples of the latter, the circuit model is used for the first-stage design of an electrically thin hard impedance surface, a corrugated surface that prevents specular reflection, and an absorber.
IEEE Microwave and Wireless Components Letters, 2000
ABSTRACT
Applied Physics Letters, 2005
This letter demonstrates the near-field imaging enhancement at microwave frequencies of two-dimen... more 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.
IEEE Microwave and Guided Wave Letters, 2000
I. INTRODUCTION THE field theory of the quasi-TEM approximation for two-[1] and multiconductor [2... more I. INTRODUCTION THE field theory of the quasi-TEM approximation for two-[1] and multiconductor [2] transmission lines was in the past successfully extended to lines on reciprocal anisotropic [3] and lossy substrates [4]. Ferrite substrates magnetized along the direction of ...
The aim of this paper is to propose a new simple design of a ultra-wide bandpass filter (3.1 to 1... more The aim of this paper is to propose a new simple design of a ultra-wide bandpass filter (3.1 to 10.6 GHz) based on the cascading of a low pass and a high pass section. They are separately designed using convenient structures leading to compactness and easy fabrication. A stepped impedance structure providing elliptic response has been used for the low
IEEE Transactions on Microwave Theory and Techniques, 2000
For original paper see Antonini et al., ibid., vol.47, no.7, pp.979-85 (July 1999). In the origin... more For original paper see Antonini et al., ibid., vol.47, no.7, pp.979-85 (July 1999). In the original paper, Antonini et al. discussed some questions concerning the AC internal impedance of rectangular cross-sectional conductors (such as those typically used as transmission lines and interconnects in many microwave and digital printed circuits). In this paper the authors comment on their results, and a
The authors present a computationally efficient technique for the analysis of extraordinary trans... more The authors present a computationally efficient technique for the analysis of extraordinary transmission through both infinite and truncated periodic arrays of slots in perfect conductor screens of negligible thickness. An integral equation is obtained for the tangential electric field in the slots both in the infinite case and in the truncated case. The unknown functions are expressed as linear combinations of known basis functions, and the unknown weight coefficients are determined by means of Galerkin's method. The coefficients of Galerkin's matrix are obtained in the spatial domain in terms of double finite integrals containing the Green's functions (which, in the infinite case, is efficiently computed by means of Ewald's method) times cross-correlations between both the basis functions and their divergences. The computation in the spatial domain is an efficient alternative to the direct computation in the spectral domain since this latter approach involves the determination of either slowly convergent double infinite summations (infinite case) or slowly convergent double infinite integrals (truncated case). The results obtained are validated by means of commercial software, and it is found that the integral equation technique presented in this paper is at least two orders of magnitude faster than commercial software for a similar accuracy. It is also shown that the phenomena related to periodicity such as extraordinary transmission and Wood's anomaly start to appear in the truncated case for arrays with more than 100 (10 × 10) slots.