Papers by Francisco Medina
IEEE Antennas and Propagation Society International Symposium. Transmitting Waves of Progress to the Next Millennium. 2000 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.00CH37118)
IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450)
The recently proposed Split Ring Resonator (SRR)-loaded waveguide as a simulator of a lefthanded ... more The recently proposed Split Ring Resonator (SRR)-loaded waveguide as a simulator of a lefthanded 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.
IEEE Transactions on Microwave Theory and Techniques, 2001
Applied Physics Letters, 2009
IEEE Transactions on Microwave Theory and Techniques, 2002
The mixed-potential integral equation is combined with the discrete complex-images technique to a... more 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.
IEEE Transactions on Microwave Theory and Techniques, 2015
Physical Review B, 2011
In this paper, we present a simple circuit model to study the absorption of electromagnetic waves... more In this paper, we present a simple circuit model to study the absorption of electromagnetic waves by a multilayer structure with a high impedance surface in the microwave regime. The absorber consists of a stack of twodimensional arrays of sub-wavelength meshes or patches separated by dielectric slabs and backed by a metallic ground plane, with a single resistive sheet placed on the top layer. We observe the appearance of low-frequency resonances of total absorption, which have been identified as the resonances of Fabry-Pérot type associated with the individual reactively loaded dielectric slabs (that are strongly coupled through the subwavelength grids). It is shown that these resonances lie within certain characteristic frequency band defined by the structural parameters of the absorber. The observed resonances are characterized by studying the electromagnetic field behavior using the circuit model and full-wave numerical program. In addition, we show that the patch array absorber provides stable resonances with respect to the angle and the polarization of obliquely incident plane waves.
IEEE Transactions on Antennas and Propagation, 2004
IEEE Microwave and Wireless Components Letters, 2004
A new LC series element based on a modified version of the split rings resonator introduced in [1... more A new LC series element based on a modified version of the split rings resonator introduced in [1] is proposed. Owing to its small electrical size, the new open split ring resonator (OSRR) is a very attractive element for compact bandpass filter design. As an example, we have designed and fabricated a filter to produce a bandpass around the resonance frequency of the employed OSRRs. The filter bandwidth is controlled by the length of the transmission lines connecting the OSRRs. Sharp and deep out-of-band rejection is achieved by cascading several OSRRs. Circuit theory and electromagnetic based simulations reasonably agree with experiments.
Applied Physics Letters, 2004
IEEE Transactions on Antennas and Propagation, 2001
Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the rad... more Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of a circular microstrip patch printed on a substrate which may be an uniaxial anisotropic dielectric, a magnetized ferrite, or a chiral material. The results obtained for circular patches on magnetized ferrites show that the RCS of these patches can be substantially reduced in a tunable frequency band when a bias magnetic field is applied. It is also shown that the results obtained for the RCS of circular patches printed on chiral materials can be substantially different from those obtained when substrate chirality is ignored.
IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450), 2000
The authors apply the method of moments in the spectral domain to the determination of the freque... more 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.
Ieee Transactions on Microwave Theory and Techniques, 1986
Physical Review E, 2016
A wideband equivalent circuit is proposed for the accurate analysis of scattering from a set of s... more A wideband equivalent circuit is proposed for the accurate analysis of scattering from a set of stacked slit gratings illuminated by a plane wave with transverse magnetic or electric polarization that impinges normally or obliquely along one of the principal planes of the structure. The slit gratings are printed on dielectric slabs of arbitrary thickness, including the case of closely spaced gratings that interact by higher-order modes. A-circuit topology is obtained for a pair of coupled arrays, with fully analytical expressions for all the circuit elements. This equivalent circuit is employed as the basis to derive the equivalent circuit of finite stacks with any given number of gratings. Analytical expressions for the Brillouin diagram and the Bloch impedance are also obtained for infinite periodic stacks.
Phys Rev Lett, 2003
A Reply to the Comment by I. G. Kondrat'ev and A. I. Smirnov.
IEE Proceedings H Microwaves, Antennas and Propagation, 1985
In the paper, a simple recurrence formula to obtain the Green's function for multilayered anisotr... more In the paper, a simple recurrence formula to obtain the Green's function for multilayered anisotropic structures, with rectangular boundary conditions involving electric and magnetic walls and open boundaries, allows us to present an unified variational approach in the spectral domain to find both upper and lower bounds on the mode capacitances of a large class of planar transmission structures. Very accurate results are obtained by using appropriate trial functions to approximate the surface charge density on the strips and the interface potential distribution for several significant MIC configurations.
IEEE Transactions on Antennas and Propagation, 2015
ABSTRACT A fully analytical multimodal equivalent circuit is presented for the modeling of the sc... more ABSTRACT A fully analytical multimodal equivalent circuit is presented for the modeling of the scattering of an obliquely incident plane wave by a two-dimensional (2-D) periodic array of metallic patches (or apertures in a metallic screen) embedded in a layered medium. The topology of the equivalent network is rigorously derived in the analysis and all the network parameters are given in closed form. In contrast with the previously reported explicit circuit models, the proposed approach accounts for dynamical effects over a very wide frequency range, which enables the application of the model to a great variety of situations. The key advantages of the reported multimodal network representation are its analytical nature, its extremely low-computational cost and that the physical phenomena involved in the scattering can be easily understood in terms of transmission line and lumped circuital reasonings.
2014 8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, 2014
2013 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2013
ABSTRACT This paper is focused on the analysis of the propagation characteristics of periodic str... more ABSTRACT This paper is focused on the analysis of the propagation characteristics of periodic structures consisting of a host line loaded with split ring resonators (SRRs). It is well known that these structures exhibit stop band functionality in the vicinity of the resonance frequency of the SRRs, and propagation is forward in the transmission bands. However, by enhancing inter-resonators' coupling the forbidden band widens and this enhancement can be interpreted as due to the presence of complex modes. This has been demonstrated through Bloch mode analysis of the multiport equivalent circuit model of the unit cell.
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Papers by Francisco Medina