Search results for "Ones electromagnètiques"
showing 9 items of 9 documents
Resonancias de ondas electromagnéticas
1994
Este artículo describe un conjunto de experimentos diseñados para medir las resonancias electromagnéticas de varios sistemas sencillos.
Experiencia de microondas para la observación del efecto Doppler
1991
El estudio cualitativo y cuantitativo del efecto Doppler en ondas electromagnéticas puede realizarse mediante un montaje sencillo de microondas, midiendo a partir del mismo la velocidad de un móvil.
Surface-Impedance Formulation for Hollow-Core Waveguides Based on Subwavelength Gratings
2022
A rigorous Surface Impedance (SI) formulation for planar waveguides is presented. This modal technique splits the modal analysis of the waveguide in two steps. First, we obtain the modes characteristic equations as a function of the SI and, second, we need to obtain the surface impedance values using either analytical or numerical methods. We validate the technique by comparison with well-known analytical cases: the parallel-plate waveguide with losses and the dielectric slab waveguide. Then, we analyze an optical hollow-core waveguide de ned by two high-contrast subwavelength gratings validating our results by comparison with reported values. Finally, we show the potential of our formulati…
Technical memorandum: Mode classification in cylindrical surface waveguides
1987
A new method to analyse the TM-TE field structure of hybrid modes in cylindrical surface waveguides is proposed. This method, as well as others previously suggested, is applied to a dielectric-coated wire with an intervening airgap. Our results reveal that they cannot be classified into quasi-TM and quasi-TE modes. However, a scheme of mode designation is proposed, based more on mathematical properties than on the field structure.
Effects of an intervening airgap on the two fundamental modes of a surface waveguide
1987
The introduction of an intervening airgap in a circular surface waveguide is investigated. The radial field structure and the propagation characteristics of the two fundamental modes are shown, as well as their dependence on the airgap and the frequency. The thickness of the airgap is a new parameter that might be used to improve the propagation characteristics of the surface waveguide as a low-loss transmission line, or to control the penetration of the fields in the surrounding medium, allowing a design of the waveguide as a leaky transmission line.
Microwave experiments on electromagnetic evanescent waves and tunneling effect
1993
A set of experiments is described to measure the decay of electromagnetic evanescent waves and the tunneling effect through an airgap. The experiments are performed using microwaves and have been designed to be carried out by third year students of physics. The proposed experimental setup can be regarded as a quantum mechanical simulator for the one‐dimensional motion of a particle.
FILTER RESPONSE OF RESONANT WAVEGUIDE DIELECTRIC GRATINGS AT PLANE-WAVE CONICAL INCIDENCE
2009
An accurate and efficient formulation is presented for the electromagnetic analysis of dielectric waveguide gratings under plane-wave conical incidence. An arbitrary number of dielectric bars can be placed inside each one-dimension periodic cell, including the effect of dielectric losses. The reflectance of a dielectric waveguide grating under conical incidence is compared with theoretical results presented by other authors, finding a very good agreement. A single-layer reflection filter has been designed centered at λ0=1.5 μm whose spectral and angular responses are shown. For this structure, the effect of the asymmetry of the distribution of the refraction index in the reflectance has bee…
Design & Optimization of Large Cylindrical Radomes with Subcell and Non-Orthogonal FDTD Meshes Combined with Genetic Algorithms
2021
The word radome is a contraction of radar and dome. The function of radomes is to protect antennas from atmospheric agents. Radomes are closed structures that protect the antennas from environmental factors such as wind, rain, ice, sand, and ultraviolet rays, among others. The radomes are passive structures that introduce return losses, and whose proper design would relax the requirement of complex front-end elements such as amplifiers. The radome consists mostly in a thin dielectric curved shape cover and sometimes needs to be tuned using metal inserts to cancel the capacitive performance of the dielectric. Radomes are in the near field region of the antennas and a full wave analysis of th…
A New Approach to the Modeling of Anisotropic Media with the Transmission Line Matrix Method
2021
A reformulation of the Transmission Line Matrix (TLM) method is presented to model non-dispersive anisotropic media. Two TLM-based solutions to solve this problem can already be found in the literature, each one with an interesting feature. One can be considered a more conceptual approach, close to the TLM fundamentals, which identifies each TLM in Maxwell’s equations with a specific line. But this simplicity is achieved at the expense of an increase in the memory storage requirements of a general situation. The second existing solution is a more powerful and general formulation that avoids this increase in memory storage. However, it is based on signal processing techniques and considerabl…