José Represa

Reinterpreting Four-Stage Split-Step FDTD Methods as Two-Stage Methods

In recent years, split-step finite-difference time-domain (SS-FDTD) methods have attracted much attention and many implementations have been developed to improve their accuracy and efficiency. In this communication the equivalence between some of these recently reported techniques and conventional schemes is shown. More specifically, we prove that there are four-stage split-step (4SS)-FDTD algorithms that can be reinterpreted as classic two-stage split-step (2SS)-FDTD schemes yielding the same local truncation errors and numerical dispersion relationships. The analytical results are validated by numerical simulations.

A Multiresolution Model of Transient Microwave Signals in Dispersive Chiral Media

A multiresolution in time domain method is used to model the propagation of transient signals through dispersive chiral media. The modeling of these media requires the computation of convolution integrals, whose resolution level may be increased by introducing wavelets in the time dependence of the fields

Multi-resolution 2D-TLM technique using Haar wavelets

A first approach to a Haar-wavelet based multi-resolution formulation of the TLM method is proposed. The technique exploits the equivalence between TLM and FDTD methods, taking advantage of previous work based on the latter (MRTD). To validate it, we have computed the cutoff frequencies in a rectangular waveguide. Results have been compared with data obtained by the traditional 2D-TLM method, and with the analytical values.

Metamaterials, a chance for high frequency electronics?

Metamaterials are a new kind of artificial media, exhibiting electromagnetic properties not found in nature. In fact, the word “meta” comes from the Greek word meaning “beyond”. Among them, the class of “Left Handed” (LH), also known as “Double Negative” (DNG) metamaterials shows unusual characteristics such as backward waves, negative refraction or reverse Doppler effect. In this paper we will present the fundamentals of metamaterials: structure, electromagnetic properties, characteristics of wave propagation and some applications in high frequency (ranging from GHz to THz) passive circuits. Also, a brief scope of prospective applications in electronic circuitry will be discussed.

2D-TLM model for propagation in biisotropic media

A TLM model suitable to model the propagation of electromagnetic waves in biisotropic media is presented. The main characteristic of the electromagnetic response of such complex media is the cross coupling of the electromagnetic field vectors in its constitutive relationships. In this work, the angle tilt between electric and magnetic field vectors, the intrinsic impedances, the effective parameters of the medium, and the rotation of the polarization plane are computed. The results for a monochromatic source are in very good agreement with the theoretical solution.

TLM simulation of electromagnetic wave propagation in anisotropic moving media

A TLM (Transmission Line Matrix) model suitable to simulate the propagation of waves in moving anisotropic continuous media is presented. As it is well known, an electromagnetic wave propagating in a general medium, moving with respect to its source, experiences a drag by the own medium, which involves a wave velocity dependent on the direction of propagation. In this work, we present a first approach for the case of uniform movement of an anisotropic dielectric medium with respect to an electromagnetic source. Although the technique allows for quantitative results, a special attention is devoted to the simulation of wave fronts: distorted elliptical fronts because a particular kind of anisotropy appears, even in an isotropic medium.