Showing papers by "Zvonimir Sipus published in 2004"
TL;DR: In this paper, the mutual coupling between rectangular microstrip patches mounted on a spherical structure is studied based on the spectral-domain method of moments (MoM) and an approximate method is developed to calculate coupling between currents located on different patches.
Abstract: The mutual coupling between rectangular microstrip patches mounted on a spherical structure is studied in this paper. The analysis approach is based on the spectral-domain method of moments (MoM). An approximate method is developed to calculate coupling between currents located on different patches. A laboratory model is built to test different configurations of patches and to validate the calculated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 387–391, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11389
18 citations
20 Jun 2004
TL;DR: In this article, the authors used a rectangular evanescent waveguide filled with negative permeability uniaxial meta-material based on capacitively loaded loop as backward-wave meta material in the 350 MHz band and measured the distribution of the magnetic field along the structures with the help of a small loop antenna and network analyzer.
Abstract: The recently introduced concept of one-dimensional subwavelength resonator, which comprises a combination of forward-wave material and backward-wave material, is investigated experimentally. The rectangular evanescent waveguide filled with negative permeability uniaxial meta-material based on capacitively loaded loop was used as backward-wave meta-material in 350 MHz band. The waveguide was interfaced with an ordinary (forward-wave) coaxial transmission line terminated with a sliding short. The overall length of this waveguide-coaxial structure was much shorter than the wavelength. The distribution of the phase of the magnetic field along the structures was measured with the help of a small loop antenna and network analyzer, for different settings of the sliding short. The measurement results proved that is possible to meet resonant conditions on the structure whose overall length is much smaller than a wavelength, as it was previously theoretically predicted.
13 citations
12 May 2004
TL;DR: In this paper, a rectangular waveguide filled with anisotropic uniaxial meta-material with transversal negative effective permeability is analyzed rigorously, and it is shown that such waveguide supports propagation of backward wave below the cut-off frequency, thus, it can be considered as a dual of an ordinary waveguide.
Abstract: A rectangular waveguide filled with anisotropic uniaxial meta-material with transversal negative effective permeability is analyzed rigorously. It is shown that such waveguide supports propagation of backward wave below the cut-off frequency, thus, it can be considered as a dual of an ordinary waveguide. The transversal dimension of the waveguide can be arbitrarily smaller than a half of the wavelength, which may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides filled with different resonant meta-materials in the 7 GHz and 350 MHz frequency bands have been designed, fabricated and tested. The measured results revealed backward-wave pass-band located below the cut off frequency, which is in agreement with theoretical analysis.
8 citations
04 Jul 2004
TL;DR: In this paper, the authors have given an overview of the mathematical description of PMD and demonstrated the deleterious effect on high bit-rates in various simulations preformed by the computer program FiberProp.
Abstract: Polarization mode dispersion (PMD) occurs in the optical fibers due to circular asymmetries of the fiber core. PMD can be described locally as fiber birefringence and globally, the birefringence is combined with random polarization mode coupling. As PMD varies randomly with time and wavelength, it is rather difficult to describe theoretically and must involve the statistical approach. At 10 Gbit/s PMD is no more negligible and at higher bit-rates (40 Gbit/s and more) it represents the major limitation in optical transmission systems. In the paper we have given an overview of the mathematical description of PMD. We have demonstrated the deleterious effect of PMD on high bit-rates in various simulations preformed by the computer program FiberProp we developed. The special attention is given to the impact of PMD on solitons, which had been introduced as a solution to compensate the group velocity dispersion problem. It is shown that they can be used also for mitigation of PMD. The solution to the PMD problem is either to install new fibers with low PMD, or to try to compensate PMD on already installed fibers. Some principles of PMD compensation for various applications are discussed in the paper.
6 citations
01 Jan 2004
6 citations
12 May 2004
TL;DR: In this paper, the spectral-domain approach to the analysis of the spherical antenna arrays is studied, where the original three-dimensional problem is reduced to a spectrum of one-dimensional problems.
Abstract: The spectral-domain approach to the analysis of the spherical antenna arrays is studied in the paper. The main advantage of transforming the original problem in the spectral domain is that the original three-dimensional problem is reduced to a spectrum of one-dimensional problems. Therefore, the Green's functions needed for applying the moment method, as well as the elements of the moment method matrix, can be determined in the spectral domain. The main disadvantage lies in numerical problems appearing when the structures with large radii are analyzed. In order to avoid numerical problems a modified vector-Legendre transformation and normalized Legendre polynomials are defined and applied to the solution procedure. The abilities of the method are demonstrated on the analysis of the microstrip patch antennas and waveguide antennas mounted on the spherical supporting structure.
3 citations
12 May 2004
TL;DR: In this paper, boundary conditions in finite differences numerical model of pulse propagation along the optical link are studied in the case where fiber nonlinearities are also involved and the description and comparison of zero boundary conditions, absorbing boundary conditions (ABC), and transparent boundary condition (TBC) are given.
Abstract: Boundary conditions in finite differences numerical model of pulse propagation along the optical link are studied in the paper. The description and comparison of zero boundary conditions (ZBC), absorbing boundary conditions (ABC) and transparent boundary conditions (TBC) are given. Several simulation examples are listed illustrating the fact that ABC should be chosen as the most accurate solution for more demanding optical links where fiber nonlinearities are also involved.
2 citations
01 Jan 2004
TL;DR: Using the criteria of best accuracy and least computational time needed, finite-differences for optical fiber modeling are chosen and it is concluded that transparent boundary conditions (TBC) take less computational time than absorbing Boundary conditions (ABC).
Abstract: In the paper we describe possible numerical models for modeling optical link components. Using the criteria of best accuracy and least computational time needed we have chosen finite-differences for optical fiber modeling. We also analyzed the use of various boundary conditions in numerical model and concluded that transparent boundary conditions (TBC) take less computational time than absorbing boundary conditions (ABC). Several simulation examples are given to illustrate the abilities of the simulation program FiberProp we developed.
01 Jan 2004
TL;DR: In this paper, the authors investigated negative refraction by measurement of lateral displacement of the beam refracted at the slab made out of "backward-wave" meta-material, which was based on parallel plate waveguide loaded with double ring resonators.
Abstract: This paper reports investigation of negative refraction by measurement of lateral displacement of the beam refracted at the slab made out of 'backward-wave' meta-material. The meta-material was based on parallel plate waveguide loaded with double ring resonators. The slab was illuminated by 8 GHz microwave beam at several different angles of incidence. The beam was generated by horn antenna and location of the maximum of refracted beam was measured by an open rectangular waveguide. It was found that maximum always lied on the same side of the normal, where the incoming beam impinged the slab. This result is consisted with the theory and it proves phenomenon of negative refraction.