On the RLSA antenna optimum design for DBS reception

An optimal design for the RLSA (radial line slot array) antenna useful for DBS reception is presented. Classical geometries and structures given in the literature are first used. It is found that in some cases these are not suitable. So, optimization techniques by using the right objective functions have been applied. Two different methods were developed and three antennas were designed. Numerical results and comparisons with other similar antennas give the advantages of our design     

A unified formulation for Chebyshev and Legendre superdirective endfire array design

Contents A unified formulation for superdirective end-fire arrays by using Chebyshev and Legendre Polynomials and their maximum directivities as well as the corresponding efficiency index and theQ factor are found. Several examples show the simplicity of the formulation.

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Eine einheitliche Formulierung zum Design von Supergain-Längsstrahlern mit Tschebyscheff- und Legendre-Polynomen

Übersicht Es wird eine einheitliche Formulierung für Supergain-Längsstrahler mit Tschebyscheff- und Legendre-Polynomen vorgestellt. Die Strahlergruppen werden für unterschiedliche Kombinationen dieser Polynome angegeben, ebenso ihre optimalen Richtgewinne wie auch der dazugehörige Strahlungs- Wirkungsgrad in der Hauptrichtung und der GütefaktorQ. Einige Beispiele belegen die Einfachheit der Formulierung.

     

Design of radiation-emission measurements of an air-traffic surveillance radar

The current work presents the procedure of designing and carrying out measurements of radiation emission from an air-traffic surveillance radar. The system requirements are first given, and then the equipment used is described. The steps to determine the operating characteristics of the radar are specified in detail. The necessary methods for manual power measurements and calculations are next explained. Since the final measurement system was fully automated, its main features (topology, protocol of operation) are also given. Finally, some measurement results taken during the initial phase of system operation are presented and discussed.     

A reconstruction algorithm of electrical impedance tomography with optimal configuration of the driven electrodes

A reconstruction algorithm for electrical impedance tomography (EIT) is presented. The least-squares (LS) method is applied and a formulation similar to that of the perturbation method is found. The main difference from perturbation lies with the sensitivity matrix, which here is replaced by the Jacobian matrix, defined in terms of the partial derivatives of every sensing electrode pair voltage difference with respect to every element's conductivity. The mutual position between the active electrodes is chosen to give optimum sensitivity. The results shown that the algorithm presented here has a better convergence and needs fewer iterations than the perturbation method.     

A low-complexity 3-D geometric model for the description of CCI in cellular systems

In this paper, we propose a three-dimensional geometrically based stochastic model for the study of co-channel interference in cellular mobile systems. Exact analytical expressions for the statistics of the angle-of-arrival (AoA) of the interfering signals at the base station and the outage performance of a cellular network are derived. Simulated results show the merits of our proposal compared to the two-dimensional approach. The uplink AoA distribution statistics are examined in relation to cell size, antennas’ height and frequency reuse factor. Furthermore, the impact of base station antenna radiation pattern, beam tilting and cell sectorization on system performance is investigated.     

Characteristics of a rectangular waveguide containing a magnetized cylindrical ferrite post

A rigorous formulation of the scattering by a magnetized ferrite in a rectangular waveguide is presented. The EM field depends on the dimension, the frequency and the internal static magnetic field of the ferrite post. For some special values of the above quantitites the reflection or the transmission coefficient becomes equal to zero. These values give a family of filters and the results which follow explain their characteristics.     

A test lab for the performance analysis of TCP over ethernet LAN on windows operating system

A test laboratory for the performance analysis of the Transmission Control Protocol (TCP) and the teaching of its basic concepts is proposed. The laboratory environment is a small Ethernet local area network (LAN) with PCs running different versions of the Windows operating system (95/98/NT/2000). To support the Internet Protocol Version 6 (IPv6) for Windows and to improve flexibility, the Netperf TCP software tool has been modified. Based on the modified Netperf and a protocol analyzer, students perform traffic measurements on a real network. Various aspects of the Microsoft TCP implementation for Windows are discovered and clearly explained. The IPv6 for Windows 2000 is also examined, and comparisons with IPv4 are made.     

Synthesis method of series-fed microstrip antenna arrays

A method for non-uniformly spaced series-fed rectangular microstrip array synthesis is given. By this approach the problem of patch array design turns out to be slot array synthesis. The resulting equivalent configuration gives the necessary parameters for the microstrip array geometry. Applications on Taylor, Bayliss and shaped-beam patterns show the validity of the method     

A mode-matching technique for the study of circular and coaxialwaveguide discontinuities based on closed-form coupling integrals

A mode-matching scheme for the analysis of concentric circular and/or coaxial waveguide step discontinuities is proposed in this paper. An analytical evaluation of the involved coupling integrals for all possible discontinuities formed by any combination of a circular and a coaxial waveguide is performed. The originality mainly concerns the multimode excitation and scattering at a circular-to-coaxial waveguide step junction. Numerical results for a number of applications are compared against those of other techniques and/or measurements and are found to be in good agreement