2009/2

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    SPICE Model of Memristor with Nonlinear Dopant Drift
    (Společnost pro radioelektronické inženýrství, 2009-06) Biolek, Zdenek; Biolek, Dalibor; Biolkova, Viera
    A mathematical model of the prototype of memristor, manufactured in 2008 in Hewlett-Packard Labs, is described in the paper. It is shown that the hitherto published approaches to the modeling of boundary conditions need not conform with the requirements for the behavior of a practical circuit element. The described SPICE model of the memristor is thus constructed as an open model, enabling additional modifications of non-linear boundary conditions. Its functionality is illustrated on computer simulations.
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    Distribution of Video-on-Demand Service over Cable Television Networks
    (Společnost pro radioelektronické inženýrství, 2009-06) Jordanova, Lidia T.; Nenkov, Jordan I.
    The paper deals with investigations carried out to increase the effectiveness of video-on-demand (VoD) systems when cable television networks are used. A comparative analysis of the existing VoD architectures is made with respect to the equipment cost and the traffic load over the central transport network. Through statistical studies the main characteristics of a particular hybrid VoD are determined (such as twenty-four-hour distribution of the video traffic, average inter-arrival time of the VoD requests, average duration of video streams demanded, movies distribution according to the subscribers’ preferences). An algorithm for the videocontent flexible distribution among the distribution hubs is suggested. Thus a higher effectiveness of the system is achieved without significantly increasing the equipment cost.
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    Influence of EBG Structures on the Far-Field Pattern of Patch Antennas
    (Společnost pro radioelektronické inženýrství, 2009-06) Horak, Jiri; Raida, Zbynek
    In this paper, the influence of the EBG structures on the far-field pattern of patch antennas is investigated. As a reference model, a conventional rectangular patch antenna on a high-permittivity substrate is used. The reference model is consequently equipped by an EBG substrate (instead of the conventional one), and by an EBG cover (so called EBG superstrate). The changes in the farfield radiation patterns are discussed. In the second part of the paper, the substrate is perturbed by two different EBG structures designed for the coverage of two operation bands.
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    Wireless Sensor Networks: VAN-Project Perspectives
    (Společnost pro radioelektronické inženýrství, 2009-06) Lakkundi, Vishwas; Kraetzig, Marko
    The emergence of wireless sensor networks and their potential for a multitude of novel applications, especially in the industrial automation domain, are noteworthy. This paper presents research and development perspectives on wireless sensor networks from the Virtual Automation Networks project in terms of prototype development and coexistence with other chosen wireless technologies. The project-specific design and specification aspects, implementation and integration issues, and coexistence tests, measurements and results are covered in detail. The paper illustrates the successful integration of wireless sensor networks into the overall prototype and shows that they can coexist with other wireless technologies.
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    Compensation of Wall Effect for Through Wall Tracking of Moving Targets
    (Společnost pro radioelektronické inženýrství, 2009-06) Rovnakova, Jana; Kocur, Dusan
    Through wall tracking of moving targets is of interest for rescue, surveillance and security operations. A useful method applies an ultra-wideband radar approach for this purpose since electromagnetic waves in the lower GHz- range penetrate most common building materials, such as bricks, wood, dry walls, concrete and reinforced concrete. However in consequence of a wall effect, estimated target track can be considerably spatially shifted and distorted. In the paper, two different methods for compensation of this ef- fect are described. Their effectiveness is evaluated at syn- thetic as well as real radar data. Obtained results prove that proposed novel approach reach the best outcomes.