2008/2

Browse

Recent Submissions

Now showing 1 - 5 of 22
  • Thumbnail Image
    Item
    MIMO Capacity Estimation at 2 GHz with a Ray Model in Urban Cellular Environment
    (Společnost pro radioelektronické inženýrství, 2008-06) Vergerio, Sophie; Rossi, Jean-Pierre; Sabouroux, Pierre
    MIMO technology promises a linear increase of capacity in function of the minimum antenna number at the transmitter and at the receiver. In order to test if these performances can be actually met in mobile communications, we propose here a study of MIMO (Multiple Input Multiple Output) capacity in urban cellular environment at 2 GHz with a help of an efficient ray propagation model. We have tested different types of base station antennas (vertically or ±45° polarized) and two different types of mobile. Capacity is found to significantly increase between SISO (Single Input Single Output) and MIMO systems, but less than usually expected. We show that return and coupling losses as low as 10% can also reduce significantly the capacity. On the other hand, we study the influence of the way to take into account received power level on the MIMO capacity estimation.
  • Thumbnail Image
    Item
    User Interaction with Inverted-F Antennas Integrated into Laptop PCMCIA Cards
    (Společnost pro radioelektronické inženýrství, 2008-06) Guterman, Jerzy; Moreira, Antonio A.; Peixeiro, Custodio; Rahmat-Samii, Yahya
    This paper evaluates the overall laptop integration effects on the performance of commercial 2.4 GHz Inverted-F antennas built into PCMCIA cards. A generic laptop model is used to represent the antenna housing effects while an anatomical shape homogenous human model is used to estimate the electromagnetic interaction between the antenna and the user. The antenna performance is evaluated for different card locations in terms of reflection coefficient, far-field gain pattern and radiation efficiency. The human exposure to EM radiation is analyzed in terms of Specific Absorption Rate.
  • Thumbnail Image
    Item
    Contactless Area Measurement (Contactless Planimeter)
    (Společnost pro radioelektronické inženýrství, 2008-06) Ricny, Vaclav; Stancik, Petr
    The paper describes the designed hardware and software systems (so-called planimeters) for contactless measurement of areas (eventually geometric distances between two selected points) of planar projections of various objects. These systems operate on the principle of processing the video signal scanned by a digital camera (or TV camera).
  • Thumbnail Image
    Item
    Analysis of Highly Directive Cavity-Type Configurations Comprising of Low Profile Antennas Covered by Superstrates
    (Společnost pro radioelektronické inženýrství, 2008-06) Farahat, Nader; Mittra, Raj; Lugo, Katherine; Ma, Lai-Ching; Gomez, Rodney A.
    In this paper we present a technique for designing antenna/superstrate composites to produce enhanced directivities. As a first step, we study the underlying mechanism that governs the performance of theses antennas by studying the canonical problem of a line source in a rectangular waveguide. The above problem is solved by constructing the Green’s function corresponding to the line source in the rectangular guide, one of whose walls is partially reflecting, that is can leak electromagnetic energy into the space external to the guide. The Green’s function for this problem can be constructed by aggregating the multiple reflections from the two walls. Although the above model is only two-dimensional, we show that it can be used to predict the performance of antenna/superstrate composites. We demonstrate this by modeling several highly directive antennas and show that indeed the required characteristics of this type of antennas can be determined from the analysis of the cutoff behavior of the rectangular guide.
  • Thumbnail Image
    Item
    Local Positioning Services on IEEE 802.11 Networks
    (Společnost pro radioelektronické inženýrství, 2008-06) Vegni, Anna Maria; Di Nepi, Alessandro; Neri, Alessandro; Vegni, Claudio
    This paper deals with localization services in IEEE 802.11 networks, for indoor environment. The proposed solution processes the Time Of Arrival of location packets sent by a Mobile Terminal, that makes access in a IEEE 802.11 network. A set of Location Supporting Nodes and a Location Support Server composes an indoor location services architecture. A fully compatible IEEE 802.11 Localization Services protocol supporting data exchange related to both TOA measurement and processing is reported. Simulation results show the method efficiency in both IEEE 802.11 PCF and DCF modes. Assessment of the maximum number of users for which location services can be provided is also reported. Since high localization accuracy requires large bandwidth, a broadband antenna for LSN and LSS was designed. The related results are reported in the second part of the paper. The antenna works at 5.0 GHz (centre frequency) in broadband mode and is matched on the wireless operating frequencies with a percentage more than 8% (1:1.5 VSWR).