2008/4

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    Eyelid Localization for Iris Identification
    (Společnost pro radioelektronické inženýrství, 2008-12) Adam, Mathieu; Rossant, Florence; Amiel, Frederic; Mikovikova, Beata; Ea, Thomas
    This article presents a new eyelid localization algorithm based on a parabolic curve fitting. To deal with eyelashes, low contrast or false detection due to iris texture, we propose a two steps algorithm. First, possible edge candidates are selected by applying edge detection on a restricted area inside the iris. Then, a gradient maximization is applied along every parabola, on a larger area, to refine parameters and select the best one. Experiments have been conducted on a database of 151 iris that have been manually segmented. The performance evaluation is carried out by comparing the segmented images obtained by the proposed method with the manual segmentation. The results are satisfactory in more than 90% of the cases.
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    Slotted PIFA for Mobile Communication Devices
    (Společnost pro radioelektronické inženýrství, 2008-12) Bonefacic, Davor; Rapinac, Bojan; Bartolic, Juraj
    Slotted PIFA with capacitive loading for operation in the 880 / 960 MHz band is presented. The PIFA is intended for mobile terminals in GSM mobile communication network. The antenna is placed on a ground plane with dimensions of an average handheld device. It is optimized by using electromagnetic simulator and a prototype is manufactured. Calculated and measured results agree very well. Input impedance matching with SWR < 3 in the whole band was achieved. Maximum gain of 3.2 dBi is measured. Preliminary studies of the influence of the user\'s head and hand on the antenna characteristics have been performed.
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    Optimization of Micro Strip Array Antennas Using Hybrid Particle Swarm Optimizer with Breeding and Subpopulation for Maximum Side-Lobe Reduction
    (Společnost pro radioelektronické inženýrství, 2008-12) Chaker, Hichem; Meriah, Sidi Mohamed; Bendimerad, Fethi Tarik
    In this paper, a technique based on hybrid particle swarm optimiser with breeding and subpopulation is presented for optimal design of reconfigurable dual-beam linear array antennas and planar arrays. In the amplitudephase synthesis, the design of a reconfigurable dual-pattern antenna array is based on finding a common amplitude distribution that can generate either a pencil or sector beam power pattern, when the phase distribution of the array is modified appropriately. The goal of this study is to introduce the hybrid model to the electromagnetic community and demonstrate its great potential in electromagnetic optimizations.
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    Parametric Study of Mushroom-like and Planar Periodic Structures in Terms of Simultaneous AMC and EBG Properties
    (Společnost pro radioelektronické inženýrství, 2008-12) Kovacs, Peter; Raida, Zbynek; Martinez-Vazquez, Marta
    In the paper, the parametric analysis of a mushroom-like and a planar metallo-dielectric periodic structure with square unit cell and metallic patch is presented. First, the angular stability for different unit cell settings was studied. Second, restrictions for simultaneous behavior as artificial magnetic conductor (AMC) and electromagnetic band gap (EBG) are briefly discussed. Finally, main differences between the mushroom-like and the planar structure are specified and conclusions are formulated.
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    The Time Difference of Arrival Estimation of Wi-Fi Signals
    (Společnost pro radioelektronické inženýrství, 2008-12) Nemec, Zdenek; Bezousek, Pavel
    The papers deals with a modeling of a Time- Difference of Arrival system for a subscriber station localization, based on the 802.11 standard wireless network. In the case of severe multipath effects the standard TDOA estimation methods, based on correlation of signals, received by conveniently displaced receiving stations show large errors. Thus, a new algorithm is proposed using received signals decomposition to a set of delayed replicas. This represents a linear estimation of reflected signals amplitudes. The described method leads to a better estimation of time differences of the signals, propagating on the direct paths between the emitter and the receiving stations.