2006/2

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Now showing 1 - 5 of 9
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    Methodology of Neural Design: Applications in Microwave Engineering
    (Společnost pro radioelektronické inženýrství, 2006-06) Pomenka, Petr; Raida, Zbynek
    In the paper, an original methodology for the automatic creation of neural models of microwave structures is proposed and verified. Following the methodology, neural models of the prescribed accuracy are built within the minimum CPU time. Validity of the proposed methodology is verified by developing neural models of selected microwave structures. Functionality of neural models is verified in a design - a neural model is joined with a genetic algorithm to find a global minimum of a formulated objective function. The objective function is minimized using different versions of genetic algorithms, and their mutual combinations. The verified methodology of the automated creation of accurate neural models of microwave structures, and their association with global optimization routines are the most important original features of the paper.
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    Quad-Band U-Slot Antenna for Mobile Applications
    (Společnost pro radioelektronické inženýrství, 2006-06) Palmero, Eduardo de las Heras; Raida, Zbynek; Ruiz, Roberto Lamadrid
    In this paper, two different planar quad-band antennas are designed, modeled, fabricated and measured. Subsequently, the antennas are redesigned using an electromagnetic band gap substrate (EBG). Those new planar antennas operate in four frequency bands: 900 MHz, 1 800 MHz (both GSM), 1 900 MHz (USA) and 2 400 to 2 500 MHz (Bluetooth) The antenna has four narrow U-shaped slots etched to the patch. Using software, CST Microwave Studio [1], Zeland IE3D [2], and FEMLAB [3], simulations have been carried out to investigate the antenna\'s performance and characteristics. The antennas designed have been also built and measured to compare the real results with those obtained from the simulations.
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    Difference Equations with Forward and Backward Differences and Their Usage in Digital Signal Processor Algorithms
    (Společnost pro radioelektronické inženýrství, 2006-06) Smekal, Zdenek
    In the paper the relation is given between linear difference equations with constant coefficients those obtained via the application of forward and backward differences. Relation is also established between input-output difference equations and state-space difference equations, which define the state of inner quantities of a discrete system. In conclusion, the state-space representation of a discrete system is given, which is suitable for implementing a discrete system in the microprocessor and digital signal processor. The resultant solution consists of the response to input signal and the response to non-zero initial conditions.
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    Error Concealment using Neural Networks for Block-Based Image Coding
    (Společnost pro radioelektronické inženýrství, 2006-06) Pavlovicova, Jarmila; Oravec, Milos; Polec, Jaroslav; Kelesi, Milan; Mokos, Martin
    In this paper, a novel adaptive error concealment (EC) algorithm, which lowers the requirements for channel coding, is proposed. It conceals errors in block-based image coding systems by using neural network. In this proposed algorithm, only the intra-frame information is used for reconstruction of the image with separated damaged blocks. The information of pixels surrounding a damaged block is used to recover the errors using the neural network models. Computer simulation results show that the visual quality and the MSE evaluation of a reconstructed image are significantly improved using the proposed EC algorithm. We propose also a simple non-neural approach for comparison.
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    Statistical CAC Methods in ATM
    (Společnost pro radioelektronické inženýrství, 2006-06) Baronak, Ivan; Kvackaj, Peter
    Admission control is a very useful tool for a network operator. It enables effective link utilization with QoS guaranty. Without doubts, CAC function will be important part in evolution of next generation networks. The question, how to choose suitable CAC method as admission control, is crucial for effective exploitation of CAC function. In this paper, we compare three statistical CAC methods providing their suitability as control for specific traffic: Method of Effective Bandwidth, Diffusion Approximation Method and Gaussian Approximation Method.