2008/3
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Recent Submissions
Now showing 1 - 5 of 21
- ItemModeling of Microwave Semiconductor Diodes(Společnost pro radioelektronické inženýrství, 2008-09) Pokorny, Michal; Raida, ZbynekThe paper deals with the multi-physical mode-ling of microwave diodes. The electrostatic, drift-diffusion and thermal phenomena are considered in the physical model of the components. The basic semiconductor equati-ons are summarized, and modeling issues are discussed. The simulations of the Gunn Effect in transferred electron devices and the carrier injection effect in PIN diodes are investigated and discussed. The analysis was performed in COMSOL Multiphysics using the finite element method.
- ItemPreamble Design Problematic with 802.11a IEEE Standard (Minn’s Training Sequence Approach)(Společnost pro radioelektronické inženýrství, 2008-09) Oni, Romeo R. A.Generally OFDM systems use a predefined signal pattern, called preamble [2] [3], which helps the receiver to achieve a better signal detection (coarse, fine time synchronization) with the frequency offset and channel estimation. In most of the time having all these conditions fulfilled the receiver achieves relatively a good performance while keeping as low as possible the total consuming power and the BER (Bite Error Rate). This paper presents the results obtained while combining a part of the preamble [2] [3] and the Minn\'s training sequence. We have got interesting performance results comparable to those results obtained for the relatively new standard 802.16a.
- ItemBistatic and Multistatic Radar Systems(Společnost pro radioelektronické inženýrství, 2008-09) Bezousek, Pavel; Schejbal, VladimirRadar systems, based on bistatic radar concept attracted a substantial attention in the recent years. Passive coherent location systems using \"transmitters of opportunity\" like radio or TV broadcasters, GSM base stations, satellite communication and GNSS signals proved their potential in detection and tracking moving targets over a significant area. In this paper the multistatic location system with non-cooperative transmitters is described and various aspects of signal processing and signal parameters are discussed.
- ItemEstimating PSNR in High Definition H.264/AVC Video Sequences Using Artificial Neural Networks(Společnost pro radioelektronické inženýrství, 2008-09) Slanina, Martin; Ricny, VaclavThe paper presents a video quality metric designed for the H.264/AVC codec. The metric operates directly on the encoded H.264/AVC bit stream, parses the encoding parameters and processes them using an artificial neural network. The network is designed to estimate peak signal-to-noise ratios of the video sequence frames, thus enabling computation of full reference objective quality metric values without having the undistorted video material prior to encoding for comparison. We present the metric framework and test its performance for LDTV (low definition television) as well as HDTV (high definition television) video material.
- ItemDVB-T Digital Terrestrial Television Transmission over Fading Channels(Společnost pro radioelektronické inženýrství, 2008-09) Kratochvil, Tomas; Stukavec, RadimThe paper deals with the transmission of the digital television signal according to the DVB-T standard in SFN network over fading channels for the fixed reception. The laboratory transmission system for the real broadcasting based on R&S RF test and measuring equipments is presented including the transmission parameters setup. The results of broadcasting over Gausian, Ricean and Rayleigh channels and results of the echo impairments are presented and discussed with the theory and simulation results. The BER before and after Viterbi decoding and according to MER equal to S/N ratio in the channel from the constellation diagram were compared in all transmission experiments. Additional picture quality evaluation is presented using DVQL-W metric that monitors blockiness structures in MPEG-2 compressed pictures and gives notice of known \"cliff-off\" effect.