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Wireless systems incorporating full-diversity single-symbol decodable space-time block codes: performance evaluations and developmentsLee, Hoo-jin, 1973- 29 August 2008 (has links)
Not available
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Pilot-symbol-aided techniques for spectrally efficient signals in multipath-fading channels劉慶強, Lau, Hing-keung. January 1997 (has links)
published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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Σχεδίαση διάταξης πολυκαναλικού πομπού για γραμμές χαμηλής τάσης εντός κτηρίουΑναγνωστοπούλου, Ζαφειρία 18 June 2009 (has links)
Η τεράστια τεχνολογική ανάπτυξη που χαρακτηρίζει την εποχή µας και το πλήθος
των εφαρµογών που αυτή συνεπάγεται ορίζει επιτακτική την ψηφιακή µετάδοση δεδοµένων
σε µεγάλες αποστάσεις και µε εγκυρότητα. Οι απαιτήσεις αυτές οδήγησαν στην ανάπτυξη
της τεχνικής OFDM (Orthogonal frequency-division multiplexing), µίας από της καλύτερες
τεχνικές πολυπλεξίας. Θέµα της διπλωµατικής µου εργασίας είναι η ανάπτυξη ενός
πολυκαναλικού ποµπού (OFDM transmitter) για γραµµές χαµηλής τάσης εντός κτηρίου.
Συγκεκριµένα στο πρώτο µέρος της εργασίας παρουσιάζεται η θεωρητική βάση στην
οποία στηρίζεται η σχεδίαση και υλοποίηση του ποµπού. ∆ίνεται έµφαση στην επεξήγηση
της έννοιας «πολυκαναλικό» καθώς επίσης και γιατί ένας τέτοιου είδους ποµπός θα είναι
χρήσιµος ως µέρος ενός ποµποδέκτη για µεταφορά δεδοµένων εντός κτηρίου.
Στη συνέχεια της εργασίας παρουσιάζεται βήµα προς βήµα η σχεδίαση και ανάπτυξη
του µοντέλου προσοµοίωσης του πολυκαναλικού ποµπού µε χρήση του εργαλείου
Matlab/Simulink. Αρχικά παρουσιάζονται οι διάφοροι παράµετροι του ποµπού όπως ο
αριθµός των υποκαναλιών του συστήµατος, ο µέγιστος αριθµός των bit που θα µεταδίδει
κάθε υποκανάλι και η διαµόρφωση που θα εφαρµόζεται σε κάθε υποκανάλι. Στη συνέχεια
παρουσιάζεται σχηµατικά η διαδικασία δηµιουργίας διαµορφωµένων συµβόλων και η
δειγµατοληψία αυτών µε σκοπό τη δηµιουργία δειγµάτων προς µετάδοση. Το συγκεκριµένο
µοντέλο περιλαµβάνει όλες τις απαραίτητες λειτουργίες που απαιτούνται για τη δηµιουργία,
κωδικοποίηση και µεταφορά δεδοµένων σύµφωνα µε την OFDM τεχνική, λαµβάνοντας
υπόψην τα χρονικώς µεταβαλλόµενα χαρακτηριστικά του καναλιού µετάδοσης. Επί πλέον,
δίνεται πλήρης επεξήγηση για τον σχεδιασµό κάθε υποσυστήµατος που χρησιµοποιήθηκε για
την ολοκλήρωση του µοντέλου.
Η παρουσίαση ολοκληρώνεται µε την παράθεση και επεξήγηση των αποτελεσµάτων
των προσοµοιώσεων τα οποία επιβεβαιώνουν την ορθότητα λειτουργίας του συστήµατος
που υλοποιήθηκε. / -
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A proportional timing generator for measuring intermodulation product distortion on television transposers.Bouwer, Paul Frederick. January 1989 (has links)
Broadcasting authorities presently measure intermodulation distortion by
applying a three tone simulation of a composite video and sound signal to the
transposer and then measuring the relative amplitude of the major in-band
intermodulation product (nominally at vision carrier frequency plus 1,57 MHz in
the 625 line I/PAL System) on a spectrum analyser. This method is slow and
requires a skilful operator to achieve repeatable results. Furthermore it tests the
common RF amplification equipment at one luminance level and one
chrominance level and therefore does not subject the transposer equipment to
operation over its full range.
A new sampling measurement technique has been proposed which overcomes
all these problems by selectively mixing, while transmitting a colour bar test
pattern, the demodulated output video signal of the frequency transposer with
a pulse train coinciding with a particular colour. This thesis describes the
design of a very stable proportional timing generator and its application to the
measurement of intermodulation distortion on frequency transposers.
The timing generator, which locks automatically onto the video signal and
produces narrow sampling pulses which coincide accurately with a particular
section of each line over a 50°C temperature range, is applicable to all PAL and
NTSC TV Systems. / Thesis (Ph.D.)-University of Natal, Durban, 1989.
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Statistics on 10 GHz attenuation due to precipitation in Montreal and Alberta.Inkster, Don Robert January 1973 (has links)
No description available.
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Adaptive techniques with cross-layer design for multimedia transmission.Vieira, Ricardo. January 2013 (has links)
Wireless communication is a rapidly growing field with many of its aspects undergoing
constant enhancement. The use of cross-layer design (CLD) in current technologies has
improved system performance in terms of Quality-of-Services (QoS) guarantees. While
multimedia transmission is difficult to achieve, CLD is capable of incorporating techniques
to achieve multimedia transmission without high complexity. Many systems have
incorporated some form of adaptive transmission when using a cross-layer design approach.
Various challenges must be overcome when transmitting multimedia traffic; the main
challenge being that each traffic type, namely voice; image; and data, have their own
transmission QoS; delay; Symbol Error Rate (SER); throughput; and jitter requirements.
Recently cross-layer design has been proposed to exchange information between different
layers to optimize the overall system performance. Current literature has shown that the
application layer and physical layer can be used to adequately transmit multimedia over
fading channels. Using Reed-Solomon coding at the application layer and Rate Adaption at
the physical layer allows each media type to achieve its QoS requirement whilst being able
to transmit the different media within a single packet.
The following dissertation therefore strives to improve traffic through-put by introducing an
unconventional rate adaption scheme and by using power adaption to achieve Symbol Error
Rate (SER) QoS in multimedia transmission.
Firstly, we introduce a system which modulates two separate sets of information with
different modulation schemes. These two information sets are then concatenated and
transmitted across the fading channel. The receiver uses a technique called Blind Detection
to detect the modulation schemes used and then demodulates the information sets
accordingly. The system uses an application layer that encodes each media type such that
their QoS, in terms of SER, is achieved. Simulated results show an increase in spectral
efficiency and the system achieves the required Symbol Error Rate constraint at lower Signal
to Noise Ratio (SNR) values.
The second approach involves adapting the input power to the system rather than adapting
the modulation scheme. The two power adaptive schemes that are discussed are Water-
Filling and Channel Inversion. Channel Inversion allows the SER requirement to be
maintained for low SNR values, which is not possible with Rate Adaption. Furthermore, the
system uses an application layer to encode each media type such that their QoS is achieved.
Simulated results using this design show an improvement in through-put and the system
achieves the SER constraint at lower SNR values. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.
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Design, implementation, and testing of a software interface between the AN/SPS-65(V)1 radar and the SRC-6E reconfigurable computer /Guthrie, Thomas G. January 2005 (has links) (PDF)
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Douglas J. Fouts. Includes bibliographical references (p. 61). Also available online.
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Synthesizer modulation for wideband FM generationSnyman, A. (Anton) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The high performance of present digital phase-locked loops makes it
the preferred choice for the generation of stable, low noise, tunable local
oscillators in wireless communications applications. Most transmitters
use superheterodyn techniques for up-conversion of the modulated signal
to the required transmission frequency. Another technique is to inject the
modulation signal into a phase-locked loop and consequently generate a
frequency modulated signal directly at the transmission frequency.
The aim of this study is to obtain a synthesizer configuration for the
effective generation of wideband FM, considering both passive and active
loop filters. The selection is based on synthesizer output signal quality,
settling time and loop response to the modulation signal. / AFRIKAANSE OPSOMMING: Die hoe werksverrigting van fase-sluit lusse maak dit die verkiesde keuse
vir die generasie van stabiele, lae ruis, verstelbare ossillators vir draadlose
kommunikasie toepassings. Meeste senders gebruik "superheterodyn"
tegnieke vir die op-menging van die gemoduleerde sein na die verlangde
uitsaai frekwensie. 'n Ander tegniek is om die modulasie sein in
'n fase-sluit Ius te voer en so doende 'n gemoduleerde sein direk by die
transmissie frekwensie te genereer.
Die doel van hierdie studie is om 'n sintetiseerder konfigurasie te verkry
vir die effektiewe opwekking van 'n wyeband FM sein, deur beide passiewe
en aktiewe Ius filters in konsiderasie te neem. Die seleksie geskiet gebaseer
op sintetiseerder uittree sein kwaliteit, sluit tyd en Ius gedrag as gevolg
van die modulasie sein.
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Thermoelectric cooling for microwave transmitters located at remote sitesPietersen, Richard Gordon January 1992 (has links)
Thesis (MDiploma (Mechanical Engineering))--Cape Technikon, 1992. / An investigation into the use of thermoelectric cooling
energised by photovoltaic (PV) panels for removing sensible
heat from electronic telecommunications equipment.
The thermoelectric cooler consists of a solid-state heat pump
which operates on the principle of the Peltier effect. The
thermoelectric device transfers heat through a cold sink to
ambient outside air via a hot sink.
A major prerequisite was that the system should be selfsufficient
in terms of power because the sites for the
microwave transmitters are often remote. Solar power was
the only alternative source of energy and the cooler was
designed to accept direct current from PV panels which are
usually used to power transmitters on distant locations. The
cooling device had to be reliable, virtually maintenance-free
and simple to repair.
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Técnicas combinadas de autoalimentação e reuso de comprimento de onda em transmissores refletivos para redes WDM-PON / Combined self-seeding and wavelength reuse for reflective transmistters in WDM-PONUlysses Rondina Duarte 06 March 2015 (has links)
Transmissores agnósticos em comprimento de onda colorless [1], isto é, transmissores que não estão restritos à operação em um único comprimento de onda, são considerados como um dos pré-requisitos para os projetos de redes ópticas passivas baseadas na multiplexação por divisão em comprimento de onda Wavelength Division Multiplexing Passive Optical Network. Esta configuração reduz consideravelmente os custos operacionais e de instalação da rede WDM-PON, uma vez que um único tipo de transmissor pode ser usado em qualquer terminal de assinante, independentemente dos comprimentos de onda pré-estabelecidos para os usuários em questão. Entretanto, a possibilidade de aumento do número de usuários e da capacidade de transmissão agregada, com poucas modificações na estrutura da rede WDM-PON, garantindo uma melhor relação custo-benefício, são questões também essenciais no projeto de sistemas multi-comprimento de onda.Tendo em vista o panoramo exposto, neste trabalho é proposta uma nova topologia de reuso de portadora óptica para redes WDM-PON, a qual combina sinais autoalimentados e remodulação óptica no domínio da intensidade, visando o atendimento das premissas tecnológicas para cenários de nova geração. Como metodologia, investigações experimentais são conduzidas em termos de caracterizações ópticas em função de vários parâmetros e avaliações sistêmicas em taxas simétricas de 1,25 Gb/s, no âmbito de redes de acesso e acesso estendido. Utilizam-se transmissores colorless do tipo amplificadores ópticos semicondutores refletivos e fontes ópticas banda larga baseadas em emissão espontânea amplificada, de forma a garantir a simplificação dos terminais dos usuários. Adicionalmente, são realizadas análises comparativas entre essa proposta frente aos trabalhos encontrados na literatura técnica, quando possível, em termos de custos operacionais, desempenho sistêmico e viabilidade de expansão para cenários a taxas simétricas de 10 Gb/s. De acordo com os resultados obtidos, acredita-se que essa topologia possa ser expandida para cenários de até 10 Gb/s com o uso de técnicas apropriadas de apagamento de portadora, mantendo a melhor relação custo-beneficio para sistemas de remodulação no domínio da intensidade. / Wavelength agnostic (colorless) transmitters [1], i.e, transmitters which are not fixed to a specific wavelength operation, are regarded as one of the essential keys for the designing of wavelength division multiplexing passive optical networks (WDM-PONs). The use of colorless transceiver leads to a reduction in the mainentence cost of the network, once the same basic optoelectronic hardware can be employed to provide any wavelength required by a specific optical network termination (ONT). However, the possibility of a graceful increase on the number of ONTs and transmission capacity offered by the network, with no disruptive changes in the WDM-PON infra-structure, while keeping a cost-effective topology, are also attractive features in the design of future access networks. In this context, a novel wavelength-reuse topology for WDMPON is proposed in this work. The wavelength-sharing technique is based on combined self-seeded and remodulated signals in the intensity domain, in order to comply with the technology requierements for next generation networks. Experimental analysis are carried out in respect to optical characterization and system evaluation on symmetric rates of 1.25 Gb/s, aiming both short reach and extended reach scenarios. Reflective semicondutor optical amplifiers and broadband light sources based on amplified spontaneous emission are used as colorless transceivers in order to guarantee a costeffective ONT configuration. Also, comparative analyses between this proposal and works found in the technical literatural are established in terms of maintenance costs, system performance and feasibility of expansion to symmetric 10 Gb/s scenario. According to the results, we believe that network could be expanded to symmetric 10 Gb/s scenario with the development of proper erasure technique, while keeping the best cost-effective configuration of intensity-remodulated systems.
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