No description available.

No description available.

Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 1995. / "December 1995." Thesis advisor(s): R. Clark Robertson. Includes bibliographical references. Also available online.

Recent developments in digital communications at microwave frequencies have revealed that local oscillator phase noise is often a factor in the bit error rate (BER) analysis. Digital signals transported across microwave radio links acquire waveform jitter from local oscillator phase noise. As jitter increases so does BER. The main goals of the investigations described in this dissertation are to demonstrate the feasibility of determining rms jitter from measured phase noise and to develop mathematical models to describe how local oscillator phase noise is added to an information signal passing through a radio link. The first goal of estimating jitter from phase noise data has many applications. An obvious use is to specify the phase noise performance of a local oscillator for a given jitter specification which in turn may be specified for a desired BER level. A less obvious application is the ability to estimate the jitter of a microwave or millimeter wave signal based on measured phase noise. At these high frequencies it is often impractical or impossible to measure jitter directly due to performance limitations of time domain equipment such as the digital sampling oscilloscopes (DSO) which are typically limited to about 22 GHz. Conversely spectrum analysis techniques are well developed that allow accurate phase noise measurements to be performed well beyond 100 GHz. Experiments which validate the known relation between an oscillator's single sideband phase noise and associated mean square jitter [8, 28] are presented. Test equipment was developed to allow the addition of phase noise in a controlled manner to a clean reference signal which for practical purposes has no inherent jitter. By performing the experiments at the relatively low frequency of 33.333 MHz both the phase noise and jitter could be measured easily. Comparing the rms jitter predicted from phase noise data to direct measurement with a Digital Sampling Oscilloscope determined that the relation gave typically less than 14% error with a worst case disagreement of 24%. The experiment had an estimated uncertainty of �� 17%. This level of agreement is acceptable for many BER applications, which often specify jitter to an order of magnitude. The second goal of the research was to develop a model which describes how the phase noise of transmitter and receiver local oscillators add to an information signal carried over a communications link. It is shown that this added phase noise can in principle be eliminated in a double sideband communications system when the relative phase difference between the two local oscillators is synchronized to N��, where N is any integer. Experiments were performed which validated the predicted results. It was found that using real components allowed a 24 dB reduction added phase noise when compared to the case when no synchronization was used. A practical circuit is proposed to implement the technique in a practical manner for real radio systems. A final area of research presented phase noise measurements for a Gunn diode microwave integrated circuit (MIC) voltage controlled oscillator (VCO) in the 18 GHz region. The single sideband phase noise ratio of -96 dBc/Hz at 100 kHz offset frequency was significantly better than current published data for MESFET, HBT, and PHEMT VCOs at similar frequencies. These results are important in the area of digital radios, since improved phase noise allows higher data rates and reduces adjacent channel power. / Graduation date: 1999

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Speech; noise reduction; spectral subtraction; hands-free; beamforming. Includes bibliographical references (p. 171-189).

No description available.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.136-139).

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Mar. 18, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Medical Physics, Department of Physics, University of Alberta. Includes bibliographical references.

Decameter radiation was first observed from Jupiter by Burke and Franklin (JGR 60, 213, 1955). In 1964 Bigg (Nature, 203, 1008, (1964)) found that 1o exerted a profound effect on the radiation. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency. Intro., p. 1. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency (for a review see eg. Warwick, Space Sci. Rev. &" 841 (1967)). More recent work centred around the question of how 10 modulates the emission (see the article of Carr and Gulkis (Annual Review of Astronomy and Astrophysics Vol 8 (1970)) for a detailed review).

Thesis (PhD) -- Stellenbosch University, 2004. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: The radio noise (RN) performance of an AC high voltage transmission line is a determining factor when accessing the reliability of the design. The conducted RN level across the terminals of a PLC receiver, used in the teleprotection system of the line, is of particular concern. In this dissertation, existing empirical and semi-analytical RN prediction methods are evaluated by comparing the conducted RN levels of four South African lines to the predicted levels. Existing RN measurement protocols are consolidated and a new RN measurement protocol is proposed for the comparison. A prediction methodology, based on the EdF, EPRI and IREQ semi-analytical methods, is formulated. The semi-analytical methods are not able to accurately predict the variation of the conducted RN with frequency in the PLC band, nor are they able to predict the RN performance of short lines. A wideband excitation function, which considers the statistical characteristics of the measured RN pulse train, is therefore proposed in this dissertation. Having investigated the extraction of this excitation function from ESKOM’s Megawatt Park corona cage, it is concluded that a small corona cage is required. The design of a small cage is presented and the extraction of the excitation function is described. Attention is given to assessing the effect of changes in space charge distributions. The effect of space charge collision with an insulated cage on the extracted pulse parameters is linear, provided space charge diffusion is negligible. The onset streamer, positive streamer and negative streamer corona modes were identified as the only modes with measurable RN in the frequency regime 150 kHz to 30 MHz. Formulas are derived for the prediction of the inception gradients for these modes. The RN performance of an ACSR Hare conductor is extracted from the small cage. The RN performance of the Acacia-Koeberg line is also approximated in the PLC band. The dissertation concludes that the proposed wideband excitation function method is capable of accurately predicting the variation of RN levels with frequency. It can also be used to predict the RN performance of short line sections, as well as the relationship between RMS, QP and average RN levels from a transmission line. / AFRIKAANSE OPSOMMING: Die korona-werkverrigting van ‘n WS hoogspanningstransmissielyn het belangrike gevolge vir die betroubaarheid van die ontwerp van die lyn. Die geleide radioruis (RR) vlak op die kraglyndragolf kommunikasie sisteem, wat vir tele-beveiliging gebruik word, is veral van belang. In hierdie werkstuk word bestaande metodes gebruik om die korona-werkverrigting te bepaal en dan met gemete waardes van vier Suid Afrikaanse lyne te vergelyk. Bestaande RR meetmetodes word saamgevat en ‘n nuwe metingsprotokol word voorgestel om resultate te vergelyk. Na aanleiding van hierdie vergelykings word ‘n tegniek ontwikkel om die RR van ‘n lyn te voorspel. Hierdie tegniek gebruik die EdF, EPRI en IREQ metodes. Die voorgestelde tegniek kan nie die verandering van die RR met frekwensie bepaal nie. Dit kan ook nie die RR van kort lyne bepaal nie. ‘n Wyeband RR bron word dus voorgestel. Nadat ESKOM se Megawatt Park korona-kou ondersoek is, is die gevolgtrekking gemaak dat ‘n klein koronakou die nodige wyeband RR bron sal voorsien. Ruimtelading bots met die klein korona-kou. Die effek van hierdie botsings op die pulsparameters is lineer indien ladingsdiffusie nie plaasvind nie. Die aanvangs, positiewe en negatiewe kanaalontladings (“streamers”) is identifiseer as die enigste koronamodusse wat RR veroorsaak tussen 150 kHz en 30 MHz. Die spanning waarby hierdie modusse voorkom, is bepaal. Die korona-werkverrigting van ‘n “ACSR Hare” geleier is bepaal. Die korona-werkverrigting van die Acacia-Koeberg transmissie lyn is ook gekwantifiseer by die kraglyn-dragolf kommunikasie frekwensies. Die wyebandbron metode kan die verandering in RR met frekwensie goed voorspel. Die nuwe metode kan ook gebruik word om die RR van kort lyne te bepaal, asook die verband tussen RMS, QP en gemiddelde RR vlakke.