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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Analysis of shielded rectangular dielectric rod waveguide using mode matching

Wells, Colin G. January 2005 (has links)
The limit of current technology for mobile base station filters is the multimode filter, in which each cavity supports two (or possibly three) independent degenerate resonances. Shielded dielectric resonators with a rectangular cross-section are useful in this application. In the design of these filters, manufacturers are using software packages employing finite element or finite difference time domain techniques. However, for sufficient accuracy these procedures require large numbers of points or elements and can be very time consuming. Over the last decade research using the mode matching technique has been used to solve this kind of difficulty for various types of filter design and waveguide problems. In this thesis a mode matching method and computer program is developed to calculate the propagation coefficients and field patterns of the modes in a shielded rectangular dielectric rod waveguide. Propagating, complex, evanescent and backward wave modes are included and the work shows the presence of a dominant mode, and other fundamental modes, not previously identified. The effect of the shield proximity on the propagation characteristics and mode spectrum is investigated, together with the limitations on the accuracy of the mode matching method. In addition, the fields within the shielded rectangular dielectric rod waveguide, are used to calculate the attenuation coefficient of the dominant and fundamental modes. The influence on the attenuation coefficient of the proximity of the shield to the rod is also evaluated for these modes and limitations on accuracy are discussed. The calculated numerical results for the propagation and attenuation coefficient values are verified by measurement. The propagation coefficients results are typically within 2% of those measured. Verification of the attenuation coefficient results is achieved by comparing calculated and measured Q at the resonant frequencies of a number of shielded rectangular dielectric rod resonators. The difference between calculated and measured Q values is on average less than 4%. In the absence of a full solution of the shielded rectangular dielectric rod resonator, these results provide useful design information for this structure. In addition, the work reported in this thesis provides a basis for a full electromagnetic solution of this type of resonator. This would encompass the cubic dielectric resonator in a cubical cavity.
112

Mechatronische Systeme zur Pulsationsminderung hydrostatischer Verdrängereinheiten /

Goenechea, Eneko. January 2007 (has links)
Zugl.: Aachen, Techn. Hochsch., Diss., 2007.
113

Licht-Materie-Wechselwirkung in Festkörper-Nanostrukturen

Kahl, Matthias. January 2008 (has links)
Konstanz, Univ., Diss., 2008.
114

Nonlinear resonators for all-optical signal processing

Maitra, Ayan January 2007 (has links)
Zugl.: Karlsruhe, Univ., Diss., 2007 / Hergestellt on demand
115

Frequenzselektive Vibrationssensoren mit spannungsgesteuerter Resonanzabstimmung in Oberflächenmikromechanik

Wibbeler, Jürgen. Unknown Date (has links) (PDF)
Techn. Universiẗat, Diss., 2002--Chemnitz.
116

Aktiv verbesserte Aufsätze für Schallschutzwände

Koh, Hyo-In. Unknown Date (has links) (PDF)
Techn. Universiẗat, Diss., 2004--Berlin.
117

Optical control of single neutral atoms

Alt, Wolfgang. Unknown Date (has links) (PDF)
University, Diss., 2004--Bonn.
118

Quantum theory of amplifying random media

Viviescas Ramírez, Carlos Leonardo. Unknown Date (has links) (PDF)
Essen, University Diss., 2004--Duisburg.
119

A novel approach for designing integrated ultra low noise microwave wideband voltage controlled oscillators

Poddar, Ajay Kumar. Unknown Date (has links) (PDF)
Techn. University Diss., 2004--Berlin.
120

Rekenaargesteunde instelling van gekoppelde-resoneerderfilters deur die gebruik van modelgebaseerde parameteronttrekking

Van der Colff, A. P. E. 03 1900 (has links)
Thesis (MEng) -- Stellenbosch University, 2002. / ENGLISH ABSTRACT: The tuning of coupled-resonator filters is an essential part of its production. It is, however, a time consuming and expensive process. The use of model-based parameter extraction algorithms as a semi-automated tuning procedure is examined. This thesis describes the development of such a procedure. Different models for the filter are compared. The extraction algorithm is based on the least squares method. A more robust procedure is presented which makes the parameter extraction possible, without the availability of good starting values. The algorithm is evaluated using a fourth order single mode direct coupled cavity filter with a centre frequency of 10GHz. The algorithm produces good results and makes the tuning of this type of filter possible in an effective way. It also allows for the diagnosis of the filter, which is a great advantage over the more conventional direct tuning methods. / AFRIKAANSE OPSOMMING: Die instelling van gekoppelde-resoneerderfilters is ’n essensiele deel van die vervaardiging daarvan. Dit is egter ’n tydsame en duur proses. Die gebruik van modelgebaseerde parameteronttrekking as ’n semi-geoutomatiseerde instellingsproses is ondersoek. Hierdie tesis beskryf die ontwikkeling van so ’n prosedure. Verskillende modelle vir die filter is vergelyk. Die onttrekkingsalgoritme is gebaseer op die kleinste-kwadraatmetode. ’n Meer robuuste metode word voorgestel wat die parameteronttrekking moontlik maak, sonder dat daar goeie beginwaardes beskikbaar is. Die algoritme word geevalueer aan die hand van ’n vierde orde enkelmodus direkgekoppelderesoneerderfilter met ’n senterfrekwensie van 10GHz. Die algoritme lewer goeie resultate en maak die instelling van hierdie tipe filter moontlik op ’n effektiewe wyse. Die metode kan ook gebruik word vir die diagnose van die filter wat ’n groot voordeel is bo meer konvensionele direkte instellingsmetodes.

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