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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.
41

Design of Tunable/Reconfigurable and Compact Microwave Devices

Zhou, Mi 05 1900 (has links)
With the rapid development of the modern technology, radio frequency and microwave systems are playing more and more important roles. Since the time the first microwave device was invented, they have been leading not only the military but also our daily life to a new era. In order to make the devices have more practical applications, more and more strict requirements have been imposed. For example, good adaptability, reduced cost and shrank size are highly required. In this thesis, three devices are designed based on this requirement. At first, a symmetric four-port microwave varactor based 90-degree directional coupler with tunable coupling ratios and reconfigurable responses is presented. The proposed coupler is designed based on the modified structure of a crossover, where varactors are loaded. Then, a novel reconfigurable 3-dB directional coupler is presented. Varactors and inductors are loaded to the device to realize the reconfigurable performance. By adjusting the voltage applied to the varactors, the proposed coupler can be reconfigured from a branch-line coupler (90-degree coupler) to a rat-race coupler (180 degree coupler) and vice versa. At last, two types (Type-I and Type-II) of microwave baluns with generalized structures are presented. Different from the conventional transmission-line-based baluns where λ/2 transmission lines or λ/4 coupled lines are used, the proposed baluns are constructed by transmission lines with arbitrary electrical lengths.
42

Design of Multi Band Microwave Devices Using Coupled Line Transmission Lines

Katakam, Sri 05 1900 (has links)
Multi band technology helps in getting multiple operating frequencies using a single microwave device. This thesis presents the design of dual and tri band microwave devices using coupled transmission line structures. Chapter 2 presents the design of a novel dual band transmission line structure using coupled lines. In chapter 3, Design of a dual band branch line coupler and a dual band Wilkinson power divider are proposed using the novel dual band transmission line structure presented in the previous chapter. In chapter 4, Design of a tri band transmission line structure by extending the dual band structure is presented. The Conclusion and future work are presented in chapter 5.
43

Radial-Basis-Function Neural Network Optimization of Microwave Systems

Murphy, Ethan Kane 13 January 2003 (has links)
An original approach in microwave optimization, namely, a neural network procedure combined with the full-wave 3D electromagnetic simulator QuickWave-3D implemented a conformal FDTD method, is presented. The radial-basis-function network is trained by simulated frequency characteristics of S-parameters and geometric data of the corresponding system. High accuracy and computational efficiency of the procedure is illustrated for a waveguide bend, waveguide T-junction with a post, and a slotted waveguide as a radiating element.
44

Mixed boundary value problems in microstrip and geophysical probing applications

Chew, Weng Cho January 1980 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Weng Cho Chew. / Ph.D.
45

Analysis of Zincblende-Phase GaN, Cubic-Phase SiC, and GaAs MESFETs Including a Full-Band Monte Carlo Simulator

Weber, Michael Thomas 06 October 2005 (has links)
The objective of this research has been the study of device properties for emerging wide-bandgap cubic-phase semiconductors. Though the wide-bandgap semiconductors have great potential as high-power microwave devices, many gaps remain in the knowledge about their properties. The simulations in this work are designed to give insight into the performance of microwave high-power devices constructed from the materials in question. The simulation are performed using a Monte Carlo simulator which was designed from the ground up to include accurate, numerical band structures derived from an empirical pseudo-potential model. Improvements that have been made to the simulator include the generalized device structure simulation, the fully numerical final state selector, and the inclusion of the overlap integrals in the final-state selection. The first comparison that is made among the materials is direct-current breakdown. The DC voltage at which breakdown occurs is a good indication of how much power a transistor can provide. It is found that GaAs has the smallest DC breakdown, with 3C-SiC and ZB-GaN being over 3 times higher. This follows what is expected and is discussed in detail in the work. The second comparison made is the radio-frequency breakdown of the transistors. When devices are used in high-frequency applications it is possible to operate them beyond DC breakdown levels. This phenomenon is caused by the reaction time of the carriers in the device. It is important to understand this effect if these materials are used in a high-frequency application, since this effect can cause a change in the ability of a material to produce high-power devices. MESFETs made from these materials are compared and the results are discussed in detail.
46

Development of microwave and millimeter-wave pin grid array and ball grid array packages

Liang, Hongwei 12 1900 (has links)
No description available.
47

Design and development of compact and monolithic direct conversion receivers

Matinpour, Babak 05 1900 (has links)
No description available.
48

Field simulation and calibration in external electro-optic sampling /

Wu, Xiaohua. January 1996 (has links)
Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 196-205). Also available via World Wide Web.
49

Enhancement/depletion-mode HEMT technology for III-nitride mixed-signal and RF applications /

Wang, Ruonan. January 2008 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 86-101). Also available in electronic version.
50

Coplanar waveguide phase shifter on silicon at LMCS frequencies /

Picard, Stephan D., January 1900 (has links)
Thesis (M. Eng.)--Carleton University, 2001. / Includes bibliographical references (p. 171-174). Also available in electronic format on the Internet.

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