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Title: Design and analysis of microwave communication system components : resonator, oscillator and frequency doubler
Other Titles: Wei bo tong xun xi tong yuan jian zhi she ji yu fen xi : xie zhen dan yuan, zhen dang qi he bei pin qi
微波通訊系統元件之設計與分析 : 諧振單元, 振蕩器和倍頻器
Authors: Lau, Yeung Fan (劉揚帆)
Department: Dept. of Electronic Engineering
Degree: Doctor of Philosophy
Issue Date: 2005
Publisher: City University of Hong Kong
Subjects: Microwave communication systems -- Design and construction
Notes: CityU Call Number: TK7876.L36 2005
Includes bibliographical references.
Thesis (Ph.D.)--City University of Hong Kong, 2005
x, 109 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: In this thesis, three novel microwave components for communication system have been developed. Design and analysis are conducted along the three areas including: compact microstrip resonant cell (CMRC) (Chapter 2), oscillator (Chapter 3) and frequency doubler (Chapters 4~6). Chapter 1 shows some research background and highlights. The thesis also includes other research work done during the course of the Ph.D. study, which is attached in Appendices. 1. CMRC design and analysis (Chapter 2) Compact microstrip resonant cell (CMRC), a quasi-lumped microstrip structure with specific pattern etched on the signal line, exhibits slow-wave and band-stop characteristics. This thesis presents some study results on the structure and its applications in the design of antenna switch (Chapter 2) and frequency doubler (Chapter 4). When applying the CMRC, it is necessary to develop a design methodology such that the location of the stop-band can be controlled for a given size constraint at various application scenarios. The study shows that the dimension and the etched pattern are critical to its performance. 2. Oscillator design and analysis (Chapter 3) Generally, transistor oscillator’s output second harmonic should be prevented leakage to subsequent circuits and degrade overall system performance. But there is little control of the harmonic level of most oscillators unless an output filter is used. Chapter 3 shows that an antiparallel transistor pair configuration can be applied in oscillator design without filter for compactness. Experimental results verify the methodology with a more than 20 dB improvement in second harmonic rejection, as compared to a conventional oscillator. 3. Frequency doubler design and analysis (Chapters 4~6) Frequency doubler plays an important role in realizing stable and cost-effective local source in the wireless communications systems. For a general-purpose frequency doubler, the requirements are high conversion gain, good rejection of fundamental and other unwanted harmonics. To meet these requirements, three novel design approaches have been developed analytically and verified experimentally. The first design (Chapter 4) employs the CMRC to provide reactive reflections for both the second and third harmonics. By choosing the reflection phases at the input port of the active device, the second and third harmonics are constructively and destructively interfered, respectively. In addition, the CMRC has a good pass-band for the fundamental frequency and, hence, it maintains a good input VSWR. Consequently, the proposed method has a gain enhancement for the second harmonic over the conventional stub approach. The second proposed design (Chapter 5) is an active harmonic termination technique. It entails a parallel connection of a transistor pair, with one of them functions primarily as an active harmonic termination for the other. By taking advantage of the two active device input and output impedances, and utilizing the transmission lines connecting them, the frequency harmonic components concerned at the input and output networks are suitably terminated. The new design can reduce circuit area, achieve higher conversion gain, better spectrum purity and wider operating bandwidth, as compared to the conventional single-ended or balanced configurations. The third design (Chapter 6) adopts the ideas of negative-resistance in active filter and reflection-type in amplifier designs. Although reflection-type amplifier has the high-gain feature, the necessary presence of the bulky circulator for input/output fundamental frequency isolation keeps the design remaining mostly in conceptual level. In the case of frequency doubler, we can still maintain the high-gain feature, while desirably replace the circulator with filters or ring resonator, due to the circuit’s inherent input/output frequency separation. If a wider negative-resistance region could be obtained, the new circuit would have a broader operating bandwidth. Also, the structure resembles a varactor diode doubler configuration, leading to a low noise characteristic.
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