Low cost bandpass filters (less than $100) at microwave frequencies cannot be purchased commercially. However, such filters are essential in the design of RF circuits in communications and radar equipment. Reliable microstrip band pass filters which provide an accurate filter response at microwave frequencies can be easily fabricated with low cost. Equations concerning the design of coupled microstrips and microstrip filters are published in the literature and were implemented in a design procedure for maximally flat microstrip band pass filters. The published equations were theoretical and had not been extensively compared with experimental data. Thus, this work established an enhanced microstrip filter design procedure based on experimental data, for a wide range of frequencies and dielectric substrates. The result of this work is an enhanced design procedure for microstrip band pass filters. The new procedure includes a correction factor for the length of the filter resonators which which controls the center frequency of the filter. This correction factor has been found from the measured responses of over 60 filters, which were designed with two different circuit board materials, three different substrate thicknesses, and frequencies ranging between 0.9 and 6 GHz. The experimentally determined length correction factor decreases the error in center frequency from ±5.9% down to ±L7% of the desired design frequency for a wide range of filter designs. The improved procedure has been implemented in a personal computer (PC) program which calculates all dimensions necessary to fabricate microstrip band pass filters in the low microwave frequency range. The maximally flat response obtained is accurate and requires very little tuning. Low cost microstrip band pass filters can now be designed and fabricated easily and with greater accuracy at microwave frequencies. This thesis describes the development of the enhanced design procedure and the results of the filters designed with the new procedure. / Master of Science

Moving-average matched filters (MAMF's) are a class of digital filters used to detect the presence of a known signal in noise. Designing matched filters requires knowledge of the structure of the signal and the noise. If the spectral density of the noise is not known or is changing with time its spectral characteristics must be estimated. Since spectral estimators derive their estimates from a random process realization, the estimates themselves are probabilistic in nature. The performance of MAMF's based on these estimates must, in turn, be distributed in a probabilistic sense. This thesis investigates the performance of MAMF's designed on the basis of several different spectral estimators. Theoretical aspects of MAMF's and spectral estimators are reviewed and developed. A simulation system is used to exercise the spectral estimators and MAMF's and to provide comparative performance data. A graphical representation, using contour plots, is developed and can be used to predict the performance of a given MAMF/signal/spectral estimator combination. Finally, several methods of generating MAMF's whose output performance is relatively insensitive (or robust) to the probabilistic variations caused by the spectral estimators are developed and evaluated. The latter incorporates knowledge of the empirical distribution of the particular spectral estimator used, as well as the freedom of manipulating the signal. / M.S.

Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics & Engineering, 2008. / "March, 2009". Bibliography: p. 145-158.

Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Multi-mode coupled cavity filters have been the mainstay of commercial satellite communications systems since their introduction in 1970. Multi-mode filters use more than one resonant mode in a single cavity resonator, thereby reducing the size and weight of the filter. This is especially advantageous for satellite applications where the size and weight of the communications payload must be minimised. The use of more modes also increases the complexity of the filter design. Iris design plays an integral part in the design of multi-mode coupled cavity filters. Currently, irises are mostly designed using either the small aperture theory derived by Bethe, or a standard numerical technique. A recent study comparing these two techniques shows that approximations made in standard correction factors applied to small aperture theory, can lead to unacceptable errors. While numerical techniques are clearly required for the accurate design of complex irises, the standard numerical technique is only suited to the design of relatively simple iris structures. This dissertation presents three new CAD procedures for the design of irises in multi-mode coupled cavity devices. The new procedures are verified by numerical examples and measurements. Two new multi-mode coupled cavity devices were designed and tested using the CAD procedures developed in this work. The first is a new diplexer structure that realises two fourth order Chebyschev filter channels in three quadruple-mode cavities. Through correct placement and accurate design of irises, channel isolation was increased beyond that of existing multi-mode diplexer structures. The second application is the development of a new coupling structure for the replacement of coupling and tuning screws. A third order triple-mode cavity filter, including this new fixed coupling element, was designed using the CAD procedures developed in this dissertation. / AFRIKAANSE OPSOMMING: Multi-modale gekoppelde resoneerder filters word reeds vanaf die eerste verskyning van kommersiele sateliet-kommunikasiestelsels in 1970 gebruik. Vir hierdie toepassing is die fisiese grootte en massa van die filters in die kommunikasiestelsels van groot belang. Multimodale filters gebruik meer as een resonante modus in ‘n golfgeleier resoneerder om die fisiese grootte en massa van die filter te verminder. Hoe meer resonante modusse in een golfgeleier resoneerder, hoe kleiner en ligter die filter. Die gebruik van meer modusse kompliseer egter die ontwerp van die filter. ‘n Baie belangrike aspek van multi-modale filterontwerp is die ontwerp van die irisse wat die golfgeleier resoneerder skei. Die irisse word tans ontwerp, of deur middel van Bethe se klein iris teorie, of met die gebruik van ‘n standaard numeriese metode. ‘n Onlangse studie toon aan dat sekere standaard toevoegings tot Bethe se teorie, benaderings bevat wat tot foutiewe iris ontwerp kan lei. Numeriese metodes is dus noodsaaklik vir akkurate iris ontwerp. Hierdie studie wys egter dat die bestaande numeriese tegnieke beperk is tot die ontwerp van relatief eenvoudige irisse. Hierdie proefskrif bied drie nuwe rekenaargesteunde ontwerpsprosedures vir die doeltreffende ontwerp van verskillende klasse irisse in multi-modale golfgeleier resoneerder filters. Die nuwe metodes word getoets aan die hand van numeriese voorbeelde, en/of gemete resultate. Twee nuwe komplekse multi-modale golfgeleier resoneerder filter toepassings is ontwerp deur gebruik te maak van die nuwe ontwerpsprosedures. Die eerste is ‘n nuwe diplekser struktuur met twee vierde-orde Chebyschev filterkanale in drie golfgeleier resoneerders wat elk vier resonante modusse ondersteun. Deur korrekte en akkurate plasing van die irisse word ‘n groot verbetering in kanaalisolasie bo ‘n bestaande multi-modale diplekser verkry. Die tweede toepassing is die ontwikkeling van ‘n nuwe koppelstruktuur vir die vervanging van die gebruiklike koppel- en aanpassingskroewe. ‘n Derde-orde trippel-modus filter, gebaseer op hierdie nuwe struktuur, is ook ontwerp deur van die nuwe ontwerpsalgoritmes gebruik te maak.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

by Tai Leong Charn. / Bibliography: leaves R-i-iii / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

Chok-ki Chan. / Bibliography: leaves 117-122 / Thesis (Ph.D.) - Chinese University of Hong Kong, 1984

Law, Carlos. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 119-122). / Abstracts in English and Chinese. / Abstract --- p.i / 論文摘要 --- p.iii / Acknowledgement --- p.v / Table of Content --- p.vi / List of Figures --- p.ix / List of Tables --- p.xv / List of Abbreviations --- p.xvi / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Emergence of Multi-band Microwave Circuits --- p.1 / Chapter 1.2 --- Original Contribution --- p.2 / Chapter 1.3 --- Overview of the Thesis Organization --- p.3 / Chapter 1.4 --- "Research Approach, Assumptions and Limitations" --- p.5 / Chapter Chapter 2： --- Fundamentals in Filter and Power Divider Design --- p.7 / Chapter 2.1 --- Filter --- p.7 / Chapter 2.1.1 --- Introduction to Filters --- p.7 / Chapter 2.1.2 --- Transfer Function --- p.8 / Chapter 2.1.3 --- Low-pass Prototype and Elements --- p.11 / Chapter 2.1.4 --- Admittance Inverters --- p.13 / Chapter 2.2 --- Power Divider --- p.20 / Chapter 2.2.1 --- Introduction to Power Dividers --- p.20 / Chapter 2.2.2 --- Wilkinson Power Divider --- p.21 / Chapter 2.2.3 --- Multi-section Power Divider --- p.25 / Chapter 2.2.4 --- Power Divider with Unequal Power Division --- p.27 / Chapter Chapter 3： --- Conventional Multi-band Designs --- p.29 / Chapter 3.1 --- Micro-strip Multi-band Filters --- p.29 / Chapter 3.1.1 --- Parallel Connection of Two Single-band Filters --- p.29 / Chapter 3.1.2 --- "Wide-band, Band-pass Filter and a Band-stop Filter in Cascade" --- p.32 / Chapter 3.1.3 --- Parallel-coupled SIR-based Dual-band Filter --- p.33 / Chapter 3.1.4 --- Vertical-stacked SIR-based Dual-band Filter --- p.34 / Chapter 3.1.5 --- Cross-coupled Hairpin SIR Dual-band Filter --- p.37 / Chapter 3.1.6 --- Folded Open-loop Ring Resonator-based Multi-band Filters --- p.38 / Chapter 3.1.7 --- Stubbed SIR-based Single-band Filter --- p.40 / Chapter 3.1.8 --- Open and Short-circuited Stub-based Dual-band Filter --- p.41 / Chapter 3.1.9 --- Open Stub-based Dual-band Filter --- p.42 / Chapter 3.2 --- Spurious Suppression Techniques for Filters --- p.43 / Chapter 3.2.1 --- Insertion of Band-reject Filters --- p.43 / Chapter 3.2.2 --- Equalization of Eigen-mode Phase Velocities --- p.43 / Chapter 3.2.3 --- Insertion of Open Stubs --- p.45 / Chapter 3.2.4 --- Coupled SIR-based Structures --- p.47 / Chapter 3.2.5 --- Parallel Coupled Line --- p.49 / Chapter 3.2.6 --- Others --- p.50 / Chapter 3.3 --- Dual-band Power Dividers --- p.51 / Chapter 3.3.1 --- Two-section Transmission Line Topology --- p.51 / Chapter 3.3.2 --- Lumped Element-based Topology --- p.53 / Chapter 3.3.3 --- Shunt Stub Topology --- p.56 / Chapter Chapter 4: --- New Dual-band Filter with Wide Upper Stop-band … --- p.59 / Chapter 4.1 --- Proposed Topology --- p.60 / Chapter 4.2 --- Design and Analysis --- p.61 / Chapter 4.3 --- Design Example --- p.73 / Chapter 4.4 --- Summary --- p.79 / Chapter Chapter 5: --- New Tri-band Filter Design --- p.80 / Chapter 5.1 --- Proposed Topology --- p.80 / Chapter 5.2 --- Design and Analysis --- p.82 / Chapter 5.3 --- Design Example --- p.86 / Chapter 5.4 --- Summary --- p.91 / Chapter Chapter 6: --- New Dual-band Power Divider Design I --- p.92 / Chapter 6.1 --- Proposed Topology --- p.92 / Chapter 6.2 --- Design and Analysis --- p.94 / Chapter 6.3 --- Design Example --- p.98 / Chapter 6.4 --- Summary --- p.107 / Chapter Chapter 7: --- New Dual-band Power Divider Design II --- p.108 / Chapter 7.1 --- Proposed Topology --- p.108 / Chapter 7.2 --- Design and Analysis --- p.109 / Chapter 7.3 --- Design Example --- p.112 / Chapter 7.4 --- Summary --- p.115 / Chapter Chapter 8: --- Conclusion --- p.116 / Recommendation for Future Work --- p.118 / References --- p.119 / Author's Publications --- p.123 / Appendix 1: ABCD Parameters --- p.124 / Appendix 2: Program for Tri-band Filter --- p.125 / Appendix 3: Comparison of Dual-band Power Dividers --- p.129 / Appendix 4: Sensitivity of Power Divider to Resistor Variation --- p.146

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 76-77).

Pulse Width Modulation (PWM) has been used extensively for motor control, DC-AC converters, DC-DC converters and in audio applications. The conventional method of generating a pulse width modulated signal involves generating an accurate sawtooth or triangle wave using analog circuits. In CMOS, being analog circuit intensive puts extra constraints on the fabrication process used for manufacture, thus requiring a higher cost than digital CMOS. Delta-Sigma Modulation on the other hand is analog intensive, but requires only quality capacitor matching, which can be obtained with current digital CMOS processes. This thesis describes a method to generate a digital PWM with pulse dithering using a Delta-Sigma modulator. The Delta-Sigma modulator provides accuracy and allows the circuit to be implemented in a digital CMOS process, while the pulse dithering in the PWM spreads out harmonic noise generated from the PWM fundamental frequency. / Graduation date: 1998