Thesis (M. Ed.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 101-112).

Thesis (M.Ed.)--University of Hong Kong, 1997. / Includes bibliographical references (leaves 101-112). Also available in print.

M.Ing. (Electrical and Electronic Engineering) / Many applications need a high power (> 500W) at a relatively low voltage. The known technology of this class of converters is primitive and such converters are big as a result thereof. An investigation is made into the suitability of matrix transformer technology in the supply of large currents at low voltages. A layout for this topology which make optimal use of its characteristics is proposed . This includes modularity, possible application in distributed power supplies and equal current sharing. A system is designed and models are created to optimize the design. The models are extended to accommodate the effects of unavoidable parasitics which was observed in the practical system. A system consisting of sixteen modular units with a total output current capability of 320A at a voltage of between 0 and 5V is developed. The output capability and thus the number of modules needed is dependent on the application. Provision is thus made for a large power range. Power is transformed at a frequency of 100kHz to keep the physical dimensions of the system small.

In this dissertation, positive-real conformal transformations are used to develop synthesis procedures for the realization of driving-point immittance functions by exponentially- tapered distributed RC networks. These synthesis procedures include the realization by uniform distributed RC networks as a special case. New equivalent circuits are developed for the exponentially- tapered distributed RC network. These differ from the equivalent circuits for the uniform distributed RC network through the presence of positive and negative lumped elements and ideal transformers. It is found that the lumped elements must be eliminated from the equivalent circuits developed for exponentially tapered distributed RC networks before it is possible to apply a positive-real conformal transformation to change the synthesis problem into a lumped LC synthesis problem. Hence, through Richards Theorem, a cascade synthesis procedure for the realization of driving-point immittance functions is developed. Various cascade network realizations are presented. Additional distributed RC sections are used in these realizations to compensate for the lumped elements in the equivalent circuits. Before the synthesis procedure can be applied, it is necessary to approximate any specified driving-point immittance function by a function that is realizable by one of the network configurations presented. A digital computer with plotting facilities is deemed necessary for this purpose. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The purpose of this research is to develop, demonstrate, and characterize a novel architecture based on surface acoustic wave (SAW) devices capable of non-reciprocal propagation of forward and reverse signals. To begin, a novel topology is introduced based on asymmetrical delay lines and a current source representing a copy of the input signal. An analysis of this structure demonstrates it is capable of functioning as an isolator with the added capability of tuning the frequency response by controlling the phase relationships be- tween input signal and its copy. The structure is dependent on creating large phase shifts of 360◦ and 180◦ which is implemented in the acoustic domain. The current source functioning as a copy of the input signal is implemented by a parametric circuit. When a non-linear capacitor is pumped by a large signal at exactly twice the input signal frequency, an amplified copy of the input signal is reflected with a phase shift according to the pump signal phase due to the presence of negative resistance. This is precisely the behavior required for the topology to function. This type of parametric amplification is known as phase-coherent degenerate parametric amplifier. To investigate further, models are developed for the surface acoustic wave transducers, the non-linear capacitor, and the overall structure in Keysight’s Advanced Design Systems (ADS). Harmonic balance simulations in ADS verify the theory and demonstrate the same tunable behavior. These simulations are then used to design the SAW device and the peripheral circuitry required to match and isolate the pump signal from the input signal. The SAW device is fabricated on bulk LiN bO3 and bonded to a PCB board containing the pump circuitry. The first implementation is based on a bi-directional center transducer design and demonstrates overall functionality with limited bandwidth due to the single resonant parametric circuit design. A secondary device with a uni-directional SAW center transducer, which better matches the bandwidth of the input and output transducers, and a 2nd order resonant network result in improved performance demonstrating gain and isolation throughout the bandwidth of the SAW filter. Furthermore, the tunable aspect is also demonstrated by controlling the phase relationship between input and pump signals. This device, however, requires phase-coherence between signals and the relationship fP=2fS to be maintained. This is difficult to implement in practical systems and requires additional complicated circuitry. For this reason, a phase-incoherent version was also investigated. The addition of the uni-directional center transducer which couples the negative resistance to the acoustic waves, generates another form of asymmetry which also results in non-reciprocal propagation of forward and reverse signals. Due to its general applicability, the focus of the work is shifted to this prototype. The device is capable of functioning under different pump frequencies each with its advantages and disadvantages. For this reason, the performance both phase-coherent and incoherent modes of operation in terms of gain, isolation, noise, and linearity are characterized and understood under the lens of para- metric amplification. When compared to the state-of-the-art, the device exhibits superior performance in terms of isolation and insertion loss.

No description available.

Thesis (M.S.)--Ohio University, November, 1995. / Title from PDF t.p.

by Leung Tin Chi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 106-108). / Abstracts in English and Chinese. / Abstract / Acknowledgements / Table of Contents / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Balun Structures --- p.2 / Chapter 1.2 --- Balun Parameters --- p.4 / Chapter 1.3 --- LTCC Multi-layer Balun --- p.5 / Chapter 1.4 --- Original Contributions of The Thesis --- p.7 / Chapter Chapter 2 --- Background --- p.8 / Chapter 2.1 --- Lumped Elements Baluns --- p.8 / Chapter 2.1.1 --- λ/4 Transmission Line Equivalent Circuit Model --- p.10 / Chapter 2.1.2 --- 3λ/4 Transmission Line Equivalent Circuit Model --- p.14 / Chapter 2.1.3 --- Design Procedure of Lumped Element Balun --- p.18 / Chapter 2.2 --- Distributed Baluns --- p.29 / Chapter 2.2.1 --- Coupled Line --- p.29 / Chapter 2.2.2 --- Marchand Balun --- p.34 / Chapter 2.2.3 --- Stepped Impedance Balun --- p.38 / Chapter 2.2.4 --- New Structure Coupled-Line Balun --- p.53 / Chapter 2.3 --- Planar Balun --- p.63 / Chapter 2.4 --- Advantage and Disadvantage of Existed Balun Design --- p.69 / Chapter Chapter 3 --- Size Reduction Method of Coupled Lines --- p.71 / Chapter 3.1 --- New Proposed Method of Coupled Line Size Reduction --- p.71 / Chapter 3.2 --- Simulation Result of Capacitor Loaded Coupled Line --- p.77 / Chapter Chapter 4 --- Capacitor Loaded Coupled Line Balun --- p.82 / Chapter 4.1 --- Simulation Result of Capacitor Loaded Coupled-Line Balun --- p.82 / Chapter Chapter 5 --- Design of New Coupled Line Balun Using Capacitor Loaded Coupled Lines --- p.88 / Chapter 5.1 --- Design Specifications of Reduced Coupled-Line Balun --- p.89 / Chapter 5.2 --- Design of Capacitors --- p.90 / Chapter 5.3 --- Layout and Simulation Result of 2.4GHZ LTCC Capacitor Loaded Coupled-Line Balun --- p.96 / Chapter Chapter 6 --- Conclusion and Future Work --- p.104 / References --- p.106 / Author's Publication --- p.109 / Appendix A Marchand Balun --- p.110 / Appendix B Reconstruction of S-Matrix for a 3-Port Measurement at Only Two-Ports --- p.117 / Appendix C Renormalization of Balun S-Matrix with Load Termination Z1 from S-Matrix with Load Termination Z0 --- p.120 / Appendix D Sensitivity analysis for capacitor loaded coupled line balun --- p.122

No description available.

No description available.