This thesis consists of two parts. Part one presents a design of class-AB power amplifier in 0.15£gm pHEMT process, and establishes a nonlinear model with memory effects for the power amplifier using Volterra series. To observe the memory effects, two-tone continuous wave signals have been applied to the model to predict the phase variation between IM3H and IM3L as a function of tone spacing. In the meanwhile, a time-domain measurement technique for the third-order intermodulation responses using a digital storage oscilloscope has been developed to verify the modeled predictions on IM3H and IM3L. Comparison between modeled and measured results shows good agreement. Part two of this thesis is to study the CMOS power-combining techniques. At first, the pros and cons between series and parallel combining transformers are discussed. Then, a design of class-E power amplifier using a pair of parallel combining transformers for power combining is presented. Both simulated and measured results show that the presented Class-E power amplifier has a high power-added efficiency.

The purpose of this work is to develop a maximum power tracking control strategy for variable speed wind turbine systems. Modern wind turbine control systems are slow, and they depend on the design parameters of the turbine and use wind and/or rotor speed measurements as control variable inputs. The dependence on the accuracy of the measurement devices makes the controller less reliable. The proposed control scheme is based on the stiff system concept and provides a fast response and a dynamic solution to the complicated aerodynamic system. This control scheme provides a response to the wind changes without the knowledge of wind speed and turbine parameters. The system consists of a permanent magnet synchronous machine (PMSM), a passive rectifier, a dc/dc boost converter, a current controlled voltage source inverter, and a microcontroller that commands the dc/dc converter to control the generator for maximum power extraction. The microcontroller will also be able to control the current output of the three-phase inverter. In this work, the aerodynamic characteristics of wind turbines and the power conversion system topology are explained. The maximum power tracking control algorithm with a variable step estimator is introduced and the modeling and simulation of the wind turbine generator system using the MATLAB/SIMULINK® software is presented and its results show, at least in principle, that the maximum power tracking algorithm developed is suitable for wind turbine generation systems.

Broadband over Power Line (BPL) technology has garnered significant attention lately due to recent advancements in solid state technologies and channel coding schemes. The successful application of BPL technology for in-home automation and networking has led to suggestions of applying BPL in other systems including ships. The application of BPL technology using the Shipboard Power System (SPS) as a potential communications network for ship automation systems has been proposed, to achieve recent U.S. Navy ship management concepts geared toward reducing ship manning while improving operational efficiency. This thesis presents an analytical model developed to examine the channel response characteristics and estimated throughput capacity of SPS cables. The work used a multiconductor transmission line theory based approach to model the channel response of SPS distribution lines and estimated the channel throughput capacity using a “water-filling” communication technique. This work found that BPL using the SPS holds a strong potential for use as a communications network for ship communication systems.

This dissertation aims to address two optimization problems involving power system reliabilty analysis, namely multi-area power system adequacy planning and transformer maintenance optimization. A new simulation method for power system reliability evaluation is proposed. The proposed method provides reliability indexes and distributions which can be used for risk assessment. Several solution methods for the planning problem are also proposed. The first method employs sensitivity analysis with Monte Carlo simulation. The procedure is simple yet effective and can be used as a guideline to quantify effectiveness of additional capacity. The second method applies scenario analysis with a state-space decomposition approach called global decomposition. The algorithm requires less memory usage and converges with fewer stages of decomposition. A system reliability equation is derived that leads to the development of the third method using dynamic programming. The main contribution of the third method is the approximation of reliability equation. The fourth method is the stochastic programming framework. This method offers modeling flexibility. The implementation of the solution techniques is presented and discussed. Finally, a probabilistic maintenance model of the transformer is proposed where mathematical equations relating maintenance practice and equipment lifetime and cost are derived. The closed-form expressions insightfully explain how the transformer parameters relate to reliability. This mathematical model facilitates an optimum, cost-effective maintenance scheme for the transformer.

Radio Frequency (RF) Power Amplifiers are responsible for a considerable amount of the power consumption in the entire transmitter-receiver (transceiver) of modern communication systems. The stringent linearity requirements of multi-standard transceivers to minimize cross-talking effects makes Linear Power Amplifiers, particularly class A, the preferred choice in broadband transceivers. This linearity requirement coupled with the fact that the Power Amplifier operates at low transmit power during most of its operation makes the efficiency of the entire transceiver poor. The limited transceiver efficiency leads to a reduction in the battery life of battery operated portable devices like mobile phones; hence drastically limiting talk time. To alleviate this issue, several research groups propose solutions to improve PA power efficiency. However, these solutions usually have a low efficiency at low power and are mostly limited to narrow bandwidth applications. In this thesis, the efficiency of a class A Power amplifier in wideband wireless standards like WiMax is improved by dynamically controlling the bias current and supply voltage of the PA. An efficient supply modulator based on a switching regulator architecture is proposed for controlling the supply voltage. The switching regulator is found to be slew-limited by the bulky inductor and capacitor used to regulate the supply voltage. The proposed solution alleviates the slew rate limitation by adding a bang-bang controlled current source. The proposed supply modulator has an average power efficiency of 81.6 percent and is suitable for wireless standards with bandwidths up to 20MHz compared to the relatively lower efficiencies and bandwidths of state of the art modulators. A class-A PA is shown to promise an average power efficiency of 21.3 percent when the bias current is controlled dynamically and the supply voltage is varied using the proposed supply modulator. This is a significant improvement over the poor average efficiency of 1.06 percent for a fixed bias conventional linear class A PA. The project has been simulated using the TSMC 0.18 micrometer technology.

This thesis consists of two parts. Part 1 introduces the characteristics of Class E power amplifier. Part 2 is focused on the implementation of Class E power amplifier for 2.4GHz Bluetooth applications. The design procedure follows the theory of class E power amplifier, and is implemented in MMICs and modules. For MMICs, the GaAs HBT foundry services are provided by the GCTC Ltd. and WIN Ltd.. Under single supply voltage of 3.3V and the output power of 20dBm, two designed MMICs have gain 23dB and 11dB, and power added efficiency (PAE) 57% and 72%, respectively. For Hybrid modules, RF transistors are provided by the Filtronic Ltd.. Under the same supply voltage of 3.3V, the measured output power, gain, and power added efficiency are 20 dBm, 25dB, and 75% respectively. Compared with the other types of power amplifiers on the market, Class E power amplifier has higher power added efficiency, and thus can increase the using time of communication system.

The purpose of this work is to develop a maximum power tracking control strategy for variable speed wind turbine systems. Modern wind turbine control systems are slow, and they depend on the design parameters of the turbine and use wind and/or rotor speed measurements as control variable inputs. The dependence on the accuracy of the measurement devices makes the controller less reliable. The proposed control scheme is based on the stiff system concept and provides a fast response and a dynamic solution to the complicated aerodynamic system. This control scheme provides a response to the wind changes without the knowledge of wind speed and turbine parameters. The system consists of a permanent magnet synchronous machine (PMSM), a passive rectifier, a dc/dc boost converter, a current controlled voltage source inverter, and a microcontroller that commands the dc/dc converter to control the generator for maximum power extraction. The microcontroller will also be able to control the current output of the three-phase inverter. In this work, the aerodynamic characteristics of wind turbines and the power conversion system topology are explained. The maximum power tracking control algorithm with a variable step estimator is introduced and the modeling and simulation of the wind turbine generator system using the MATLAB/SIMULINK® software is presented and its results show, at least in principle, that the maximum power tracking algorithm developed is suitable for wind turbine generation systems.

The 3D applications, until recently restricted to the desktops and workstations, are expanding into the mobile platforms, such as cellular phones and PDAs. Similar to the desktop, the consumers will expect high-quality 3D experience, and this is a big challenge. Handheld devices have slower processors that are less capable of computing large workloads, and the batteries have limited lifetimes, so for large and complex workload, we need an excellent power management policy for saving power. Besides, although mobile platforms have lower resolution than desktop, each pixel must still be rendered since the screen is closed to the observer¡¦s eye, or we will see some imperfections. For the reasons above, we make a point of performance optimization and power saving, and these rely on accuracy and fast workload estimation. We refer to some workload estimation methods which researchers have mentioned before, such as UW1, UW5, PID[8], Frame Structure[9], Signature Table[1], and hybrid power management policy[10].UW1 and UW5 both use the previous workload as the estimation workload. PID uses the feedback loop to correct the estimation workload. Frame Structure classifies frames into several structures, and sums the workload of each structure up as the estimation workload. Signature Table stores some 3D parameters in the table, and when a new frame comes in, the 3D parameters of this frame will compare with the table, if match, we use the workload in the table as the estimation workload. Our method is a hybrid policy of UW1 and UW5, and we will decide to use UW1 or UW5 when a new frame comes in. Finally we will compare the performance of each power management policy.

Abstract¡G This thesis studies the memory effect due to bias perturbation on digital predistortion technique, and employs multi-tone continuous wave signal and digital modulation signals with different bandwidth to discuss the performance of digital predistortion technique. Memory effect makes a great impact on the digital predistortion technique, and bias perturbation is one of the major causes. Lowering the bias perturbation can improve the effectiveness of digital predistortion technique. Another focus of this thesis is to design a Class E power amplifier in 0.18 £gm CMOS process. The power amplifier uses cascode structure to alleviate the breakdown voltage problem and employs power combining technique to achieve impedance transformation on chip for the purpose of increasing the output power and efficiency.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 274-276). Also available via the Internet.