Over the last few years‚ the number of subscribers of wireless services has increased at an explosive rate. This ever growing demand for wireless communications services is constantly increasing the need for better coverage‚ improved capacity and higher quality service. Smart antennas system is an effective technology for the performance improvement of wireless communications. Switching-beam smart antennas use a number of fixed beams at an antenna site. The system provides a beam that offers the best signal enhancement and interference reduction. Using the approach of dynamic switching-beam antenna system‚ an intelligent sector beam synthesis of adjustable sector width can be established. By doing so‚ traffic load balancing can be achieved, and therefore, system capacity is increased. In this thesis, a beam-pattern synthesis algorithm proposed by M.H. Er is applied to shape array patterns with an adjustable mainlobe width and average sidelobe level reduction. Using an established database of weighting for circular arrays, the proposed smart antennas can adjust suitable sectors for the high dense subscribers not uniformly distributed. Simulation results demonstrate the proposed technique can dramatically improve the performance of traditional switching-beam antennas.

In high-speed digital circuits, in order to utilize the space of printed circuit boards efficiently, the signal via is a heavily used interconnection structure to communicate different signal layers. However, the interconnection discontinuities will result in the degradation of the signal integrity and become a crucial issue for IC designers. To analyze the problems accurately and fast using the hybrid physical equivalent model which combining the transmission line model, slot model, via model, and decoupling capacitor model, etc. Based on the method, we can get a good result of simulation and compute faster than Ansoft HFSS. In addition, by the hybrid physical model method, we simulate and discuss several interesting issues such as resonance in power/ground planes, and the effect of the simultaneous switching noise, we also improve the bad effect of the printed circuit boards existing vias by some ways.

<p>This work has the approach for how an electric motor controller should be designed. In aircraft applications it is important that the system has a high power density, and that it is reliable. The target was to find out what is possible with technology of today, and with possibilities of tomorrow. The target is to be able to compare hydraulic systems with electrical ones.</p><p>The type of controllers that was studied was controllers for permanent magnetized synchronous machines (PMSM). The reason for that choice is that PMSM has a high efficiency. Different transistor technologies were evaluated. Discrete IGBT was found to be the best option. Of the evaluated transistors has IRG4PSH71U operating with a SiC freewheeling diode the best efficiency. The benefit with discrete components is that they are easy to cool, for example if they are distributed on an aluminium heatsink with forced air cooling.</p><p>To minimise losses and gain controllability on the motor should the inverter be controlled with some kind of vector control, such as DTC (Direct Torque Control).</p> / <p>I det här arbetet studerades hur en elmotorstyrning i ett flygplan bör konstrueras. I flygapplikationer är det viktigt att systemet är lätt i förhållande till effekten, och att det är tillförlitligt. Målet var att ta reda på vad man kan uppnå med dagens teknik, och även med kommande teknik. Syftet är att kunna jämföra hydrauliska system med elektriska.</p><p>Det som undersöktes var motorstyrningar till permanentmagnetiserade synkronmaskiner (PMSM), eftersom dessa motorer har en hög verkningsgrad. Olika transistortekniker utvärderades. Diskreta IGBT fanns vara det bästa valet i en sådan applikation. Av de transistorer som jämfördes har IRG4PSH71U tillsammans med en frihjulsdiod av SiC den bästa totala verkningsgraden. Det vill säga att summan av ledningsförluster och switchförluster är lägst för den kombinationen. Fördelen med diskreta transistorer är att de har en lägre termisk resistans och kan spridas på en kylfläns, vilket underlättar kylningen, t.ex. med en aluminiumkylfläns med forcerad luft kylning.</p><p>För att minimera förluster och öka styrbarheten på motorn bör växelriktaren styras med någon typ av vektor kontroll exempelvis DTC (Direct Torque Control).</p>

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: fair active queue management; RED; CSFQ; DRR; round trip time. Includes bibliographical references (p. 53-55).

Thesis (M.S. in Management)--Naval Postgraduate School, December 2009. / Thesis Advisor: Gates, William R. Second Reader: Summers, Donald E. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: lease, purchase, Alternative-fuel Vehicle (AFV), incremental costs, salvage values, General Services Administration (GSA), United States Marine Corps (USMC), light-duty vehicle. Includes bibliographical references (p. 61-63). Also available in print.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 131-133).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 132-139).

Thesis (M.S.)--University of Florida, 2002. / Title from title page of source document. Includes vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 98-103).

Wireless micro-sensors can enjoy popularity in biomedical drug-delivery treatments and tire-pressure monitoring systems because they offer in-situ, real-time, non-intrusive processing capabilities. However, miniaturized platforms severely limit the energy of onboard batteries and shorten the lifespan of electronic systems. Ambient energy is an attractive alternative because the energy from light, heat, radio-frequency (RF) radiation, and motion can potentially be used to continuously replenish an exhaustible reservoir. Of these sources, solar light produces the highest power density, except when supplied from indoor lighting, under which conditions the available power decreases drastically. Harnessing thermal energy is viable, but micro-scale dimensions severely limit temperature gradients, the fundamental mechanism from which thermo piles draw power. Mobile electronic devices today radiate plenty of RF energy, but still, the available power rapidly drops with distance. Harvesting kinetic energy may not compete with solar power, but in contrast to indoor lighting, thermal, and RF sources, moderate and consistent vibration power across a vast range of applications is typical. Although operating conditions ultimately determine which kinetic energy-harvesting method is optimal, piezoelectric transducers are relatively mature and produce comparatively more power than their counterparts such as electrostatic and electromagnetic kinetic energy transducers. The presented research objective is to develop, design, simulate, fabricate, prototype, test, and evaluate CMOS ICs that harvest ambient kinetic energy in periodic and non-periodic vibrations using a small piezoelectric transducer to continually replenish an energy-storage device like a capacitor or a rechargeable battery. Although vibrations in surrounding environment produce abundant energy over time, tiny transducers can harness only limited power from the energy sources, especially when mechanical stimulation is weak. To overcome this challenge, the presented piezoelectric harvesters eliminate the need for a rectifier which necessarily imposes threshold limits and additional losses in the system. More fundamentally, the presented harvesting circuits condition the transducer to convert more electrical energy for a given mechanical input by increasing the electromechanical damping force of the piezoelectric transducer. The overall aim is to acquire more power by widening the input range and improving the efficiency of the IC as well as the transducer. The presented technique in essence augments the energy density of micro-scale electronic systems by scavenging the ambient kinetic energy and extends their operational lifetime. This dissertation reports the findings acquired throughout the investigation. The first chapter introduces the applications and challenges of micro-scale energy harvesting and also reviews the fundamental mechanisms and recent developments of various energy-converting transducers that can harness ambient energy in light, heat, RF radiation, and vibrations. Chapter 2 examines various existing piezoelectric harvesting circuits, which mostly adopt bridge rectifiers as their core. Chapter 3 then introduces a bridge-free piezoelectric harvester circuit that employs a switched-inductor power stage to eliminate the need for a bridge rectifier and its drawbacks. More importantly, the harvester strengthens the electrical damping force of the piezoelectric device and increases the output power of the harvester. The chapter also presents the details of the integrated-circuit (IC) implementation and the experimental results of the prototyped harvester to corroborate and clarify the bridge-free harvester operation. One of the major discoveries from the first harvester prototype is the fact that the harvester circuit can condition the piezoelectric transducer to strengthen its electrical damping force and increase the output power of the harvester. As such, Chapter 4 discusses various energy-investment strategies that increase the electrical damping force of the transducer. The chapter presents, evaluates, and compares several switched-inductor harvester circuits against each other. Based on the investigation in Chapter 4, an energy-investing piezoelectric harvester was designed and experimentally evaluated to confirm the effectiveness of the investing scheme. Chapter 5 explains the details of the IC design and the measurement results of the prototyped energy-investing piezoelectric harvester. Finally, Chapter 6 concludes the dissertation by revisiting the challenges of miniaturized piezoelectric energy harvesters and by summarizing the fundamental contributions of the research. With the same importance as with the achievements of the investigation, the last chapter lists the technological limits that bound the performance of the proposed harvesters and briefly presents perspectives from the other side of the research boundary for future investigations of micro-scale piezoelectric energy harvesting.