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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

The Luminescence Properties of ZnO Thin Films Prepared by Room Temperature Sputtering Process

Hu, Chun-Chieh 25 July 2005 (has links)
In this study, the reactive rf magnetron sputtering was used to deposit zinc oxide (ZnO) thin films on SiO2/Si substrate at room temperature. The thermal treatment procedure was carried out to improve the luminescence characteristics of ZnO thin films. The physical characteristics of ZnO thin films with different post annealing process were obtained by the analyses of XRD and SEM. The electron spectroscopy for chemical analysis (ESCA) was used to analyze the chemical states of ZnO thin films. In optical properties, the photoluminescence spectrometer was used to measure the photoluminescence characteristics (PL). According to the results of experiments, the chemical states of ZnO thin films were changed after different post annealing. The photoluminescence characteristics were obtained at different wavelength, and the results indicated that they were affected by the chemical states of ZnO thin films. With 900¢J annealing, the strongest green emission and UV emission intensity can be obtained under the air ambient and the oxygen ambient, respectively. The reason was due to the variation of the proportion of oxygen vacancies and O-Zn bond within the ZnO thin films.
242

A Study of Flexural Plate Wave Device with High C-axis Orientation ZnO Piezoelectric Film and Interdigital Transducer

Chang, Yi-Wen 13 July 2006 (has links)
By integrating Nanotechnology and MEMS technology, this thesis aims to research a flexural-plate wave (FPW) sensor for testing Immunoglobulin E (IgE) concentration in blood serum, a significant index for the diagnosis of allergies. The traditional methods of blood assay are time-consuming and costly, and its average accuracy of only 60-70 percent. After compare the major four kinds of acoustic sensor, the FPW sensor demonstrates a high accuracy, high sensitivity, low operation frequency, low diagnosis time and low cost. This thesis utilizes a reactive RF sputter system to deposite the piezoelectric ZnO thin film. To obtain the high C-axis orientation (002) characteristic of ZnO membrane, many parameters such as substrate temperature, Ar/O2 ratio and RF power have been adjusted and optimized during the sputtering process. The effects of varied parameters will be investigated and analysis by using SEM or XRD facilities. In this study, we combined the high figure-of-merits ZnO deposition techniques and single-side anisotropic silicon etch process to implement the process integration of FPW device. Finally, this research has demonstrated a 50-60MHz center frequency can be extracted from such silicon-based FPW microsensor.
243

The Design and Implementation of RFICs for DVB-H Tuner Applications

Li, Shu-Lin 15 July 2006 (has links)
This research aims to design a dual-conversion tuner RFIC for DVB-H applications with EDA tools. In order to have good understanding of the EDA tools used, both time-domain and frequency-domain simulation techniques are studied and discussed in this thesis. The designed tuner RFIC is implemented by a TSMC 0.35£gm SiGe BiCMOS process. The parasitic effects from PCB interconnects are also considered in this work. We use 3-D quasi-static EM simulation tool to extract the parasitic elements for PCB interconnects, and co-simulate these parasitic elements with RFICs using circuit simulation tool. The implemented tuner RFIC integrates most key components into a single chip, including the variable-gain low noise amplifier, up-converting mixer, intermediate-frequency amplifier, and down-converting mixer. Under QPSK modulation test, the designed tuner RFIC shows a wide dynamic range with good protection ratio. In addition, it has a low power consumption and thus is suitable for use in portable digital TV equipments.
244

The study of AlN thin film grown on bottom electrode under room temperature condition

Huang, Ching-Ju 15 May 2000 (has links)
In this study, highly C-axis oriented AlN thin films stacked upon Al bottom electrode on Si and Glass substrate are deposited with Reactive RF magnetron sputtering Technique. Three different sputtering systems were utilized to evaluate the optimized growth parameters. Room temperature growth was applied to the all system. During thin film growing , the substrate bias condition, sputtering work pressure, sputtering power and the N2 concentration are those key parameters to be adjusted in order to gain smooth surface morphology and highly C-axis prefer orientation AlN thin films. The crystallography of the deposited films was analyzed by x-ray diffraction (XRD). Film surface morphology was characterized by scanning electron microscopy (SEM). Meanwhile, transmission electron microscopy (TEM) was adopted to observe the microstructure and determine the grain size of the film. The results of the XRD patterns showed that in a 17cm long sputtering working distance condition, the AlN (002) can be obtained and the peak intensity can be increased when the sputtering power was fixed meanwhile reduced the working pressure and applied the negative bias on the substrate. The surface morphology can be improved with long working sputtering distance. The micrography of the TEM reveals that there is a transition region between Al metal and AlN film. Fine column structures can be observed in the initial growth stage. The size of the grain increased as the film became thicker. Strong AlN (002) ring pattern was obtained from the region of the top of the film. It indicates that the AlN (002) will not appear till the thickness of the film reach the critical thickness.
245

Development of IEEE 802.11b RF Transceiver Modules

Han, Fu-Yi 10 July 2003 (has links)
This thesis consisted of three parts. Part 1 introduced the design procedure of an RF transceiver modules for IEEE 802.11b WLAN system. It contained the selection of RF architectures, frequency planning, and the receiver link budget analysis flow. Part 2 focused on the implementation of each stage in the whole RF link. The design considerations of choosing passive elements and the parasitic effect of the evaluation board are discussed. Part 3 integrated the whole RF transceiver module and estimated the performance of this module through the link budget analysis method. Furthermore, a complete specification measurement was accomplished by using the standard test signals. The test results confirmed with the budget results, and also pass the specification of IEEE 802.11b WLAN system.
246

Development of the Four Cellular-Band RF Loadboard for Mass Production on Automatic Test Equipment

Tsai, Wen-Fu 18 July 2008 (has links)
This research aims at the development of a RF mass production load board for 4 bands cellular phone (850 MHz GSM-USA, 900 MHz GSM, 1.8 GHz DCS and 1.9 GHz PCS). To construct a strong theoretical foundation, the characteristics of key components such as relays, balun, cables, vias, micro strip line on the load board and the RF rules for PCB layout are extensively studied. An experimental load board is also specially designed to study the characteristics of RF printed circuit board. In this experimental load board, different materials (FR4 and Rogers) and transmission lines (microstrip lines and differential lines) are specially made and measured. After studying this experimental load board, we co-work with the RF load board supplier KeyStone to do the simulation as the preparation of production load board. In this simulation, the actual layout (Gerber file) of critical path together with the socket is checked for the resonance frequency. The production load board is manufactured in FR4 and debugged in the off-line debugging station before a correlation process in the ATE (automatic test equipment). Fine tune of 4 bands matching circuit is done by changing the value and/or the position of component on the matching circuit with VNA. After the fine tune, 70 good devices were tested twice on the same u-Flex tester with the developed load board and the one sent from test center in Europe (reference loadboard). The test results are processed by statistics tool ¡§Data Power¡¨ to calculate the mean value, variance, Cpk (biased process capability), R&R (Repeatability and Reproducibility), etc. The statistics results show the performance of the developed RF load board and the one from the test center in Europe is compatible and can be released for mass production. From this research, design flow of RF loadboard, highly relies on simulation to guarantee the performance of RF loadboard instead of basing on experience and/or trial and error, has been built up
247

Design and Simulation of High Quality-factor Microinductors for Wireless Communication System Applications

Hung, Kun-ting 11 August 2008 (has links)
This paper aims to design a high-quality-factor suspending micro-inductor and to establish its equivalent circuit model for performance optimization. Two commercial software (Ansoft HFSS and Agilent ADS) are adopts to analysis the influences of quality factor on the geometric parameters and substrate materials. The designed micro-inductors are constructed by one bottom GSG electrode, two supporting copper vias and a spiral suspending copper conducting layer. As the simulated results of this research, the quality factor of the suspending micro-inductor is increased with the height of air gap, the thickness and width of suspending copper conducting layer and decrease with the number of turns, line space and outer diameter of suspending copper conducting layer. The influences of different shapes of the spiral suspending copper conducting layers on the quality factor of micro-inductors were also investigated. The simulation results well match to the theoretical prediction. Finally, this thesis has successfully derived two experiential formulas based on the analysis results to estimate quickly the inductance of the suspending micro-inductors with circular and square shape. Compared with the simulation results and realistic measurement results, these experiential formulas demonstrate 94-95% and 90% accuracies respectively.
248

Research on Digitally Predistorted Power Amplifier and Injection-Pulled Oscillator for Wireless Communication System

Li, Chien-Jung 26 July 2009 (has links)
In a wireless communication system, the RF signal integrity is often deteriorated by power amplifier (PA) nonlinearity and local oscillator (LO) pulling. This dissertation attempts to study power amplifier and local oscillator with the deliberate input distortion or interference for understanding, and hence improving, the resultant RF signal integrity issues. Furthermore, the scope of this study is extended to explore novel wireless applications. Based on the above thoughts, this dissertation includes three topics. The first topic is devoted to a baseband digital predistortion technique for enhancing the power amplifier linearity in a wireless RF transmitter. A digital predistorter has been designed to compensate the amplitude and phase distortion due to the nature of PAs, and the predistortion can enhance the linearity of linear PAs as well as switching-mode PAs. The second topic proceeds with a rigorous analysis of a local oscillator subject to injection signal. A phase-locked loop (PLL) under injection is analyzed in frequency domain to account for the inherent band-pass filtering on an injection signal. Such analysis can further predict the effect of co-frequency or co-channel interference on the PLL phase noise. A discrete-time analysis is also provided to predict output spectra of the LO pulled by a sinusoidal and modulated injection signal. The final topic presents a novel RF sensing circuit for a cognitive radio to sense spectral environment using injection locking and frequency demodulation techniques. The proposed RF sensing circuit can fast and reliably detect frequency and power for analog and digital modulation signals. In addition, the sensing principle and circuit architecture are delivered on theoretical basis developed in this dissertation. A discrete time approach is also investigated to compute the sensed output signal.
249

Simulation and Optimization of SiC Field Effect Transistors

Bertilsson, Kent January 2004 (has links)
<p>Silicon Carbide (SiC) is a wide band-gap semiconductor material with excel-lent material properties for high frequency, high power and high temperature elec-tronics. In this work different SiC field-effect transistors have been studied using theoretical methods, with the focus on both the devices and the methods used. The rapid miniaturization of commercial devices demands better physical models than the drift-diffusion and hydrodynamic models most commonly used at present.</p><p>The Monte Carlo method is the most accurate physical methods available and has been used in this work to study the performance in short-channel SiC field-effect devices. The drawback of the Monte-Carlo method is the computational power required and it is thus not well suited for device design where the layout requires to be optimized for best device performance. One approach to reduce the simulation time in the Monte Carlo method is to use a time-domain drift-diffusion model in contact and bulk regions of the device. In this work, a time-domain drift-diffusion model is implemented and verified against commercial tools and would be suitable for inclusion in the Monte-Carlo device simulator framework.</p><p>Device optimization is traditionally performed by hand, changing device pa-rameters until sufficient performance is achieved. This is very time consuming work without any guarantee of achieving an optimal layout. In this work a tool is developed, which automatically changes device layout until optimal device per-formance is achieved. Device optimization requires hundreds of device simulations and thus it is essential that computationally efficient methods are used. One impor-tant physical process for RF power devices is self heating. Self heating can be fairly accurately modeled in two dimensions but this will greatly reduce the computa-tional speed. For realistic influence self heating must be studied in three dimensions and a method is developed using a combination of 2D electrical and 3D thermal simulations. The accuracy is much improved by using the proposed method in comparison to a 2D coupled electro/thermal simulation and at the same time offers greater efficiency. Linearity is another very important issue for RF power devices for telecommunication applications. A method to predict the linearity is imple-mented using nonlinear circuit simulation of the active device and neighboring passive elements.</p>
250

Development and Usage of IF Recorders in Range Systems

Salisbury, Jack, Cornelius, Harold E., Pennington, Gregory A. 10 1900 (has links)
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / Accurate reproduction of RF transmissions for test and development has been out of reach for some time. The testing of RF equipment, multipath generation and downstream TM processing systems has been done in the past with varying levels of accuracy. In the past the techniques of checking TM equipment worked, but lacked realism that real TM transmissions provide. This paper describes the development of an IF recorder for range TM. We discuss the usage of a recorder with multiple channels, time correlation, channel skew capability, IF over IP capabilities and file management will allow repeatable, realistic testing of TM systems.

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