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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.
251

Initial iNET RF Networking Testing

Timme, M. Wayne, Newton, Todd A., Moodie, Myron L., Abbott, Ben A., Grace, Thomas B. 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 / One of the core philosophies of the integrated Network Enhanced Telemetry (iNET) project is to leverage standard networking technologies whenever possible to both reduce development cost and to allow standard networking applications to function properly. This also provides the best long-term scalability to new unforeseen applications much as the Internet has grown through its open standards. Unfortunately, the Radio Frequency (RF) channel characteristics do not fully lend themselves to the typical physical layer approaches utilized by Internet Protocol (IP) technologies. The iNET project is developing the Telemetry Network System (TmNS) RF Network to provide a flexible two-way IP telemetry capability. The Developmental Flight Test (DFT) phase is currently under way to perform initial flight testing of the RF Network. This paper provides an overview of the planned RF network testing and the expected results. Current results from flight testing will be presented at the conference.
252

Ηλεκτρομαγνητική μοντελοποίηση στις VHF και UHF περιοχές συχνοτήτων

Ψαχούλιας, Γεώργιος 18 August 2008 (has links)
Στόχος της παρούσας διπλωματικής εργασίας είναι η ηλεκτρομαγνητική μοντελοποίηση υπό βρoχόπτωση στις VHF και UHF περιοχές συχνοτήτων. Προκειμένου να εξαχθούν συμπεράσματα για την ποιότητα των παρεχόμενων υπηρεσιών (κυτταρική και δορυφορική τηλεφωνία, μετάδοση τηλεοπτικών σημάτων) προσδιορίζονται η ισχύς λήψης και μία σειρά από παραμέτρους. / The aim of this master thesis is the RF modeling during rainfall for the VHF and UHF ranges. In order to infer conclusions for the quality of the supplied services (cellular and satellite telephony, transmission of television signals) the received power and a series of parameters are defined.
253

Compact modeling of the rf and noise behavior of multiple-gate mosfets

Nae, Bogdan Mihai 29 April 2011 (has links)
La reducción de la tecnología MOSFET planar ha sido la opción tecnológica dominante en las últimas décadas. Sin embargo, hemos llegado a un punto en el que los materiales y problemas en los dispositivos surgen, abriendo la puerta para estructuras alternativas de los dispositivos. Entre estas estructuras se encuentran los dispositivos DG, SGT y Triple-Gate. Estas tres estructuras están estudiadas en esta tesis, en el contexto de rducir las dimensiones de los dispositivos a tamaños tales que los mecanismos cuánticos y efectos de calan coro deben tenerse n cuenta. Estos efectos vienen con una seria de desafíos desde el pun to de vista de modelación, unos de los más grandes siendo el tiempo y los recursos comprometidos para ejecutar las simulaciones. para resolver este problema, esta tesis propone modelos comlets analíticos y compactos para cada una de las geometrías, validos desde DC hasta el modo de operación en Rf para los nodos tecnológicos futuros. Dichos modelos se han extendido para analizar el ruido de alta frecuencia en estos diapositivos.
254

High Frequency Ultrasound RF Time Series Analysis for Tissue Characterization

NAJAFI YAZDI, MOHSEN 29 March 2012 (has links)
Ultrasound-based tissue characterization has been an active eld of cancer detection in the past decades. The main concept behind various techniques is that the returning ultrasound echoes carry tissue-dependent information that can be used to distinguish tissue types. Recently, a new paradigm for tissue typing has been proposed which uses ultrasound Radio Frequency (RF) echoes, recorded continuously from a xed location of the tissue, to extract tissue-dependent information. This is hereafter referred to as RF time series. The source of tissue typing information in RF time series is not a well known concept in the literature. However, there are two main hypotheses that describe the informativeness of variations in RF time series. Such information could be partly due to heat induction as a result of consistent eradiation of tissue with ultrasound beams which results in a virtual displacement in RF echoes, and partly due to the acoustic radiation force of ultrasound beams resulting in micro-vibration inside tissue. In this thesis, we further investigate RF time series signals, collected at high frequencies, by analyzing the properties of the RF displacements. It will be shown that such displacements exhibit oscillatory behavior, emphasizing on the possible micro-vibrations inside tissue, as well as linear incremental trend, indicating the e ect of heat absorbtion of tissue. i The main focus of this thesis is to study the oscillatory behavior of RF displace- ments in order to extract tissue-dependent features based on which tissue classi ca- tion is performed. Using various linear and nonlinear tools, we study the properties of such displacements in both frequency and time domain. Nonlinear analysis, based on the theory of dynamical systems, is used to study the dynamical and geometrical properties of RF displacements in the time domain. Using Support Vector Machine (SVM), di erent tissue typing experiments are performed to investigate the capability of the proposed features in tissue classi ca- tion. It will be shown that the combination of such features can distinguish between di erent tissue types almost perfectly. In addition, a feature reduction algorithm, based on principle component analysis (PCA), is performed to reduce the number of features required for a successful tissue classi cation. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-03-29 13:52:10.874
255

Measurements of radiation induced currents in RF coil conductors

Ghila, Andrei Dorin Unknown Date
No description available.
256

Characterization of Radiation Induced Current in RF coils of Linac-MR Systems

Burke, Benjamin Unknown Date
No description available.
257

RF crosstalk in InP based Transmission Lines

Khosravi Nahouji, Mahboobeh January 2014 (has links)
Currently two main tracks are considered for integration of photonic circuits. Silicon based integration may be more cost effective; however implementation of some functionalities like laser, is problematic. In contrast InP offers complete solution of photonic integration including laser diodes. Additionally, much higher speeds may be anticipated from InP based integration. As in the case of ordinary integrated circuits, attempts to increase degree (density) lead to undesired coupling-crosstalk between the components. Three types of cross coupling may be clearly distinguished: optical, RF(electric) and thermal. Each of them has its specifics, physical mechanisms and methods of analysis. Modeling RF crosstalk will be in the focus of this project. To drive active components, such as laser and photodiodes, conducting tracks are integrated with photonic components. In multichannel photonic IC chips these tracks become very dense leading to strong parasitic electrical couplings between them. This crosstalk becomes more problematic in high speed photonic IC chips where the frequency of the RF signals (modulation, detection) is in the range up to 10GHz and beyond. Thus modeling of the crosstalk between RF tracks (also between RF and DC) is of prime importance. This is the main task of the project. A further task is analysis of the crosstalk using developed models and considering designs allowing reduced cross coupling.
258

SiGe BiCMOS RF front-ends for adaptive wideband receivers

Saha, Prabir K. 27 August 2014 (has links)
The pursuit of dense monolithic integration and higher operating speed continues to push the integrated circuit (IC) fabrication technologies to their limits. The increasing process variation, associated with aggressive technology scaling, is having a negative impact on circuit yield in current IC technologies, and the problem is likely to become worse in the future. Circuit solutions that are more tolerant of the process variations are needed to fully utilize the benefits of technology scaling. The primary goal of this research is to develop high-frequency circuits that can deliver consistent performance even under the threat of increasing process variation. These circuits can be used to build ``self-healing" systems, which can detect process imperfections and compensate accordingly to optimize performance. In addition to improving yield, such adaptive circuits and systems can provide more robust and efficient solutions for a wide range of applications under varying operational and environmental conditions.Silicon-germanium (SiGe) BiCMOS technology is an ideal platform for highly integrated systems requiring both high-performance analog and radio-frequency (RF) circuits as well as large-scale digital functionality. This research is focused on designing circuit components for a high-frequency wideband self-healing receiver in SiGe BiCMOS technology. An adaptive image-reject mixer, low insertion-loss switches, a wideband low-noise amplifier (LNA), and a SiGe complementary LC oscillator were designed. Healing algorithms were developed, and automated self-healing of multiple parameters of the mixer was demonstrated in measurement. A monte-carlo simulation based methodology was developed to verify the effectiveness of the healing procedure. In summary, this research developed circuits, algorithms, simulation tools, and methods that are useful for building "self-healing" systems.
259

Tunable Filters and RF MEMS Variable Capacitors with Closed Loop Control

Zahirovic, Nino January 2011 (has links)
Multi-band and multi-mode radios are becoming prevalent and necessary in order to provide optimal data rates across a network with a diverse and spotty landscape of coverage areas (3G, HSPA, LTE, etc.). As the number of required bands and modes increases, the aggregate cost of discrete RF signal chains justi es the adoption of tunable solutions. Tunable fi lters are one of the pieces crucial to signal chain amalgamation. The main requirements for a tunable fi lter are high unloaded quality factor, wide tuning range, high tuning speed, high linearity, and small size. MEMS technology is the most promising in terms of tuning range, quality factor, linearity and size. In addition, a fi lter that maintains a constant passband bandwidth as the center frequency is tuned is preferred since the analog baseband processing circuitry tends to be tailored for a particular signal bandwidth. In this work, a novel design technique for tunable fi lters with controlled and predictable bandwidth variation is presented. The design technique is presented alongside an analysis and modeling method for predicting the final filter response during design optimization. The method is based on the well known coupling matrix model. In order to demonstrate the design and modeling technique, a novel coupling structure for stripline fi lters is presented that results in substantial improvements in coupling bandwidth variation over an octave tuning range when compared to combline and interdigitated coupled line fi lters. In order for a coupled resonator filter to produce an equal ripple Chebyshev response, each resonator of the fi lter must be tuned to precisely the same resonant frequency. Production tuned fi lters are routinely tuned in the lab and production environments by skilled technicians in order to compensate for manufacturing tolerances. However, integrated tunable filters cannot be tuned by traditional means since they are integrated into systems on circuit boards or inside front end modules. A fixed tuning table for all manufactured modules is inadequate since the required tuning accuracy exceeds the tolerance of the tuning elements. In this work, we develop tuning techniques for the automatic in-circuit tuning of tunable filters using scalar transmission measurement. The scalar transmission based techniques obviate the use of directional couplers. Techniques based on both swept and single frequency scalar transmission measurement are developed. The swept frequency technique, based on the Hilbert transform derived relative groupdelay, tunes both couplings and resonant frequencies while the single frequency technique only tunes the center frequency. High performance filters necessitate high resonator quality factors. Although fi lters are traditionally treated as passive devices, tunable fi lters need to be treated as active devices. Tuning elements invariably introduce non-linearities that limit the useful power handling of the tunable fi lter. RF MEMS devices have been a topic of intense research for many years for their promising characteristics of high quality factor and high power handling. Control and reliability issues have resulted in a shift from continuously tunable devices to discretely switched devices. However, fi lter tuning applications require fine resolution and therefore many bits for digital capacitor banks. An analog/digital hybrid tuning approach would enable the tuning range of a switched capacitor bank to be combined with the tuning resolution of an analog tunable capacitor. In this work, a device-level position control mechanism is proposed for piezoresistive feedback of device capacitance over the device's tuning range. It is shown that piezoresistve position control is ef ective at improving capacitance uncertainty in a CMOS integrated RF MEMS variable capacitor.
260

An Adjustable Impedance Matching Network Using Rf Mems Technology

Unlu, Mehmet 01 January 2003 (has links) (PDF)
This thesis presents design, modeling, and fabrication of an RF MEMS adjustable impedance matching network. The device employs the basic triple stub matching technique for impedance matching. It has three adjustable length stubs which are implemented using capacitively loaded coplanar waveguides. The capacitive loading of the stubs are realized using the MEMS switches which are evenly distributed over the stubs. There are 40 MEMS bridges on each stub whichare separated with &amp / #955 / /40 spacing making a total of 120 MEMS switches in the structure. The variability of the stub length is accomplished by closing the MEMS switch nearest to the required stub length, and making a virtual short circuit to ground. The device is theoretically capable of doing matching to every point on the Smith chart. The device is built on coplanar waveguide transmission lines. It has a center operating frequency of 10GHz, but because of its adjustability property it is expected to work in 1-40GHz range. It has dimensions of 8950 &times / 5720&micro / m2. This work is the continuation of the first national work on fabrication of RF MEMS devices. The device in this work is fabricated using the surface micromachining technology in the microelectronic facilities of Middle East Technical University.

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