• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 313
  • 126
  • 87
  • 45
  • 39
  • 35
  • 24
  • 24
  • 13
  • 8
  • 3
  • 3
  • 2
  • 2
  • 2
  • Tagged with
  • 907
  • 273
  • 191
  • 178
  • 111
  • 99
  • 89
  • 86
  • 80
  • 79
  • 77
  • 72
  • 70
  • 68
  • 68
  • 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.

Réalisation, étude et modélisation de diodes Schottky sur germanium intrinsèque.

Traore, Mahama Yves, January 1900 (has links)
Th. 3e cycle--Énerg. phys.--Grenoble--I.N.P., 1981. N°: D3 151.

Diode Schottky sur silicium amorphe hydrogéné : caractérisation électrique du matériau et application photovoltaïque.

Jousse, Didier, January 1900 (has links)
Th. doct.-ing.--Grenoble, I.N.P.G., 1979. N°: DI 85.

si/sige heterostructures: materials, physics, quantum functional devices and their integration with heterostructure bipolar transistors

Chung, Sung-Yong 22 November 2005 (has links)
No description available.

Study of the Avalanche Multiplication and Signal-to-Noise Power Ratio in the Ternary In<sub>x</sub>Ga<sub>1-x</sub>As Avalanche Photodiode

Wymer, Susan Lee 01 January 1979 (has links) (PDF)
Major advances in fiber optic transmissions have brought about a need for highly sensitive photodetectors. In order to detect this type of transmission, the photodetector must be able to detect one of the two low loss windows of the fiber optics transmission. The photodetector must also be characterized by a high gain and fast speed of response without generating excessive noise power. This report compares different types of high speed phodetectors with emphasis on the merits of using an avalanche photodiode. The report studies the avalanche multiplication and the signal-to-noise power ratio in the ternary InGaAs. The effects of the absorption coefficient, the depletion width, and the impurity concentration are studied. Finally, an optimization of the signal-to-noise power ratio is achieved by selecting the proper impurity concentration profile at suitable values of absorption coefficient and epitaxial width.

Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range

Elfergani, Issa T., Hussaini, Abubakar S., Abd-Alhameed, Raed, See, Chan H., Abusitta, M.M., Hraga, Hmeda I., Alhaddad, A.G., Rodriguez, Jonathan 22 March 2011 (has links)
Yes / A frequency tuned antenna has been designed to meet the coverage requirements of the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and a planar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lines with broadband characteristics. The handset represents the finite ground plane, and a varactor diode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtained by placing lumped capacitors, instead of the varactor, over the radiator. Good agreement is obtained between the predicted and measured input return loss, gain and radiation pattern over the tuned frequency range. / MSCRC

Modellierung, Charakterisierung und Design von PIN-Dioden zur Nutzung als ESD-Schutzstrukturen und Hochleistungsbauelementen

Scharf, Patrick 29 August 2022 (has links)
Mit der Entdeckung des Gleichrichter-Effekts 1873 wurde der theoretische Grundstein für die Halbleiter-Diode gelegt. Heutzutage sind Dioden auf nahezu allen elektronischen Schaltungen zu finden. Sie erfüllen dabei unterschiedlichste Aufgaben und finden Anwendung zum Beispiel als Gleichrichter, RF-Widerstand oder ESD-Schutzstruktur. Dioden basieren auf einem p/n-Übergang, welcher den Stromfluss in eine Richtung passieren lässt und in die andere Richtung sperrt. Bei PIN-Dioden wird zwischen der p-dotierten und der n-dotierten Zone noch ein intrinsisches bzw. niedrig dotiertes Gebiet eingefügt. Im Rahmen dieser Arbeit wurden Silizium- und GaAs- basierte PIN-Dioden für den Einsatz als ESD-Schutzstruktur und für Anwendungen in der Leistungselektronik untersucht. Mit Hilfe von TCAD-Simulationen wurden verschiedene Eigenschaften der PIN-Dioden unter Einwirkung eines ESD-Ereignisses analysiert. Die Bildung und Bewegung von Stromfilamenten konnte dabei beobachtet werden. Es stellte sich heraus, dass die Geometrie der Schutzdiode einen direkten Einfluss auf deren Lebensdauer hat. Es konnten Designvorschläge für ein optimiertes ESD-Schutzverhalten gemacht werden. Zur Validierung der Ergebnisse wurden verschiedene PIN-Dioden hergestellt und mittels TLP-Messung charakterisiert. Bei sehr schmalen Strukturgrößen konnten mehrere Spannungsabfälle beobachtet werden, was auf das Vorhandensein mehrerer Stromfilamente hindeutet. Diese Vermutung konnte anhand von TCAD-Simulationen bestätigt werden. Zur Analyse eines Layouts auf dessen ESD-Robustheit sind zeitintensive TCAD-Simulationen ungeeignet. Aus diesem Grund wurden auf Basis der TLP-Messungen und TCAD-Simulationen layoutabhängige Kompaktmodelle entwickelt. Diese ermöglichen eine schnelle Simulation der rückläufigen Kennlinie einer in Sperrrichtung vorgespannten PIN-Diode. Zusätzlich konnten die Bildung und Bewegung eines Stromfilaments nachgebildet werden. Im Hinblick auf Anwendungsmöglichkeiten in der Leistungselektronik, wurden Untersuchungen an GaAs-basierten PIN-Dioden durchgeführt. Diese zeichnen sich vor allem durch deutlich höhere Durchbruchspannungen aus. Mit TCAD-Simulationen und Hochspannungsmessungen wurden die Dioden charakterisiert. Aus den gewonnenen Erkenntnissen konnte ein analytisches Modell abgeleitet werden, was eine Optimierung der Diodenstruktur im Hinblick auf die Durchbruchspannung ermöglichte.

A Reflection Type Phase Shifter for iNET Phase Array Antenna Applications

Shrestha, Bikram 10 1900 (has links)
ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / In this article we present results from modeling and simulation of a L-band reflection type phase shifter (RTPS) that provides continuous phase shift of 0° to 360°. The RTPS circuit uses a 90º hybrid coupler and two reflective load networks consisting of varactor diodes and inductors. Proper design of 90° hybrid coupler is critical in realizing maximum phase shift. The RTPS circuit implemented on a Rogers Duroid substrate is large in size. We discuss methods to reduce the size of L-band RTPS.

A picosecond optoelectronic cross correlator using a gain modulated avalanche photodiode for measuring the impulse response of tissue

Kirkby, David Robert January 1999 (has links)
Human tissue is relatively transparent to light between 700 and 1000 nm in the near infrared (NIR). NIR spectroscopy is a technique that can measure non-invasively and safely, the optical properties of tissue. Several different types of spectroscopic instrumentation have currently been developed, ranging from simple continuous intensity systems, through to complex time and frequency resolved techniques. This thesis describes the development of a near infra-red time-resolved system, using an inexpensive avalanche photodiode (APD) detector and a microwave step recovery diode (SRD) in a novel way to implement a totally electronic crosscorrelator, with no moving parts. The aim of the work was to develop a simple instrument to monitor scattering changes in tissue during laser induced thermal therapy. The APD was gain-modulated by rapidly varying the bias voltage using electrical pulses generated by the SRD (120 ps full width half maximum (FWHM) and 8 V in amplitude). The resulting cross-correlator had a temporal resolution of 275 ps FWHM - significantly faster than the 750 ps FWHM of the APD when operating with a conventional fixed bias voltage. Spurious responses caused by the SRD were observed, which were removed by the addition of Schottky diodes on the SRD’s output, although this slightly degraded the system temporal resolution from 275 to 380 ps FWHM. The ability of the system to monitor scattering changes was tested using an IntralipidTM phantom containing infra-red absorbing dye. An 800 nm fibre coupled mode-locked (2 ps pulse width) laser source was used with the cross-correlator measuring the temporal point spread function (TPSF) at 5 to 30 mm away from the source fibre. Five different numerical algorithms to derive the scattering coefficient from the measured TPSF were compared. The optimum choice of algorithm was found to depend on whether absolute accuracy or minimum computation time is the most important consideration.

Optically pumped vertical external cavity surface emitting semiconductor lasers

Hoogland, Sjoerd January 2003 (has links)
No description available.

Rocket Motor Diagnostics using Tunable Diode Laser Spectroscopy for Chemically Non-Reacting Air/Water Vapor Mixture in Internal Flow

Carleton, Wesley 20 December 2013 (has links)
This research is for the implementation of non-intrusive measurement techniques in the study of high temperature pipe flow. A low pressure, laboratory scale hybrid rocket motor simulator was built to achieve high temperatures with various gases. A quartz test section was designed, built, and implemented into the existing test setup to accommodate the laser beam of the existing Tunable Diode Laser Absorption Spectrometer (TDLAS) system which was designed to observe water vapor. A super-heated water vapor injector was designed to obtain the desired water vapor concentrations. Flow characteristics were simultaneously recorded using the existing TDLAS system and the DAQ system for temperatures for later comparison. A numerical study using a commercial CFD package was used to predict the flow characteristics at certain locations for experimental comparison. Based on this study, it is concluded that the TDLAS can be used to make real time temperature measurements of heated internal gas flows.

Page generated in 0.0409 seconds