• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 6
  • 2
  • 2
  • Tagged with
  • 27
  • 27
  • 27
  • 8
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 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.
21

Design och implementering av enhandsburen RFID-läsare / Design and implementation of a handheld RFID-reader

Nordström, Edward, Hollander, Johan January 2008 (has links)
<p>Radio frequency identification (RFID) is a versatile wireless technology usedworldwide. The fields of applications are many and its popularity constantlygrows due to smaller in size, better and less expensive components. RFID isused to identify, track or share information about an object using radio waves.</p><p>This master thesis describes the process of designing and implementing ahandheld UHF RFID reader. The goal was to, based on a UHF RFID-chipdesign a fully functional, small in size and power efficient device. Amicrocontroller provides the user interface and is also used to control theRFID-chip and a Bluetooth device. A Bluetooth- and GPRS-compatible mobilephone will be used to forward data to a server connected to the Internet. Allparts of the design are described, such as the printed circuit board design aswell as the software for the micro controller and the mobile phone.</p><p>Because the extent of this thesis it is neither possible nor necessary to dig toodeep into the Bluetooth- or GPRS-protocol. The focus will be on designingsoftware and hardware for the handheld unit.</p> / <p>Radio frekvens identifiering (RFID) är en mångsidig trådlös teknik somanvänds över hela världen. Områdena där tekniken används är många och dess popularitet växer konstant tack vare mindre storlek, bättre och billigarekomponenter. RFID används för att identifiera, spåra eller dela med siginformation om ett objekt med radiovågor.</p><p>Det här examensarbetet beskriver processen av design och implementering aven handburen UHF RFID läsare. Målet har varit att, baserat på ett UHF-RFIDchip, designa en fullt fungerande, liten och strömsnål enhet. En microcontroller förser dels användaren med ett användargränssnitt och sköter delskommunikationen med RFID chip och en blåtandsmodul. En blåtands- ochGPRS- eller 3G-kompatibel mobiltelefon används for att skicka vidare data tillen server kopplad till Internet. Alla delar av designen är beskrivna, så som PCB design, mjukvara för micro controllern och mobiltelefonen.</p><p>På grund av omfattningen av det här examensarbetet så har det inte varitmöjligt eller nödvändigt att gräva för djupt i Blåtands- eller GPRS/3Gprotokollen. Fokus är på att designa hårdvara och mjukvara för den handhållna enheten.</p>
22

High Frequency Characterization and Modeling of SiGe Heterojunction Bipolar Transistors

Malm, B. Gunnar January 2002 (has links)
No description available.
23

Advanced Techniques for Multipactor Testing

Monerris Belda, Óscar 18 April 2023 (has links)
[ES] En los últimos años han proliferado los nuevos sistemas de satélites, sobre todo las grandes constelaciones en las órbitas terrestres bajas. Casi todos los satélites transmiten señales digitales con diversas modulaciones y niveles de potencia. Y no sólo eso, el modelo de negocio exige un rápido despliegue de los satélites, lo que impone enormes restricciones a los proveedores de equipos de carga útil de microondas. Un área de riesgo clave para estos equipos sigue siendo la avería del multipactor bajo niveles de potencia de moderados a altos. Debido a la aleatoriedad inherente al fenómeno multipactor, los clientes tienden a añadir márgenes de diseño adicionales para los componentes de microondas de alta potencia. Esto se traduce en costes más elevados, dispositivos más voluminosos y más tiempo para las pruebas. A partir de la experiencia personal realizando ensayos de multipactor, la principal motivación del trabajo descrito en la tesis ha sido emprender una revisión exhaustiva de este fenómeno y desarrollar capacidades de ensayo multipactor de vanguardia. Proporcionar medios para la prueba rápida de multipactores bajo una variedad de señales moduladas de banda ancha. La tesis demuestra que las modulaciones analógicas y digitales tienen un impacto significativo en el umbral multipactor. También se analizan los regímenes multipactor a corto y largo plazo, regímenes que, en algunos casos, presentan umbrales multipactor muy diferentes para el mismo hueco crítico. La necesidad de reducir el peso de la carga útil de microondas convierte a la multiportadora en una excelente opción para los diseñadores. Al encaminar varias señales a través del mismo dispositivo, el peso de la carga útil se reduce drásticamente. Las soluciones comerciales para pruebas multicarrier no son adecuadas debido a los altos niveles de potencia requeridos. Se presentan varias estrategias para implementar bancos de pruebas multiportadora con parámetros controlables. Los resultados demuestran que la señal generada es precisa y estable en el tiempo. Por último, se propone un novedoso sistema de detección de multipactores para hacer frente a la detección de multipactores cuando se utilizan señales moduladas y multiportadora de cualquier ancho de banda. Este método tiene la misma sensibilidad que el conocido anulador de microondas para señales de onda continua y la supera para señales moduladas. El procesamiento digital de señales utilizado para detectar los patrones multipactor proporciona un método de detección totalmente autónomo. / [CA] En els darrers anys han proliferat els nous sistemes de satèl·lits, sobretot les grans constel·lacions a les òrbites terrestres baixes. Gairebé tots els satèl·lits transmetten dades digitals amb diverses modulacions i nivells de potència. I no només això, el model de negoci exigeix un ràpid desplegament dels satèl·lits, cosa que imposa enormes restriccions als proveïdors de càrrega útil de microones. Una àrea de risc clau per a aquests equips continua sent la descarrega de multipactor sota nivells de potència de moderats a alts. A causa de l'aleatorietat inherent al fenomen multipactor, els clients tendeixen a afegir marges de disseny addicionals per als components de microones d'alta potència. Això es tradueix en costos més elevats, dispositius més voluminosos i més temps per a les proves. A partir de l'experiència personal realitzant assajos de multipactor, la motivació principal del treball descrit a la tesi ha estat emprendre una revisió exhaustiva d'aquest fenomen i desenvolupar capacitats d'assaig multipactor d'avantguarda. Proporcionar mitjans per a la prova ràpida de multipactors sota una varietat de senyals modulats de banda ampla. La tesi demostra que les modulacions analògiques i digitals tenen un impacte significatiu al llindar multipactor. També s'analitzen els règims multipactor a curt i llarg termini, règims que, en alguns casos, presenten llindars multipactor molt diferents per al buit crític mateix. La necessitat de reduir el pes de la càrrega útil de microones fa de la transmissií multiportadora en una excel·lent opció per als dissenyadors. Encaminant diverses senyals a través del mateix dispositiu, el pes de la càrrega útil es redueix dràsticament. Les solucions comercials per a proves multicarrier no són adequades a causa dels alts nivells de potència requerits. Es presenten diverses estratègies per implementar bancs de proves multiportadora amb paràmetres controlables. Els resultats demostren que el senyal amb què s'alimenta el dispositiu sotmès a proves és precís i estable en el temps. Finalment, es proposa un nou sistema de detecció de multipactors per fer front a la detecció de multipactors quan s'utilitzen senyals modulats i multiportadors de qualsevol amplada de banda. Aquest mètode té la mateixa sensibilitat que el conegut anul·lador de microones per a senyals d'ona contínua i la supera per a senyals modulats. El processament digital de senyals utilitzat per detectar els patrons multiactor proporciona un mètode de detecció totalment autònom. / [EN] In the recent past, there has been a proliferation of new satellite systems, especially the large constellations in the Low Earth Orbits (LEOs). Nearly all satellites now carry digital traffic with a variety of modulations and power levels. Not only that, the business model requires rapid deployment of satellites, putting enormous constraints for the suppliers of microwave payload hardware. A key risk area for such equipment remains the multipactor breakdown under moderate to high power levels. Owing to the inherent randomness of the multipactor phenomenon, customers tend to add extra design margins for the high power microwave components. This results in higher costs, bulkier devices and longer time for testing. Based on personal experience in multipactor testing, the prime motivator for the work described in the thesis has been to undertake a comprehensive review of this phenomenon and develop cutting edge multipactor test capabilities, providing means for the rapid multipactor testing under a variety of wide-band modulated signals. The thesis dissertation shows that analog and digital modulations have a significant impact in the multipactor threshold. The short and long-term multipactor regimes are also analyzed, regimes that, in some cases, have very different multipactor thresholds for the same critical gap. The need to reduce the microwave payload weight by using multicarriers in a single transponder provides an excellent option for designers. By routing several signals through the same device, the payload weight is dramatically reduced. Commercial solutions for multicarrier testing are not suitable because of the high power levels required. Several strategies to implement multipactor test benches with controllable parameters are presented. Results prove that the signal being fed to the device under tests is accurate and stable over time. Finally, a novel multipactor detection system is proposed to cope with multipactor detection when modulated and multicarrier signals of any bandwidth are used. This method has the same sensitivity as the well known microwave nulling for continuous wave signals and surpasses it for modulated signals. The digital signal processing used to detect the multipactor patterns provides a full autonomous detection method. / Monerris Belda, Ó. (2023). Advanced Techniques for Multipactor Testing [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192786
24

Efficient radio frequency power amplifiers for wireless communications

Cui, Xian 10 December 2007 (has links)
No description available.
25

Analyse et caractérisation des couplages substrat et de la connectique dans les circuits 3D : Vers des modèles compacts / Analysis and characterization of substrate and connection couplings in 3D circuits : Towards compact models

Sun, Fengyuan 19 July 2013 (has links)
L’intégration 3D est la solution technologique la plus prometteuse pour suivre le niveau d’intégration dictée par la loi de Moore (cf. more than Moore, versus more Moore). Elle entraine des travaux de recherche importants depuis une douzaine d’années. Elle permet de superposer différents circuits et composants dans un seul boitier. Son principal avantage est de permettre une association de technologies hétérogènes et très spécialisées pour la constitution d’un système complet, tout en préservant un très haut niveau de performance grâce à des connexions très courtes entre ces différents circuits. L’objectif de ce travail est de fournir des modélisations cohérentes de via traversant, ou/et de contacts dans le substrat, avec plusieurs degrés de finesse/précision, pour permettre au concepteur de haut niveau de gérer et surtout d’optimiser le partitionnement entre les différentes strates. Cette modélisation passe par le développement de plusieurs vues à différents niveaux d’abstraction: du modèle physique au modèle « haut niveau ». Elle devait permettre de répondre à différentes questions rencontrées dans le processus de conception :- le modèle physique de via basé sur une simulation électromagnétique 2D ou 3D (solveur « éléments finis ») est utilisé pour optimiser l’architecture du via (matériaux, dimensions etc.) Il permet de déterminer les performances électriques des via, notamment en haute fréquence. Les simulations électromagnétiques permettent également de quantifier le couplage entre via adjacents. - le modèle compact analytique de via et de leur couplage, basé sur une description de type ligne de transmission ou noyaux de Green, est utilisé pour les simulations au niveau bloc, ainsi que des simulations de type Spice. Les modèles analytiques sont souvent validés par rapport à des mesures et/ou des modèles physiques. / The 3D integration is the most promising technological solution to track the level of integration dictated by Moore's Law (see more than Moore, Moore versus more). It leads to important research for a dozen years. It can superimpose different circuits and components in one box. Its main advantage is to allow a combination of heterogeneous and highly specialized technologies for the establishment of a complete system, while maintaining a high level of performance with very short connections between the different circuits. The objective of this work is to provide consistent modeling via crossing, and / or contacts in the substrate, with various degrees of finesse / precision to allow the high-level designer to manage and especially to optimize the partitioning between the different strata. This modelization involves the development of multiple views at different levels of abstraction: the physical model to "high level" model. This would allow to address various issues faced in the design process: - The physical model using an electromagnetic simulation based on 2D or 3D ( finite element solver ) is used to optimize the via (materials, dimensions etc..) It determines the electrical performance of the via, including high frequency. Electromagnetic simulations also quantify the coupling between adjacent via. - The analytical compact of via their coupling model, based on a description of transmission line or Green cores is used for the simulations at the block level and Spice type simulations. Analytical models are often validated against measurements and / or physical models.
26

Low Power And Low Spur Frequency Synthesizer Circuit Techniques For Energy Efficient Wireless Transmitters

Manikandan, R R 09 1900 (has links) (PDF)
There has been a huge rise in interest in the design of energy efficient wireless sensor networks (WSN) and body area networks (BAN) with the advent of many new applications over the last few decades. The number of sensor nodes in these applications has also increased tremendously in the order of few hundreds in recent years. A typical sensor node in a WSN consists of circuits like RF transceivers, micro-controllers or DSP, ADCs, sensors, and power supply circuits. The RF transmitter and receiver circuits mainly the frequency synthesizers(synthesis of RF carrier and local oscillator signals in transceivers) consume a significant percentage of its total power due to its high frequency of operation. A charge-pump phase locked loop (CP-PLL) is the most commonly used frequency synthesizer architecture in these applications. The growing demands of WSN applications, such as low power consumption larger number of sensor nodes, single chip solution, and longer duration operation presents several design challenges for these transmitter and frequency synthesizer circuits in these applications and a few are listed below, Low power frequency synthesizer and transmitter designs with better spectral performance is essential for an energy efficient operation of these applications. The spurious tones in the frequency synthesizer output will mix the interference signals from nearby sensor nodes and from other interference sources present nearby ,to degrade the wireless transmitter and receiver performance[1]. With the increased density of sensor nodes (more number of in-band interference sources) and degraded performance of analog circuits in the nano-meter CMOS process technologies, the spur reduction techniques are essential to improve the performance of frequency synthesizers in these applications. A single chip solution of sensor nodes with its analog and digital circuits integrated on the same die is preferred for its low power, low cost, and reduced size implementation. However, the parasitic interactions between these analog and digital sub-systems integrated on a common substrate, degrade the spectral performance of frequency synthesizers in these implementations[2]. Therefore, techniques to improve the mixed signal integration performance of these circuits are in great demand. In this thesis, we present a custom designed energy efficient 2.4 GHz BFSK/ASK transmitter architecture using a low power frequency synthesizer design technique taking advantage of the CMOS technology scaling benefits. Furthermore, a few design guidelinesandsolutionstoimprovethespectralperformanceoffrequency synthesizer circuits and in-turn the performance of transmitters are also presented. The target application being short distance, low power, and battery operated wireless communication applications. The contributions in this thesis are, Spectral performance improvement techniques The CP mismatch current is a dominant source of reference spurs in the nano-meter CMOS PLL implementations due to its worsened channel length modulation effect [3]. In this work, we present a CP mismatch current calibration technique using an adaptive body bias tuning of its PMOS transistors. Chip prototype of 2.4 GHzCP-PLLwith the proposed CP calibration technique was fabricated in UMC 0.13 µm CMOS process. Measurements show a CP mismatch current of less than 0.3 µA(0.55 %) using the proposed calibration technique over the VCO control voltage range 0.3 to 1 V. The closed loop PLL measurements using the proposed technique exhibited a 9dB reduction in the reference spur levels across the PLL output frequency range 2.4 -2.5 GHz. The parasitic interactions between analog and digital circuits through the common substrate severely affects the performance of CP-PLLs. In this work, we experimentally demonstrate the effect of periodic switching noise generated from the digital buffers on the performance of charge-pump PLLs. The sensitivity of PLL performance metrics such as output spur level, phase noise, and output jitter are monitored against the variations in the properties of a noise injector digital signal. Measurements from a 500 MHz CP-PLL shows that the pulsed noise injection with the duty cycle of noise injector signal reduced from 50% to 20%, resulted in a 12.53 dB reduction in its output spur level and a 107 ps reduction in its Pk-Pk deterministic period jitter performance. Low power circuit techniques A low power frequency synthesizer design using a digital frequency multiplication technique is presented. The proposed frequency multiply by 3 digital edge combiner design having a very few logic gates, demonstrated a significant reduction in the power consumption of frequency synthesizer circuits, with an acceptable spectral performance suitable for these relaxed performance applications. A few design guidelines and techniques to further improve its spectral performance are also discussed and validated through simulations. Chip prototypes of 2.4 GHz CP-PLLs with and without digital frequency multiplier circuits are fabricated in UMC 0.13 µm CMOS process. The 2.4 GHz CP-PLL using the proposed digital frequency multiplication technique (10.7 mW) consumed a much reduced power compared to a conventional implementation(20.3 mW). A custom designed, energy efficient 2.4 GHz BFSK/ASK transmitter architecture using the proposed low power frequency synthesizer design technique is presented. The transmitter uses a class-D power amplifier to drive the 50Ω antenna load. Spur reduction techniques in frequency synthesizers are also used to improve the spectral performance of the transmitter. A chip prototype of the proposed transmitter architecture was implemented in UMC0.13 µm CMOS process. The transmitter consume14 mA current from a 1.3V supply voltage and achieve improved energy efficiencies of 0.91 nJ/bit and 6.1 nJ/bit for ASK and BFSK modulations with data rates 20Mb/s & 3Mb/s respectively.
27

Radio wave imaging using Ultra-Wide Band Spectrum Antennas for Near-Field Applications. Design, Development, and Measurements of Ultra-Wideband Antenna for Microwave Near-Field Imaging Applications by applying Optimisation Algorithms

Danjuma, Isah M. January 2020 (has links)
The emergence of Ultra-wideband (UWB) technology application has yielded tremendous and vital impacts in the field of microwave wireless communications. These applications include military radar imaging, security screening, and tumour detection, especially for early detection of breast cancer. These indicators have stimulated and inspired many researchers to make the best use of this promising technology. UWB technology challenges such as antenna design, the problem of imaging reconstruction techniques, challenges of severe signal attenuation and dispersion in high loss material. Others are lengthy computational time demand and large computer memory requirements are prevalent constraints that need to be tackled especially in a large scale and complex computational electromagnetic analysis. In this regard, it is necessary to find out recently developed optimisation techniques that can provide solutions to these problems. In this thesis, designing, optimisation, development, measurement, and analysis of UWB antennas for near-field microwave imaging applications are considered. This technology emulates the same concept of surface penetrating radar operating in various forms of the UWB spectrum. The initial design of UWB monopole antennas, including T-slots, rectangular slots, and hexagonal slots on a circular radiating patch, was explicitly implemented for medical imaging applications to cover the UWB frequency ranging from 3.1 GHz to 10.6 GHz. Based on this concept, a new bow-tie and Vivaldi UWB antennas were designed for a through-the-wall imaging application. The new antennas were designed to cover a spectrum on a lower frequency ranging from 1 GHz - 4 GHz to ease the high wall losses that will be encountered when using a higher frequency range and to guarantee deeper penetration of the electromagnetic wave. Finally, both simulated and calculated results of the designed, optimised antennas indicate excellent agreement with improved performance in terms of return loss, gain, radiation pattern, and fidelity over the entire UWB frequency. These breakthroughs provided reduced computational time and computer memory requirement for useful, efficient, reliable, and compact sensors for imaging applications, including security and breast cancer detection, thereby saving more lives. / Tertiary Education Trust Fund (TET Fund) Supported by the Nigerian Defence Academy (NDA)

Page generated in 0.0511 seconds