119 research outputs found
Multifunction Transceiver Architecture and Technology for Future Wireless Systems
RÉSUMÉ Depuis la toute première transmission sans fil, les ondes radiofréquences ont été progressivement mises en valeur et exploitées dans un nombre de plus en plus important d'applications. Parmi toutes ces applications, la détection et la télécommunication sont sans doute les plus indispensables de nos jours. Il existe un grand nombre d’utilisations des radiofréquences, incluant les transports intelligents pour lesquels les véhicules doivent être équipés à la fois de radars et de dispositifs de communication afin d’être capables de détecter l'environnement ainsi que de réaliser la communication avec d'autres unités embarquées. La technologie émergente 5G est un autre exemple pour lequel plusieurs capteurs et radios devraient être capables de coopérer de manière autonome ou semi-autonome. Les principes de fonctionnement des systèmes radars et radio sont toutefois différents. Ces différences fondamentales peuvent entraîner l'utilisation de différentes architectures de traitement du signal et d'émetteur-récepteur, ce qui peut poser des problèmes pour l'intégration de toutes les fonctions requises au sein d'une seule et même plate-forme. En dehors de cela, certaines applications requièrent plusieurs fonctions simultanément dans un même dispositif. Par exemple, les systèmes de détection d'angle d'arrivée 2D nécessitent d'estimer l'angle d'arrivée (AOA) du faisceau entrant dans les plans horizontal et vertical simultanément. La communication radio multi-bandes et multi-modes est un autre exemple pour lequel un système radio doit être capable de communiquer dans plusieurs bandes de fréquences et dans plusieurs modes, par exemple, un duplexage en fonction de la fréquence ou du temps. À première vue, on peut penser que l'assemblage de plusieurs dispositifs distincts n'est pas la meilleure solution en ce qui concerne le coût, la simplicité et la fonctionnalité. Par conséquent, une direction de recherche consiste à proposer une architecture d'émetteur-récepteur unifiée et compacte plutôt qu’une plate-forme assemblant de multiples dispositifs distincts. C’est cette problématique qui est spécifiquement abordée dans ce travail. Selon les fonctions à intégrer dans un seul et unique système multifonctionnel, la solution peut traiter plusieurs aspects simultanément. Par exemple, toute solution réalisant l'intégration de fonctions liées au radar et à la radio devrait traiter deux aspects principaux, à savoir : la forme d'onde opérationnelle et l'architecture frontale RF.----------ABSTRACT Since the very early wireless transmission of radiofrequency signals, it has been gradually flourished and exploited in a wider and wider range of applications. Among all those applications of radio technology, sensing and communicating are undoubtedly the most indispensable ones. There are a large number of practical scenarios such as intelligent transportations in which vehicles must be equipped with both radar and communication devices to be capable of both sensing the environment and communication with other onboard units. The emerging 5G technology can be another important example in which multiple sensors and radios should be capable of cooperating with each other in an autonomous or semi-autonomous manner. The operation principles of these radar and radio devices are different. Such fundamental differences can result in using different operational signal, distinct signal processing, and transceiver architectures in these systems that can raise challenges for integration of all required functions within a single platform. Other than that, there exist some applications where several functions of a single device (i.e. sensor or radio) are required to be executed simultaneously. For example, 2D angle-of-arrival detection systems require estimating the angle of arrival (AOA) of the incoming beam in both horizontal and vertical planes at the same time. Multiband and multimode radio communication is another example of this kind where a radio system is desired to be capable of communication within several frequency bands and in several modes, e.g., time or frequency division duplexing. At a first glance, one can feel that the mechanical assembling of several distinct devices is not the best solution regarding the cost, simplicity and functionality or operability. Hence, the research attempt in developing a rather unified and compact transceiver architecture as opposed to a classical platform with assembled multiple individual devices comes out of horizon, which is addressed specifically in this work.
Depending on the wireless functions that are to be integrated within a single multifunction system, the solution should address multiple aspects simultaneously. For instance, any solution for integrating radar and radio related functions should be able to deal with two principal aspects, namely operational waveform and RF front-end architecture. However, in some other above- mentioned examples such as 2D DOA detection system, identical operational waveform may be used and the main challenge of functional integration would pertain to a unification of multiple mono-functional transceivers
Simultaneous Wireless Power Transmission and Data Communication
RÉSUMÉ : Le développement rapide des systèmes électroniques sans fil de faible consommation de puissance a conduit à d'innombrables activités de recherche dans le cadre de la faisabilité d'une alimentation à distance ou sans fil de ces systèmes. Par conséquent, la transmission d'énergie sans fil (WPT), qui est développé comme une technique prometteuse pour alimenter les appareils électroniques à longue distance et permettre la conception et le développement de systèmes auto-alimentés, est devenue un centre d'intérêt depuis de nombreuses années. Les antennes de redressement connues sous le nom de rectennas, sont les éléments les plus importants de transmission à longue portée d'énergie sans fil. L'efficacité de rectennas dépend essentiellement de leurs antennes et les circuits redresseurs associés. Par conséquent, pour concevoir une antenne redresseuse à haut rendement qui garantit la qualité d'un système WPT, plus d'attention devrait être concentré sur l’étude, l'analyse et le développement des antennes à gain élevé et redresseurs à haute efficacité de conversion RF-DC. Dans la littérature, différentes configurations de circuit antenne redresseuse, opérant principalement à basse fréquence tels que 2,45 GHz et 5,8 GHz, ont été largement étudiés. Cependant, il existe quelques études rapportées à la fréquence à ondes millimétriques, bien que les avantages de plus petite taille et l'efficacité du système global plus élevée pour la transmission à longue distance peuvent être obtenus à la fréquence à ondes millimétriques. D'autre part, les circuits rectennas peuvent tout simplement récupérer l'énergie, mais ils ne peuvent pas décoder le signal transmis à des fins de communication. Cependant, la transmission de données est une condition essentielle dans les systèmes de communication sans fil. Par conséquent, si la capacité de détection et de traitement du signal peut être ajoutée à une architecture de rectenna, alors, un récepteur de communication sans fil transmettant simultanément de l'énergie et de données peut être réalisé. La réalisation d'un tel système peut être considérée comme une approche prometteuse pour la prochaine génération de systèmes de communication auto-alimentés.
Cette thèse de doctorat vise à examiner et à démontrer un système de transmission d'énergie sans fil et également un récepteur avec la capacité de récupérer l’énergie et de données de communication simultanément fonctionnant aux fréquences à ondes millimétriques. Pour atteindre ces objectifs, différentes structures de circuit redresseurs sont étudiés, conçus et mesurés expérimentalement.----------ABSTRACT The rapid development of low power wireless electronic systems has led to countless research activities in connection with the feasibility of a remote or wireless powering of those systems. Therefore, wireless power transmission (WPT) has become a focal point of interest since many years, which is being developed as a promising technique, for powering electronic devices over distance and for enabling the design and development of self-powered systems. The rectifying antennas known as rectennas are the most important elements in long-range wireless power transmission. The efficiency of rectennas mainly depends on their antennas and the related rectifier circuits. Therefore, to design a high-efficiency rectenna that guarantees the quality of a WPT system, more focus should be concentrated on the investigation, analysis and development of high-gain antennas and performance-driven rectifiers with reference to high RF-to-DC conversion efficiency. In the literature, different configurations of rectenna circuit, mainly operating at low frequency such as 2.45 GHz and 5.8 GHz, have been widely investigated. However, there are just a few reported studies at millimeter-wave frequency although the advantages of more compact size and higher overall system efficiency for long distance transmission can be obtained at millimeter-wave frequency. On the other hand, rectenna circuits can just scavenge energy and they cannot decode the transmitted signal for communication purpose. However, the data transmission is an essential requirement of wireless communication systems. Therefore, if the ability of signal detection and processing can be added to a rectenna architecture then a receiver with simultaneous wireless power transmission and data communication can be realized. The realization of such a system can be considered as a promising approach for the next generation of self-powered communication systems. This PhD dissertation aims to investigate and demonstrate a system of wireless power transmission and also a receiver with the capability of simultaneous wireless energy harvesting and data communication operating at up-microwave and millimeter-wave frequency
Quantum-based security in optical fibre networks
Electronic communication is used everyday for a number of different applications.
Some of the information transferred during these communications can be private
requiring encryption and authentication protocols to keep this information secure.
Although there are protocols today which provide some security, they are not
necessarily unconditionally secure. Quantum based protocols on the other hand, can
provide unconditionally secure protocols for encryption and authentication.
Prior to this Thesis, only one experimental realisation of quantum digital signatures had
been demonstrated. This used a lossy photonic device along with a quantum memory
allowing two parties to test whether they were sent the same signature by a single
sender, and also store the quantum states for measurement later. This restricted the
demonstration to distances of only a few metres, and was tested with a primitive
approximation of a quantum memory rather than an actual one. This Thesis presents an
experimental realisation of a quantum digital signature protocol which removes the
reliance on quantum memory at the receivers, making a major step towards practicality.
By removing the quantum memory, it was also possible to perform the swap and
comparison mechanism in a more efficient manner resulting in an experimental
realisation of quantum digital signatures over 2 kilometres of optical fibre.
Quantum communication protocols can be unconditionally secure, however the
transmission distance is limited by loss in quantum channels. To overcome this loss in
conventional channels an optical amplifier is used, however the added noise from these
would swamp the quantum signal if directly used in quantum communications.
This Thesis looked into probabilistic quantum amplification, with an experimental
realisation of the state comparison amplifier, based on linear optical components and
single-photon detectors. The state comparison amplifier operated by using the wellestablished
techniques of optical coherent state comparison and weak subtraction to
post-select the output and provide non-deterministic amplification with increased
fidelity at a high repetition rate. The success rates of this amplifier were found to be
orders of magnitude greater than other state of the art quantum amplifiers, due to its lack
of requirement for complex quantum resources, such as single or entangled photon
sources, and photon number resolving detectors
Harmonic mixer analysis and design
Thesis (MScEng) -- Stellenbosch University, 2002.Some digitised pages may appear illegible due to the condition of the original hard copy.ENGLISH ABSTRACT: Harmonic mixers are capable of extended frequency operation by mixing with a harmonic of the
LO (local oscillator) signal, eliminating the need for a high frequency, high power LO. Their
output spectra also have certain characteristics that make them ideal for a variety of applications.
The operation of the harmonic mixer is investigated, and the mixer is analyzed using an
extension of the classic mixer theory. The synthesis of harmonic mixers is also investigated, and
a design procedure is proposed for the design and realization of a variety of harmonic mixers.
This design procedure is evaluated with the design and realization of two harmonic mixers, one
in X-band and the other in S-band. Measurements suggest that the procedure is successful for the
specific applications.AFRIKAANSE OPSOMMING: Harmoniese mengers kan by hoer frekwensies gebruik word as gewone mengers deurdat hulle
gebruik maak van ‘n harmoniek van die LO. ‘n Hoe-frekwensie, hoe-drywing LO word dus nie
benodig nie. Die mengers se uittreespektra het ook ‘n aantal karakteristieke wat hulle goeie
kandidate maak vir ‘n verskeidenheid van toepassings. Die werking van die harmoniese menger
word ondersoek deur uit te brei op die klassieke menger-teorie. Die ontwerp van die harmoniese
menger word vervolgens ondersoek, waama ‘n ontwerpsprosedure voorgestel word vir die
ontwerp van ‘n verskeidenheid van harmoniese mengers. Hierdie prosedure word getoets met die
ontwerp en realisering van twee harmoniese mengers, een in X-band en die ander in S-band.
Vanuit die metings is dit duidelik dat die ontwerpsprosedure geslaagd is vir die spesifieke geval
A Novel 183GHz Subharmonic Schottky Diode Mixer
PhDThe technique of microwave .
limb sounding -from space
represents a very powerful tool for determining the atmospheric
processes involved in ozone depletion, the greenhouse effect, acid
rain, etc.. Unfortunately, the technology involved in producing
millimetric and submillimetric devices is highly complex, and
miniature. The power levels and environmental conditions
existing aboard spacecraft in present 'use, 5 differ from those
required by the low noise heterodyne receivers employed by the
Radio Astronomy community. Therefore, great effort has been
spent in the design of radiometers with limited power and weight
requirements, so that they can withstand the rigours of launch
and operation in space.
This thesis describes the design and construction of a
subharmonically pumped, double diode mixer which is now used
in an airborne atmospheric radiometer. The mixer power
requirement and rugged nature make it an ideal option for space
operation. The assembly of the millimetric circuit required the
development, of novel techniques which enabled the incorporation
of discrete circuit elements onto a single quartz substrate. This
allowed the physical testing of the millimetric circuit
independently of the RF block.
A detailed investigation into the `whiskering' technique was
carried out. It was thus possible to pinpoint errors that had
previously occurred in assembly and which had resulted in the
failure of a space flight device. With the adoption of quantified
procedures, devices constructed using the `whiskering' technique
were shown to be considerably more resilient than had previously
been thought.
The performance of the mixer is comparable with other
designs using Schottky diodes at room temperature (-1200K DSB)
and the local oscillator power requirement is easily met with a
single solid state source.
A simple theoretical analysis using the Seigel and Kerr
program was undertaken in conjunction with RF measurements
performed on a 65X scale model to determine steps required for
further improvement.Marconi Space Systems.
United Kingdom Meteorological Office and the SER
Recommended from our members
NBS monograph
From Introduction: "The purpose of this guide is to describe, discuss, and analyze methods of measuring the average noise factor and average effective input noise temperature of an electronic transducer.
Data security in photonic information systems using quantum based approaches
The last two decades has seen a revolution in how information is stored and transmitted
across the world. In this digital age, it is vital for banking systems, governments and
businesses that this information can be transmitted to authorised receivers quickly and
efficiently. Current classical cryptosystems rely on the computational difficulty of
calculating certain mathematical functions but with the advent of quantum computers,
implementing efficient quantum algorithms, these systems could be rendered insecure
overnight. Quantum mechanics thankfully also provides the solution, in which
information is transmitted on single-photons called qubits and any attempt by an
adversary to gain information on these qubits is limited by the laws of quantum
mechanics.
This thesis looks at three distinct different quantum information experiments. Two of
the systems describe the implementation of distributing quantum keys, in which the
presence of an eavesdropper introduces unavoidable errors by the laws of quantum
mechanics. The first scheme used a quantum dot in a micropillar cavity as a singlephoton
source. A polarisation encoding scheme was used for implementing the BB84,
quantum cryptographic protocol, which operated at a wavelength of 905 nm and a clock
frequency of 40 MHz. A second system implemented phase encoding using asymmetric
unbalanced Mach-Zehnder interferometers, with a weak coherent source, operating at a
wavelength of 850 nm and pulsed at a clock rate of 1 GHz. The system used
depolarised light propagating in the fibre quantum channel. This helps to eliminate the
random evolution of the state of polarisation of photons, as a result of stress induced
changes in the intrinsic birefringence of the fibre. The system operated completely
autonomously, using custom software to compensate for path length fluctuations in the
arms of the interferometer and used a variety of different single-photon detector
technologies. The final quantum information scheme looked at quantum digital
signatures, which allows a sender, Alice, to distribute quantum signatures to two parties,
Bob and Charlie, such that they are able to authenticate that the message originated
from Alice and that the message was not altered in transmission
Adaptive Suppression of Interfering Signals in Communication Systems
The growth in the number of wireless devices and applications underscores the need for characterizing and mitigating interference induced problems such as distortion and blocking. A typical interference scenario involves the detection of a small amplitude signal of interest (SOI) in the presence of a large amplitude interfering signal; it is desirable to attenuate the interfering signal while preserving the integrity of SOI and an appropriate dynamic range. If the frequency of the interfering signal varies or is unknown, an adaptive notch function must be applied in order to maintain adequate attenuation. This work explores the performance space of a phase cancellation technique used in implementing the desired notch function for communication systems in the 1-3 GHz frequency range. A system level model constructed with MATLAB and related simulation results assist in building the theoretical foundation for setting performance bounds on the implemented solution and deriving hardware specifications for the RF notch subsystem devices. Simulations and measurements are presented for a Low Noise Amplifer (LNA), voltage variable attenuators, bandpass filters and phase shifters. Ultimately, full system tests provide a measure of merit for this work as well as invaluable lessons learned. The emphasis of this project is the on-wafer LNA measurements, dependence of IC system performance on mismatches and overall system performance tests. Where possible, predictions are plotted alongside measured data. The reasonable match between the two validates system and component models and more than compensates for the painstaking modeling efforts. Most importantly, using the signal to interferer ratio (SIR) as a figure of merit, experimental results demonstrate up to 58 dB of SIR improvement. This number represents a remarkable advancement in interference rejection at RF or microwave frequencies
Análisis y diseño de multiplicadores y mezcladores mediante el Método de Monte CArlo en la banda de THZ
[ES]La región del espectro electromagnético comprendida entre 100 GHz y 10 THz alberga una gran variedad de aplicaciones en campos tan dispares como la radioastronomÃa, espectroscopÃa molecular, medicina, seguridad, radar, etc. Los principales inconvenientes en el desarrollo de estas aplicaciones son los altos costes de producción de los sistemas trabajando a estas frecuencias, su costoso mantenimiento, gran volumen y baja fiabilidad. Entre las diferentes tecnologÃas a frecuencias de THz, la tecnologÃa de los diodos Schottky juega un importante papel debido a su madurez y a la sencillez de estos dispositivos. Además, los diodos Schottky pueden operar tanto a temperatura ambiente como a temperaturas criogénicas, con altas eficiencias cuando se usan como multiplicadores y con moderadas temperaturas de ruido en mezcladores. El principal objetivo de esta tesis doctoral es analizar los fenómenos fÃsicos responsables de las caracterÃsticas eléctricas y del ruido en los diodos Schottky, asà como analizar y diseñar circuitos multiplicadores y mezcladores en bandas milimétricas y submilimétricas.
La primera parte de la tesis presenta un análisis de los fenómenos fÃsicos que limitan el comportamiento de los diodos Schottky de GaAs y GaN y de las caracterÃsticas del espectro de ruido de estos dispositivos. Para llevar a cabo este análisis, un modelo del diodo basado en la técnica de Monte Carlo se ha considerado como referencia debido a la elevada precisión y fiabilidad de este modelo. Además, el modelo de Monte Carlo permite calcular directamente el espectro de ruido de los diodos sin necesidad de utilizar ningún modelo analÃtico o empÃrico. Se han analizado fenómenos fÃsicos como saturación de la velocidad, inercia de los portadores, dependencia de la movilidad electrónica con la longitud de la epicapa, resonancias del plasma y efectos no locales y no estacionarios. También se ha presentado un completo análisis del espectro de ruido para diodos Schottky de GaAs y GaN operando tanto en condiciones estáticas como variables con el tiempo. Los resultados obtenidos en esta parte de la tesis contribuyen a mejorar la comprensión de la respuesta eléctrica y del ruido de los diodos Schottky en condiciones de altas frecuencias y/o altos campos eléctricos. También, estos resultados han ayudado a determinar las limitaciones de modelos numéricos y analÃticos usados en el análisis de la respuesta eléctrica y del ruido electrónico en los diodos Schottky.
La segunda parte de la tesis está dedicada al análisis de multiplicadores y mezcladores mediante una herramienta de simulación de circuitos basada en la técnica de balance armónico. Diferentes modelos basados en circuitos equivalentes del dispositivo, en las ecuaciones de arrastre-difusión y en la técnica de Monte Carlo se han considerado en este análisis. El modelo de Monte Carlo acoplado a la técnica de balance armónico se ha usado como referencia para evaluar las limitaciones y el rango de validez de modelos basados en circuitos equivalentes y en las ecuaciones de arrastre-difusión para el diseño de circuitos multiplicadores y mezcladores. Una notable caracterÃstica de esta herramienta de simulación es que permite diseñar circuitos Schottky teniendo en cuenta tanto la respuesta eléctrica como el ruido generado en los dispositivos. Los resultados de las simulaciones presentados en esta parte de la tesis, tanto para multiplicadores como mezcladores, se han comparado con resultados experimentales publicados en la literatura. El simulador que integra el modelo de Monte Carlo con la técnica de balance armónico permite analizar y diseñar circuitos a frecuencias superiores a 1 THz.[EN]The terahertz region of the electromagnetic spectrum (100 GHz-10 THz) presents a wide range of
applications such as radio-astronomy, molecular spectroscopy, medicine, security and radar, among
others. The main obstacles for the development of these applications are the high production cost of
the systems working at these frequencies, high maintenance, high volume and low reliability. Among
the different THz technologies, Schottky technology plays an important rule due to its maturity
and the inherent simplicity of these devices. Besides, Schottky diodes can operate at both room
and cryogenic temperatures, with high efficiency in multipliers and moderate noise temperature in
mixers. This PhD. thesis is mainly concerned with the analysis of the physical processes responsible
for the characteristics of the electrical response and noise of Schottky diodes, as well as the analysis
and design of frequency multipliers and mixers at millimeter and submillimeter wavelengths.
The first part of the thesis deals with the analysis of the physical phenomena limiting the electrical
performance of GaAs and GaN Schottky diodes and their noise performance. To carry out this
analysis, a Monte Carlo model of the diode has been used as a reference due to the high accuracy
and reliability of this diode model at millimeter and submillimter wavelengths. Besides, the Monte
Carlo model provides a direct description of the noise spectra of the devices without the necessity
of any additional analytical or empirical model. Physical phenomena like velocity saturation, carrier
inertia, dependence of the electron mobility on the epilayer length, plasma resonance and nonlocal
effects in time and space have been analysed. Also, a complete analysis of the current noise spectra
of GaAs and GaN Schottky diodes operating under static and time varying conditions is presented
in this part of the thesis. The obtained results provide a better understanding of the electrical and the
noise responses of Schottky diodes under high frequency and/or high electric field conditions. Also
these results have helped to determine the limitations of numerical and analytical models used in the
analysis of the electrical and the noise responses of these devices.
The second part of the thesis is devoted to the analysis of frequency multipliers and mixers by
means of an in-house circuit simulation tool based on the harmonic balance technique. Different
lumped equivalent circuits, drift-diffusion and Monte Carlo models have been considered in this
analysis. The Monte Carlo model coupled to the harmonic balance technique has been used as a
reference to evaluate the limitations and range of validity of lumped equivalent circuit and driftdiffusion
models for the design of frequency multipliers and mixers. A remarkable feature of this
reference simulation tool is that it enables the design of Schottky circuits from both electrical and
noise considerations. The simulation results presented in this part of the thesis for both multipliers
and mixers have been compared with measured results available in the literature. In addition, the
Monte Carlo simulation tool allows the analysis and design of circuits above 1 THz
System data communication structures for active-control transport aircraft, volume 2
The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems
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