Frequency Independent Framework for Synthesis of Programmable Non-reciprocal Networks

Passive and linear nonreciprocal networks at microwave frequencies hold great promises in enabling new front-end architectures for wireless communication systems. Their nonreciprocity has been achieved by disrupting the time-reversal symmetry using various forms of biasing schemes, but only over a limited frequency range. Here we demonstrate a framework for synthesizing theoretically frequency-independent multi-port nonreciprocal networks. The framework is highly expandable, and can have an arbitrary number of ports while simultaneously sustaining balanced performance and providing unprecedented programmability of non-reciprocity. A 4-port circulator based on such a framework is implemented and tested to produce broadband nonreciprocal performance from 10 MHz to 900 MHz with a temporal switching effort at 23.8 MHz. With the combination of broad bandwidth, low temporal effort, and high programmability, the framework could inspire new ways of implementing multiple input multiple output (MIMO) communication systems for 5G.Comment: 10 pages, 6 figure

Measurements, Models, Systems and Design

531 s.

Broad-band microwave amplifier design considerations

Broad-band microwave integrated circuit (MIC) amplifier design is a complex, multi-disciplinary process. This work focuses on three important aspects: the behaviour of microstrip transmission lines, discontinuities, and related structures; the accurate measurement of components and devices mounted in microstrip circuits; and the circuit design methodology. Techniques for microstrip quasi-static analysis are reviewed in order to identify methods suitable for extension to deal with the effects of substrate anisotropy. An integral equation method is described and the anisotropic Green's function derived using an extension to the method of partial images. Proposed transform methods are assessed and the preferred option implemented by adaption of a microstrip analysis computer program. A method, by which accurate measurements of microstrip properties may be made, is developed. Involving measurements of the resonant behaviour of half-wavelength short circuit resonators with two arbitrary coupling conditions, this technique allows the unloaded properties to be deduced. Results for microstrip on a sapphire substrate concur with the analysis. A pragmatic but effective approach to the calculation of the capacity component of microstrip discontinuities, and some other three dimensional MIC structures, is described and developed to allow existing data for isotropic substrates to be applied to the anisotropic situation. The computer corrected network analyser (CCNA) is a widely used microwave measurement tool. Weaknesses in popular correction strategies are identified and remedies developed. In particular, revised calibration equations that better accommodate test port mismatch variation with s-parameter selection, and a model for quadrature error are presented. A 2-port calibration scheme suitable for use with MIC transmission lines, using only simple standards, is described. The standards are partially self-calibrating;the values of propagation constant, loss, and end effect are deduced in the calibration process. An effective jig for use with microstrip is described and the results of measurements on microwave transistors presented. Conventionally microwave amplifiers are designed using reactive components both to achieve good port matches and compensate the frequency dependent gain of the active devices. The problems associated with this approach are enumerated and the alternatives reviewed. A methodology which combines the benefits of frequency dependant dissipative networks with the elegance of reactive network synthesis is described. The device gain slope is compensated by simple lumped or distributed circuits incorporating a resistive element to produce a composite `device' with a specififed (flat) maximum available gain frequency response. Reactive matching networks are then used to interface these gain blocks. By this structured approach the amplifier gain breakdown can be defined at the outset and preserved through the design process. Other advantages stemming from the use of dissipative compensation include improved tolerance to device parameter and component value scatter, reduced group delay variations and enhanced reverse isolation. The method is demonstrated by the design and characterisation of 4 to 9 GHz amplifier having a representative specification. The close conformance of the performance of the untrimmed amplifier to that predicted by computer simulation testifies to the inherent accuracy of the design method, the microstrip (and related structures) analysis techniques and the CCNA MIC calibration scheme

Communication systems using visible light : emitter/receiver

Mestrado em Engenharia Electrónica e TelecomunicaçõesA presente dissertação aborda o design de um transdutor optoelectrónico para um sistema de comunicações sem fios que utiliza a luz visível como meio de transmissão. Estes sistemas tiram partido dos conhecimentos tecnológicos existentes sobre sistemas de comunicações sem fios utilizando o espectro dos infravermelhos, e da recente introdução em massa de díodos emissores de luz de elevado brilho em diversas aplicações de iluminação. O trabalho apresentado foi desenvolvido dentro do projecto VIDAS, tendo em conta os respectivos cenários de aplicação propostos. Este projecto visa aumentar a segurança rodoviária através da introdução de sistemas de comunicação com luz visível, para estabelecer ligações veículo-a-veículo e/ou veículo-a-semáforo. Através destas ligações, poderão ser antecipadamente fornecidos diversos avisos de segurança aos condutores. O estudo do transdutor proposto, começa com uma introdução ao conceito e evolução dos sistemas de comunicação com luz visível. Segue-se uma apresentação do canal de transmissão, na qual são definidos os modelos de emissor, receptor e propagação. São também discutidas as diversas fontes de ruído óptico e suas influências na aplicação pretendida. A restante análise é dividida em dois dispositivos principais, o emissor e o receptor ópticos. Sobre o emissor, são apresentados os principais blocos funcionais, seguidos de uma exposição das características de diversos díodos emissores de luz e da análise de diferentes topologias de receptor. Para a topologia mais viável de ser implementada, são apresentados diversos resultados de simulação do circuito electrónico. Do lado do receptor, de forma análoga, são apresentados os diferentes blocos funcionais e as características de diversos fotodíodos. No entanto a experiência do grupo de trabalho levou à escolha de uma topologia de receptor mais específica. Desta, fazem parte diversos módulos, cuja análise e resultados de simulação dos respectivos circuitos electrónicos são apresentados. De forma a avaliar a performance dos dispositivos propostos, foram efectuados diversos ensaios e respectivas medições. Estes resultados permitiram obter informações sobre o comportamento da componente óptica do sistema. Deste conjunto de informações, diferentes considerações sobre a performance de módulos individuais e do transdutor são apresentadas. Estas permitem concluir sobre a viabilidade do transdutor optoelectrónico num cenário de aplicação real. ABSTRACT: This dissertation addresses the design of an optoelectronic transceiver for a wireless communication system, using visible light as the transmission medium. These systems take advantage from the available technological expertise on wireless communication systems using the infrared spectrum, along with the recent massive introduction of high brightness light emitting diodes in several lighting applications. The present work was developed within the scope of project VIDAS, regarding the proposed application scenarios. This project aims at increasing road traffic safety by introducing visible light communication systems to establish vehicle-to-vehicle and vehicle-to-traffic light communications. Through these connections, early safety warnings can be provided to drivers. The study of the proposed transceiver begins with an introduction to the concept and evolution of visible light communication systems. This is followed by the presentation of the transmission channel, in which the emitter, receiver and transmission models are defined. Also, the sources and influences of the various optical noise sources are discussed. The remaining analysis is divided between the two major devices, the optical emitter and receiver. From the emitter, the main building blocks are presented, followed by an exposition of several light emitting diodes characteristics and the analysis of diverse receiver topologies. In the case of the most viable topology for implementation, several simulation results of the respective electronic circuit are presented. On the receiver, the main building blocks and the characteristics of several photodiodes are presented in a similar fashion. However, the workgroup experience led to the choice of a specific receiver topology. This is made up of several modules, whose analysis and simulation results for the electronic circuits are presented. In order to evaluate the performance of the proposed devices, several tests and measurements were made. These results also provided information on the system’s optical component behavior. From this assortment of information, different considerations on the performance of the individual modules, as well as the transceiver are presented. They allow for a conclusion on the viability of the optoelectronic transceiver in a real application scenar

Power Quality in Electrified Transportation Systems

"Power Quality in Electrified Transportation Systems" has covered interesting horizontal topics over diversified transportation technologies, ranging from railways to electric vehicles and ships. Although the attention is chiefly focused on typical railway issues such as harmonics, resonances and reactive power flow compensation, the integration of electric vehicles plays a significant role. The book is completed by some additional significant contributions, focusing on the interpretation of Power Quality phenomena propagation in railways using the fundamentals of electromagnetic theory and on electric ships in the light of the latest standardization efforts

Millimeter-Wave Super-Regenerative Receivers for Wireless Communication and Radar

Today’s world is becoming increasingly automated and interconnected with billions of smart devices coming online, leading to a steep rise in energy consumption from small microelectronics. This coincides with an urgent push to transform global energy production to green energies, causing disruptions and energy shortages, and making the case for efficient energy use ever more pressing. Two major areas where high growth is expected are the fields of wireless communication and radar sensors. Millimeter-wave frequency bands are planned for fifth-generation (5G) and sixth-generation (6G) cellular communication standards, as well as automotive frequency-modulated continuous wave (FMCW) radar systems for driving assistance and automation. Fast silicon-based technologies enable these advances by operating at high maximum frequencies, such as the silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies. However, even the fastest transistors suffer from low and energy expensive gains at millimeter-wave frequencies. Rather than incremental improvements in circuit efficiency using conventional approaches, a disruptive revolution for green microelectronics could be enabled by exploring the low-power benefits of the super-regenerative receiver for some applications. The super-regenerative receiver uses a regenerative oscillator circuit to increase the gain by positive feedback, through coupling energy from the output back into the input. Careful bias and control of the circuit enables a very large gain from a small number of transistors and a very low energy dissipation. Thus, the super-regenerative oscillator could be used to replace amplifier circuits in high data rate wireless communication systems, or as active reflectors to increase the range of FMCW radar systems, greatly reducing the power consumption. The work in this thesis presents fundamental scientific research into the topic of energy-efficient millimeter-wave super-regenerative receivers for use in civilian wireless communication and radar applications. This research work covers the theory, analysis, and simulations, all the way up to the proof of concept, hardware realization, and experimental characterization. Analysis and modeling of regenerative oscillator circuits is presented and used to improve the understanding of the circuit operation, as well as design goals according to the specific application needs. Integrated circuits are investigated and characterized as a proof of concept for a high data rate wireless communication system operating between 140–220 GHz, and an automotive radar system operating at 60 GHz. Amplitude and phase regeneration capabilities for complex modulation are investigated, and principles for spectrum characterization are derived. The circuits are designed and fabricated in a 130 nm SiGe HBT technology, combining bipolar and complementary metal-oxide semiconductor (BiCMOS) transistors. To prove the feasibility of the research concepts, the work achieves a wireless communication link at 16 Gbit/s over 20 cm distance with quadrature amplitude modulation (QAM), which is a world record for the highest data rate ever reported in super-regenerative circuits. This was powered by a super-regenerative oscillator circuit operating at 180 GHz and providing 58 dB of gain. Energy efficiency is also considerably high, drawing 8.8 mW of dc power consumption, which corresponds to a highly efficient 0.6 pJ/bit. Packaging and module integration innovations were implemented for the system experiments, and additional broadband circuits were investigated to generate custom quench waveforms to further enhance the data rate. For radar active reflectors, a regenerative gain of 80 dB is achieved at 60 GHz from a single circuit, which is the best in its frequency range, despite a low dc power consumption of 25 mW

Flexor Dysfunction Following Unilateral Transient Ischemic Brain Injury Is Associated with Impaired Locomotor Rhythmicity

Functional motor deficits in hemiplegia after stroke are predominately associated with flexor muscle impairments in animal models of ischemic brain injury, as well as in clinical findings. Rehabilitative interventions often employ various means of retraining a maladapted central pattern generator for locomotion. Yet, holistic modeling of the central pattern generator, as well as applications of such studies, are currently scarce. Most modeling studies rely on cellular neural models of the intrinsic spinal connectivity governing ipsilateral flexor-extensor, as well as contralateral coupling inherent in the spinal cord. Models that attempt to capture the general behavior of motor neuronal populations, as well as the different modes of driving their oscillatory function in vivo is lacking in contemporary literature. This study aims at generating a holistic model of flexor and extensor function as a whole, and seeks to evaluate the parametric coupling of ipsilateral and contralateral half-center coupling through the means of generating an ordinary differential equation representative of asymmetric central pattern generator models of varying coupling architectures. The results of this study suggest that the mathematical predictions of the locomotor centers which drive the dorsiflexion phase of locomotion are correlated with the denervation-type atrophy response of hemiparetic dorsiflexor muscles, as well as their spatiotemporal activity dysfunction during in vivo locomotion on a novel precise foot placement task. Moreover, the hemiplegic solutions were found to lie in proximity to an alternative task-space solution, by which a hemiplegic strategy could be readapted in order to produce healthy output. The results revealed that there are multiple strategies of retraining hemiplegic solutions of the CPG. This solution may modify the hemiparetic locomotor pattern into a healthy output by manipulating inter-integrator couplings which are not damaged by damage to the descending drives. Ultimately, some modeling experiments will demonstrate that the increased reliance on intrinsic connectivity increases the stability of the output, rendering it resistant to perturbations originating from extrinsic inputs to the pattern generating center