In the past decade we have seen fast development of new quantum technologies that promise to revolutionise communications and computing. Many different routes are explored to physically implement such quantum technologies. Among others, we can mention superconducting circuits, spin-based devices and photonic devices.  An active area of research concerns hybrid quantum systems, which aim at combining the best properties of these different implementations. Recently quantum acoustics has been gaining interest as a potential intermediate in such hybrid systems. Indeed, phonons can couple to many different degrees of freedom and could therefore form an interface between different quantum systems.One method to convert microwaves to an acoustic signal relies on the exploitation of the piezoelectric effect. However, for transducer devices based on the piezoelectric effect, the operating bandwidth has remained limited. By using tunable matching circuits, we propose a device capable of performing piezoelectric transduction over large bandwidths. The tunability is achieved by using SQUID transmission lines. This work reports some preliminary studies towards the creation of such a platform. We conduct measurements at cryogenic temperatures on suspended lithium niobate delay lines. These allow us to characterise the dependence of the IDT response on various parameters such as the number of fingers and the angle relative to the underlying crystal. We show that certain angles favour transduction into a single acoustic mode. In parallel, we characterise transmission lines consisting of one-dimensional arrays of SQUIDs. By applying magnetic flux to these lines, we show that it is possible to tune their impedance. These experiments improved our understanding of both IDTs and SQUID transmission lines and pave the way for the implementation of our experimental platform. / Under det senaste decenniet har vi sett en snabb utveckling av ny kvantteknologi som kommer att revolutionera telekommunikation och databehandling. Många olika vägar utforskas för att fysiskt realisera sådan kvantteknologi. Bland annat kan vi nämna supraledande kretsar, spinbaserade anordningar och fotoniska anordningar.  Ett aktivt forskningsområde är hybrida kvantsystem som kombinera de bästa egenskaperna hos dessa olika tillämpningar. På senare tid har kvantakustik fått ökat intresse som en potentiell mellansteg i sådana hybridsystem. Fononer kan kopplas till många olika frihetsgrader och skulle därför kunna fungera som ett gränssnitt mellan olika kvantsystem.En metod för att omvandla mikrovågor till en akustisk signal bygger på utnyttjandet av den piezoelektriska effekten. För transduceranordningar som bygger på den piezoelektriska effekten har dock den operativa bandbredden fortfarande varit liten. Genom att använda avstämbara anpassningskretsar föreslår vi en anordning som kan utföra piezoelektrisk transduktion över stora bandbredder. Avstämbarheten uppnås med hjälp av SQUID-överföringsledningar. I detta arbete rapporteras några preliminära studier för att skapa en sådan plattform. Vi utför mätningar vid kryogena temperaturer på upphängda fördröjningsledningar av litiumniobat. Dessa gör det möjligt för oss att karakterisera IDT-svarets beroende av olika parametrar, t.ex. antalet fingrar och vinkeln i förhållande till den underliggande kristallen. Vi har visat att vissa vinklar gynnar transduktion till ett enda akustiskt läge. Parallellt karakteriserar vi transmissionsledningar som består av endimensionella matriser av SQUIDs. Genom att applicera magnetiskt flöde på dessa linjer visar vi att det är möjligt att ställa in deras impedans. Dessa experiment förbättrade vår förståelse av både IDT:er och SQUID-överföringslinjer och banar väg för genomförandet av vår experimentella plattform.

No description available.

The proposed circuit intends to harvest kinetic energy from ElectroMagnetic Generators (EMGs). In order to extract maximum power from an EMG, an AC-DC boost rectifier is designed to match the impedance of the EMG. Rather than operate a buck-boost converter in Discontinuous Conduction Mode (DCM) in other impedance matching cases, the proposed method is running the boost topology in Boundary Conduction Mode (BCM). So it would perform resistive input matching, while reducing the converter power loss. The boost rectifier also merges a rectifier and a boost converter to reduce power loss for rectification. It also utilizes the internal inductance of the EMG to eliminate the impedance matching error and reduce the off-chip inductor size. An optional buck converter regulates the output voltage to 5 V to power devices through USB ports. The proposed circuit is designed and fabricated in BiCMOS 0.18 μm technology. Its functionality is shown through simulation results. The measurement of the IC is also performed. However, since the IC only work partially, test result is gathered using some discrete components as substitutes. It indicates the circuit can realize the proposed control method. / Master of Science / The development of energy-efficient semiconductor devices has reduced the power requirements of electronic circuits. As the electronics’ scale decreases, so does the energy consumption. In this sense, batteries were also produced in smaller size providing more energy storage availability. However, due to technical and technological issues, the batteries have not been followed by the same evolutionary trend limiting the operational time and performance of portable devices as it need to be recharged or replaced periodically. On the other hand, portable electronic devices such as cell phones, GPS, cameras, etc. are powered only by batteries. For circumstances that power supplies are not accessible, energy harvesting (EH) from human or environmental sources has proven to be an effective alternative or complement. Light, thermal, mechanical and RF are major sources in EH. Among them, mechanical energy from wind, waves, vibrations, etc. is commonly existed in our daily life. The energy is harvested by using micro generators and the various types include electromagnetic, piezoelectric and electrostatic. In particular, the ElectroMagnetic Generator (EMG) is of great interest for its potentially high energy density and efficiency. Since EMG is an AC voltage generator while portable devices usually require a stable DC supply, an EH circuit as a rectifier ought to be designed. At the same time, for EH application, we would like to harvest as much power as possible from EMGs. This research project addresses the development of a unique EH circuit capable of fulfilling the distinct needs illustrated above.

Yes / Matching the antenna’s impedance to the RF-front-end of a wireless communications system is challenging as the impedance varies with its surround environment. Autonomously matching the antenna to the RF-front-end is therefore essential to optimize power transfer and thereby maintain the antenna’s radiation efficiency. This paper presents a theoretical technique for automatically tuning an LC impedance matching network that compensates antenna mismatch presented to the RF-front-end. The proposed technique converges to a matching point without the need of complex mathematical modelling of the system comprising of non-linear control elements. Digital circuitry is used to implement the required matching circuit. Reliable convergence is achieved within the tuning range of the LC-network using control-loops that can independently control the LC impedance. An algorithm based on the proposed technique was used to verify its effectiveness with various antenna loads. Mismatch error of the technique is less than 0.2%. The technique enables speedy convergence (< 5 µs) and is highly accurate for autonomous adaptive antenna matching networks. / This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE), and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

Les étiquettes d'identification radiofréquence passifs (RFID) sont des systèmes télé-communiquant dont l'approvisionnement en énergie se fait via les ondes électromagnétiques. De plus en plus présents dans notre environnement (passeport, badge d'accès, gestion de stock), ils ont l'avantage d'avoir une durée de vie presque infinie, et ne consomment de l'énergie que lorsqu'ils sont sollicités. Par ailleurs, leur moyen de communiquer, sans fil, permet de les utiliser dans des endroits difficiles d'accès pour des lecteurs optiques type code à barre. Toutefois, la portée de tels systèmes est limitée par l'efficacité de la récupération de l'énergie provenant des ondes. Dans ce cadre, l'augmentation de la portée des étiquettes RFID, notamment pour les applications de logistique est un élément primordial.Sont présentés dans cette thèse différents moyens d'augmenter cette portée notamment grâce à l'amélioration des blocs de récupération d'énergie ou l'adaptation d'impédance, tout en respectant des contraintes liées au coût du système. La première partie se focalise sur la réduction des pertes du bloc de récupération d'énergie par l'optimisation du layout. Une architecture à haut rendement à transistor polarisé est ensuite proposée. Pour finir, l'impact de la rétro-modulation et de l'adaptation d'impédance en fréquence sur la récupération d'énergie sont étudiés et améliorés. / The passive radio frequency identification tags (RFID) systems communicate with a remote power supply thanks to electromagnetic waves. Increasingly present in our environment (biometric passport, inventory management), they present the advantage to have an almost infinite lifetime, and consume energy only when they are solicited. Moreover, because it is a wireless way to communicate, it is possible to use these systems places inaccessible to optical drives type bar code. However, the range of such systems is limited by the efficiency of the recovery of energy from waves. In this context, increasing the range of RFID tags, especially for logistics applications is essential.In this these, different ways to increase the range are studied. The first part focuses on the reduction of losses on the rectifying circuitry thanks to layout optimization. An high performances architecture with transistor biased is then proposed. Finally, the impact of backscattering and impedance matching on the energy recovery are studied and improved.

Le contexte de la thèse se situe sur le marché du NFC, des cartes sécurisées ainsi que du paiement sans contact qui sont en forte croissance ces dernières années. L’objectif est de développer un environnement de simulation afin de concevoir différents dispositifs NFC destinés à des produits nomades comme un smartphone ou une tablette tactile et qui répondent aux différentes normes NFC. / The thesis context is focused on the NFC market, secure cards and contactless paiement which are in strong development in recent years. The objective is to develop a simulation environment to design NFC features for mobile devices as smartphone or tactile tablet which satisfy NFC standards.

With  the  continuous  advances  in  microwave  technology,  microwave  components  and  related magnetic materials become more important in industrial environment. In order to further develop the microwave components, it is of interest to find new kinds of technologies and materials. Here, we  introduce  a  new  kind  of  material  --  amorphous  metallic  wires  which  could  be  used  in microwave  components,  and  use  these  wires  to  design  new  kinds  of  attenuators.  Based  on  the fundamental  magnetic  properties  of  amorphous  wires  and  transmission  line  theory,  we  design  a series of experiments focusing on these wires, and analyze all the experimental results.    Experimental  results  show  that  incident  and  reflected  signals  produce  interference  and  generate standing  waves  along  the  wire.  At  given  frequency,  the  insertion  attenuation  S21 [dB]  of  an amorphous wire increases monotonically with dc bias current. The glass cover will influence the  magnetic  domain  structure  in  amorphous  metallic  wires.  Therefore,  it  will  affect  the circumference  permeability  and  change  the  signal  attenuation.  It  is  necessary  to  achieve  the impedance  matching  by  coupling  to  an  inductor  and  a  capacitor  in  the  circuit.  The  impedance matching  makes  the  load  impedance  close  to  the  characteristic  impedance  of  transmission  line. The magnetic wire-based attenuator designed in this thesis work are characterized and compared to conventional pin-diode attenuator.

When multiple cold cathode fluorescent lamps (CCFLs) are set up in a backlight module, parasitic capacitances are inevitably existent between the lamps and the aluminum back-plank. These parasitic capacitances are different from each other in introducing different leakage currents, and in turn cause current imbalance between lamps with undesired unequal brightness of the backlight module. In order to tackle this current imbalance problem, it relies critically upon a balance driving scheme. This thesis adopts the impedance-matching principle for a uniform light output. A detailed analysis and design of the balance circuit is implemented in a direct-type backlight module, which employs a series resonant parallel-loaded inverter with a transformer to generate a high AC voltage to drive multiple lamps. Adding appropriate capacitors on the load resonant circuits helps alleviate the discrepancy among lamp currents. Based on the experimental results, the maximum total current deviation is defined as an index of the current imbalance for multiple lamps system. Accordingly, the minimum impedance ratio can be provided for the designers to achieve balance driving. A prototype of the multi-lamp driving circuit with balance capacitors is designed and built for a backlight module with 16 lamps in a 32-inch liquid crystal display (LCD). Simulation and experimental results demonstrate the effectiveness and feasibility of the current balance scheme.

The use of full wave electromagnetic modeling and simulation tools allows for accurate performance predictions of unique RF structures that exhibit multi-dimensional scales. Full wave simulation tools need to cover the broad range of frequency including RF and terahertz bands that is focused as RF technology is developed. In this dissertation, three structures with multi-dimensional scales and different operating frequency ranges are modeled and simulated. The first structure involves nanostructured solar cells. The silicon solar cell design is interesting research to cover terahertz frequency range in terms of the economic and environmental aspects. Two unique solar cell surfaces, nanowire and branched nanowire are modeled and simulated. The surface of nanowire is modeled with two full wave simulators and the results are well-matched to the reference results. This dissertation compares and contrasts the simulators and their suitability for extensive simulation studies. Nanostructured Si cells have large and small dimensional scales and the material characteristics of Si change rapidly over the solar spectrum. The second structure is a reconfigurable four element antenna array antenna operating at 60 GHz for wireless communications between computing cores in high performance computing systems. The array is reconfigurable, provides improved transmission gain between cores, and can be used to create a more failure resilient computing system. The on-chip antenna array involves modeling the design of a specially designed ground plane that acts as an artificial magnetic conductor. The work involves modeling antennas in a complex computing environment. The third structure is a unique collar integrated zig-zag antenna that operates at 154.5 MHz for use as a ground link in a GPS based location system for wildlife tracking. In this problem, an intricate antenna is modeled in the proximity of an animal. Besides placing a low frequency antenna in a constricted area (the collar), the antenna performance near the large animal body must also be considered. Each of these applications requires special modeling details to take into account the various dimensional scales of the structures and interaction with complex media. An analysis of the challenges and limits of each specific problem will be presented.

In this thesis we introduce a two-way Doherty amplifier architecture with multiple feedbacks for digital predistortion based on impedance-inverting directional coupler (transcoupler). The tunable two-way Doherty amplifier with a tuned circulator-based impedance inverter is presented. Compact N-way Doherty architectures that subsume impedance inverter and offset line functionality into output matching networks are derived. Comprehensive N-way Doherty amplifier design and analysis techniques based on load-pull characterization of active devices and impedance modulation effects are developed. These techniques were then applied to the design of a two-way Doherty amplifier and a three-way Doherty amplifier which were manufactured and their performance measured and compared to the amplifier performance specifications and simulated results.