Millimetre-wave nonreciprocal devices are vital elements in many modern radar and communication systems. Gyromagnetic behaviour in magnetised ferrite materials has been utilised for decades in the design of nonreciprocal devices. However, the effects of ferrite's limited saturation magnetisation and high loss as the frequency of operation exceeds 40 GHz render such devices inadequate for millimetre-wave applications. On the other hand, solid plasma (such as semiconductors) are known to exhibit gyrotropic behaviour when they are biased with a steady magnetic field. This behaviour (which is referred to as gyroelectric) can extend up to the THz frequency ranges. Hence, magnetised semiconductors can be regarded as suitable candidates for realising millimetre-wave, sub-millimetre-wave and even THz nonreciprocal devices. This thesis focuses on analysing different structures containing gyroelectric materials, and proposing millimetre-wave nonreciprocal devices based on the theoretical findings. Measurements and full wave electromagnetic simulation are used to validate and optimise the proposed designs where possible. Before starting the electromagnetic analysis, the physical properties of a semiconductor plasma are studied, then a permittivity tensor is introduced to include the microscopic features of the magnetised semiconductors into a macroscopic model. Different semiconductor candidates for gyroelectric designs are also discussed and analysed. Firstly, Semiconductor Junction Circulators (SJC's) are analysed using a Green's function approach. The same approach is then used to proposed new designs for broadband millimetre-wave SJC's that require low magnetic bias using Indium Antimonide (InSb) cooled down to 77 K. The possibility of realising planar nonreciprocal devices using a Molecular Beam Epitaxy (MBE) grown Two Dimensional Electron Gas (2-DEG) is also studied. Theoretical and simulation results prove the possibility of using this material to realise millimetre-wave resonators and circulators. Then a novel type of circulator is realised by placing an InSb disk at 77 K in the middle of a three port waveguide junction. The structure is analysed by treating the junction as a resonator with a suspended axially magnetised gyroelectric rod placed in the middle. Electromagnetic analysis, simulations and measurements reveal the existence of counter rotating modes that degenerate or split at certain frequencies under specific magnetic bias conditions. Measuring this circulator reveals an isolation of 18 dB at 38.5 GHz when the InSb disk is biased with a D.C. magnetic flux of 0.55 T. This is the first time such a circulator has been demonstrated theoretically and experimentally. In addition to the three port circulator, a model is developed for a rectangular waveguide loaded with layered dielectric and gyroelectric media. Mathematical analysis reveals the dispersion relations and field distributions for such a structure. High nonreciprocity in both phase and attenuation constants is observed from analysing a rectangular waveguide loaded with a transversely biased InSb slab at 77 K. The expected nonreciprocity is then verified, for the first time, by simulation and measurement of similar structures under the same conditions. More than 35 dB of isolation at f=35.6 GHz was obtained when loading a WR-28 rectangular waveguide with an InSb slab at 77 K, transversely biased with a magnetic flux of 0.8 T. Different effects on the isolation behaviour are also discussed theoretically and experimentally, including the effects of the slab's thickness and length, the magnetic bias and the existence of a dielectric layer above the gyroelectric slab. Theoretical and experimental outcomes of this thesis prove the possibility of using gyroelectric materials to develop a new class of component that meets the demands for millimetre-wave nonreciprocal devices. This will provide a significant improvement to the modern high frequency millimetre-wave systems.

Seismic base isolation has become an increasingly common approach to reduce earthquake induced losses. Base isolation aims to decouple structures, such as buildings or bridges, from strong ground motions through the introduction of a flexible layer, typically located at the foundation. Base isolation is a well-established concept and accepted as an effective method of protecting both the structure and its contents from damage due to earthquakes. Elastomers are ideal for base isolation due to their soft material properties and ability to undergo large recoverable strains. Steel-reinforced elastomeric isolators (SREIs) have been widely applied as base isolators; however, the weight and cost of SREIs have been perceived as barriers to the widespread application of base isolation. In order to alleviate these concerns, it has been proposed that the steel reinforcement could be replaced with lighter fiber reinforcement with similar tensile properties as steel. Recent investigations have demonstrated that fiber-reinforced elastomeric isolators (FREIs) are viable and have desirable characteristics. An additional proposed cost saving measure was to place the FREI unbonded between the upper and lower supports. The combination of the flexible fiber reinforcement and the unbonded application resulted in a unique rollover deformation under horizontal displacement. Rollover causes a nonlinear force-displacement relationship characterized by a softening and stiffening phase. This nonlinear relationship is believed to be advantageous and to allow the performance of the device to be tailored to the earthquake hazard level. This work investigates the adaptive characteristics of unbonded FREIs. It is demonstrated that the softening and stiffening characteristics of the isolator can be altered through modifications to the isolator or to the surrounding support geometry. Equations are developed to predict the horizontal force-displacement relationship. Furthermore, simple expressions appropriate for use in building and bridge design codes are proposed for critical isolator properties. Potential limitations introduced due to the unbonded application are identified and addressed through the development of a new partially bonded hybrid isolator. It is demonstrated that unbonded FREIs are highly versatile and a potentially competitive device appropriate for widespread application in developed and developing countries. / Thesis / Doctor of Philosophy (PhD) / Earthquakes remain a significant and potentially devastating threat to both developed and developing countries. Structural elements within a building, such as beams and columns, must deform considerably to accommodate the relative floor displacements that develop due to ground motion. Conventional construction materials are not capable of undergoing these large deformations without irreversible and potentially catastrophic damage. The introduction of a flexible layer at the foundation level of a structure, using elements known as isolators, can dramatically reduce damage. The deformation is concentrated at the flexible layer, which can undergo large displacements without any damage. This concept, known as base isolation, protects both the structure and its contents. Traditional isolators are expensive, thus far hindering the application of base isolation systems. A novel isolator design has been proposed that has the potential for widespread economical application. To increase the application, building codes need to be developed, requiring substantial research on the isolator properties. A key component of the novel isolator is the ability to alter the isolator geometry to further enhance the response. This is validated through experimental testing and complex computer models.

No description available.

Commutated N-path networks have seen a resurgence in the past decade in the context of modern integrated circuits. N-path circuits have been used to implement high-quality tunable band-pass and notch filters with just switches and capacitors. Recently, nonreciprocal circuits such as circulators and isolators have also been reported as other applications of Linear Periodically-Time-Varying (LPTV) networks. In this dissertation, high performance filters and inductorless nonreciprocal components based on novel LPTV networks are introduced. We proposed a concept called Negative Transresistance (NTR) in phase-shifted N-path structures. The rejection of the conventional N-path notch filters is limited to the number of paths used; however, by using our proposed NTR concept, we were able to achieve more than 50dB rejection regardless of the number of paths. Using the same concept, we introduced the first prototype of N-path Low-Pass Filter (LPF). The resulting components can find application in blocker-tolerant systems, to select closely-spaced frequency channels, and also in the analog Baseband (BB). Nonreciprocal components such as circulators and isolators have traditionally relied on ferrites that offer nonreciprocal behavior based on Faraday Effect (by applying an external magnetic field). Recent efforts to eliminate the need for magnetic materials, despite being a huge success involve the usage of transmission lines (and/or inductors). In this dissertation, a novel concept called Nonreciprocal Transresistance (NRTR) is introduced. This led to the first ever inductorless RF isolator. Furthermore, we expanded the idea to the first inductorless circulator consisting of only switches and capacitors. The resulting isolator can find application in base stations to prevent back reflections (e.g. to protect the Power Amplifier (PA)). Also, in superconducting quantum systems, an isolator is necessary to separate the noise and reflections at the interface of different blocks. The introduced circulator can find applications in wireless communication systems as an antenna interface connecting the Transmitter (TX) and the Receiver (RX) to a shared antenna. This is crucial, especially for Full-Duplex (FD) applications where high isolation between RX and TX is necessary as they are operating at the same frequency. Finally, we enhanced the performance of the conventional N-path Band-Pass Filter (BPF). We first introduced a second-order N-path BPF with passive gain called impedance-transforming N-path filter. We then proposed a concept called rotary-clock-path in N-path filters which enables passive frequency shifting of N-path filters of any kind without the need for a separate clock frequency or active circuitries. Then by combining the impedance-transforming BPF and rotary-clock-path ideas, we implemented the first ever inductorless passive higher-order N-path BPF with voltage gain. The resulting BPFs can find applications in matching networks and also in a Surface Acoustic Wave (SAW)-less mixer-first receivers.

No description available.

This Thesis is devoted to the study of topological phases of matter in optical platforms, focusing on non-Hermitian systems with gain and losses involving nonreciprocal elements, and fractional quantum Hall liquids where strong interactions play a central role.In the first part we investigated nonlinear Taiji micro-ring resonators in passive and active silicon photonics setups. Such resonators establish a unidirectional coupling between the two whispering-gallery modes circulating in their perimeter. We started by demonstrating that a single nonlinear Taiji resonator coupled to a bus waveguide breaks Lorentz reciprocity. When a saturable gain is added to a single Taiji resonator, a sufficiently strong unidirectional coupling rules out the possibility of lasing in one of the whispering-gallery modes with independence of the type of optical nonlinearity and gain saturation displayed by the material. This can be regarded as a dynamical time-reversal symmetry breaking. This effect is further enhanced by an optical Kerr nonlinearity. We showed that both ring and Taiji resonators can work as optical isolators over a broad frequency band in realistic operating conditions. Our proposal relies on the presence of a strong pump in a single direction: as a consequence four-wave mixing can only couple the pump with small intensity signals propagating in the same direction. The resulting nonreciprocal devices circumvent the restrictions imposed by dynamic reciprocity. We then studied two-dimensional arrays of ring and Taiji resonators realizing quantum spin-Hall topological insulator lasers. The strong unidirectional coupling present in Taiji resonator lattices promotes lasing with a well-defined chirality while considerably improving the slope efficiency and reducing the lasing threshold. Finally, we demonstrated that lasing in a single helical mode can be obtained in quantum spin-Hall lasers of Taiji resonators by exploiting the optical nonlinearity of the material. In the second part of this Thesis we dived into more speculative waters and explored fractional quantum Hall liquids of cold atoms and photons. We proposed strategies to experimentally access the fractional charge and anyonic statistics of the quasihole excitations arising in the bulk of such systems. Heavy impurities introduced inside a fractional quantum Hall droplet will bind quasiholes, forming composite objects that we label as anyonic molecules. Restricting ourselves to molecules formed by one quasihole and a single impurity, we find that the bound quasihole gives a finite contribution to the impurity mass, that we are able to ascertain by considering the first-order correction to the Born-Oppenheimer approximation. The effective charge and statistical parameter of the molecule are given by the sum of those of the impurity and the quasihole, respectively. While the mass and charge of such objects can be directly assessed by imaging the cyclotron orbit described by a single molecule, the anyonic statistics manifest as a rigid shift of the interference fringes in the differential scattering cross section describing a collision between two molecules.

Spacecrafts are generally equipped with high precision optical and other sensor payloads. The structures of most of the spacecrafts are light-weight, flexible and have low damping. Vibrations are often induced in the spacecraft body due to the presence of many disturbance sources such as momentum/reaction wheels, control thrusters used for attitude control and cryocoolers etc. Low damping leads to long decay time for vibrations hence during this period the spacecraft sensors cannot be used effectively. One possible solution is to isolate the precision sensor from the rest of the satellite and this strategy has been used for spaceborne telescopes and interferometers that have extremely precise positional and vibratory tolerances imposed on them in order to achieve scientific goals. Another strategy is to isolate the vibration source itself from the spacecraft body. This thesis deals with modelling, analysis and experimentation of a novel low frequency flexible space platform designed to serve as a mount for the disturbance source in order to insulate the source generated vibrations reaching critical areas of the structure. The novel space platform consisting of folded continuous beams, is light-weight and is capable of isolating vibration generated by sources such as reaction/momentum wheels. Finite element analysis of the platform is carried out for static and dynamic load cases. Simulation studies are carried out on flexible beam platform in order to firm up the design for passive vibration isolation. Modal analyses is done to simulate the response of each mode. Active control has been studied by embedding the platform’s beam elements with piezo actuators and sensors. The simulation results show that the space platform can effectively attenuate vibration and further improvement in vibration attenuation is possible with active control. Based on the analysis, a prototype low frequency platform has been designed and fabricated. An experimental validation has been done to test the usefulness of the low frequency platform to act as a mount for reaction wheels and to mitigate the vibration disturbances/effects transmitted from the reaction wheel assembly to structure. Measurements and tests have been conducted at varying wheel speeds to quantify and characterize the amount of isolation to the reaction wheel generated vibrations. The time and frequency domain analysis of test data clearly show that level of isolation is significant and an average of 13 dB of isolation is seen. The level of isolation is different for different isolators and it depends upon the isolator design and wheel speed. Forces and moments measured at the base for wheel with isolator and wheel without isolator clearly demonstrate and confirm a reduction in the disturbance levels of atleast one order. These isolators are further tested successfully for launch dynamic loads in order to confirm the design adequacy to sustain such loads. Results indicate that the flexible mounts of the type discussed in this thesis can be used for effective passive vibration isolation in spacecrafts with reaction/momentum wheels.

No description available.

No description available.

[ES] Los aisladores eléctricos de alta tensión desempeñan un papel fundamental de la red de distribución y transporte de energía eléctrica, pudiendo provocar fallos imprevistos de suministro eléctrico, dando lugar a importantes impactos socio-económicos. Las descargas disruptivas por contaminación o envejecimiento de los materiales amenazan continuamente la fiabilidad de la red eléctrica, constituyendo uno de los mayores retos para los diseñadores e ingenieros de mantenimiento de la red eléctrica. En la actualidad, no existen métodos eficaces para la monitorización continua de los niveles de envejecimiento de los materiales o de de contaminación en la superficie de los aisladores durante la operación normal, por lo tanto, se recurre al mantenimiento periódico de los mismos para garantizar la continuidad del suministro eléctrico. El desarrollo de una herramienta que permita monitorizar en tiempo real los depósitos de contaminación durante la operación normal proporcionaría información muy valiosa para el mantenimiento preventivo de los aisladores eléctricos de alta tensión y/o el seguimiento del estado superficial de los aisladores. La corriente de fuga registrada en los aisladores eléctricos podría utilizarse como una medida indirecta de los depósitos de contaminación. No obstante, además de por los depósitos de contaminación y el envejecimiento de los materiales, la medida de la corriente de fuga también se ve influenciada por una serie de factores ambientales, como temperatura, humedad, dirección y velocidad del viento entre otros. Por tanto, se pretende desarrollar una técnica de procesado para estimar la corriente de fuga asociada a los depósitos de contaminación (PLC) cancelando la influencia de las variables ambientales. / [CA] Els aïlladors elèctrics d'alta tensió exerceixen un paper fonamental de la xarxa de distribució i transport d'energia elèctrica, podent provocar errors imprevistos de subministrament elèctric, donant lloc a importants impactes socioeconòmics. Les descàrregues disruptives per contaminació o envelliment dels materials amenacen contínuament la fiabilitat de la xarxa elèctrica, constituint un dels reptes més grans per als dissenyadors i enginyers de manteniment de la xarxa elèctrica. En l'actualitat, no hi ha mètodes eficaços per a la monitorització contínua dels nivells d'envelliment dels materials o de de contaminació a la superfície dels aïlladors durant l'operació normal, per tant, es recorre al manteniment periòdic dels mateixos per garantir-ne la continuïtat del subministrament elèctric. El desenvolupament d"una eina que permeti monitoritzar en temps real els dipòsits de contaminació durant l"operació normal proporcionaria informació molt valuosa per al manteniment preventiu dels aïlladors elèctrics d"alta tensió i/o el seguiment de l"estat superficial dels aïlladors. El corrent de fugida registrat als aïlladors elèctrics podria utilitzar-se com una mesura indirecta dels dipòsits de contaminació. No obstant això, a més dels dipòsits de contaminació i l'envelliment dels materials, la mesura del corrent de fugida també es veu influenciada per una sèrie de factors ambientals, com ara temperatura, humitat, direcció i velocitat del vent entre d'altres. Per tant, es pretén desenvolupar una tècnica de processament per estimar el corrent de fugida associat als dipòsits de contaminació (PLC) cancel·lant la influència de les variables ambientals. / [EN] High-voltage electrical insulators play a fundamental role in the electricity distribution and transmission network, and can cause unforeseen power supply failures, giving rise to significant socio-economic impacts. Disruptive discharges due to contamination or aging of materials continually threaten the reliability of the electrical network, constituting one of the greatest challenges for designers and maintenance engineers of the electrical network. At present, there are no effective methods for the continuous monitoring of the levels of aging of the materials or of contamination on the surface of the insulators during normal operation, therefore, periodic maintenance is used to guarantee the continuity of electrical supply. The development of a tool that allows real-time monitoring of contamination deposits during normal operation would provide very valuable information for preventive maintenance of high-voltage electrical insulators and/or monitoring of the surface condition of the insulators. Leakage current recorded in electrical insulators could be used as an indirect measure of contamination deposits. However, in addition to the contamination deposits and the aging of the materials, the measurement of the leakage current is also influenced by a series of environmental factors, such as temperature, humidity, wind direction and speed, among others. Therefore, it is intended to develop a processing technique to estimate the leakage current associated with pollution deposits (PLC) canceling the influence of environmental variables. / Bueno Barrachina, JM. (2023). Contribución al mantenimiento de aisladores de alta tensión en servicio basado en medidas de corrientes de fuga [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/199256