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No / This paper proposes a tuneable band-rejected miniaturised monopole antenna. The band-notching was achieved by printing an inner chorded crescent shape over the surface of the substrate. By placing a small varactor between the inner and outer arches, the centre frequency of each notch can be individually shifted downwards. The design of the proposed structure has a controllable rejection in the range from 2.38 to 3.87 GHz maintaining a wideband performance from 1.5 to 5 GHz based on VSWR ≤ 2. The antenna prototype was fabricated and tested. Simulated and measured results are performed and analysed. With a compact size, the proposed monopole antenna may well work as an internal antenna in a portable device.

The objective of this thesis is to present a theoretical and experimental investigation of the dynamics of micro and nano-electromechanical systems electrothermally tuned and electrostatically actuated, and explore their potential for practical applications. The first part of the dissertation presents the tuning of the frequency of clamped-clamped micro and nano-resonators, straight and curved. These resonators are electrothermally or electrostatically tuned. The effect of geometric parameters on the frequency variation is investigated experimentally and theoretically using a reduced order model based on the Euler-Bernoulli beam theory. High tunability is demonstrated for micro and nano beams, straight and initially curved. The second part discusses the dynamical behavior of a curved (arch) beam electrothermally tuned and electrostatically actuated. We show that the first resonance frequency increases up to twice its fundamental value and the third resonance frequency decreases until getting very close to the first resonance frequency triggering the veering phenomenon. We study experimentally and analytic ally, using the Galerkin procedure, the dynamic behavior of the arch beam. Next, upon changing the electrothermal voltage, the second symmetric natural frequency of the arch is adjusted to near twice, three times, and four times the fundamental natural frequency. This gives rise to a potential two-to-one, three-to-one, and four-to-one autoparametric resonances between the two modes. These resonances are demonstrated experimentally and theoretically. The third part of the dissertation is concerned with the incorporation of the electrothermally tuned and electrostatically actuated microresonators into potential applications: filtering and sensing. First, we experimentally prove an exploitation of the nonlinear softening, hardening, and veering phenomena of an arch beam, to demonstrate a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage. Second, a pressure sensor based on the convective cooling of the air surrounding an electrothermally heated resonant bridge is demonstrated experimentally. The concept is demonstrated using both straight and arch microbeam resonators driven and sensed electrostatically. The change in the surrounding pressure is shown to be accurately tracked by monitoring the change in the resonance frequency of the structure.

Predicting and verifying the tunable optical properties of metal nanostructures is central to designing materials optimized for specific applications. Chemically- deposited nanostructures have been well-studied near the percolation threshold, but at lower surface coverages they exhibit sample-to-sample variations in the optical response. We identify how these variations are driven by the high variability in the particle size distribution in a particular surface coverage range. We then explore film- coupled nanoparticle systems consisting of a silver nanoparticle, thin dielectric spacer layer, and flat silver film, to enable tuning toward the blue and green parts of the spectrum. We use the boundary element method to visualize charge distributions of various resonances. We fabricate samples using thermal evaporation and spin coating methods, and use polarized reflectance spectroscopy to measure their optical response at an ensemble level. We achieve a 532nm resonance for 80nm silver nanoparticles on 13nm PMMA spacers and 100nm silver thin films. The resulting design is a candidate for enhancing fluorescence in a new spectral range. This dissertation includes previously unpublished co-authored material.

Le but de la thèse est de réaliser des filtres accordable en technologie planaire multi-niveaux proposé par l'entreprise allemande IHP. Les filtres sont réalisés aux ondes millimétriques,principalement autour de 60 GHz et 140 GHz. Nous étudions l'accordabilité en fréquence mais aussi l'accordabilité en bande passante ne utilisant un concept nouveau établie au cours de cette thèse. Les premiers résultats concernant les filtres accordables en fréquence ont permit la rédaction de plusieurs articles. Maintenant, nous venons de recevoir les mesures prouvant notre nouveau concept permettant l'accord en fréquence et en bande passante des filtres planaires à base de résonateurs en anneau / The thesis aim is to realize tunable filters using the BiCMOS planar technologie provided by thegerman company IHP. We are working on millimeterwaves, mainly 60 GHz and 140 GHz. Westudy the frequency tunability but also the bandwidth tunability using a new concept provided bythe study carried during this thesis. The first study about frequency tunability aimed to severalconference articles. Now, we just have the measurements proving the new concept of frequencycontrol while maintening a bandwidth control of planar ring filters

The dependence of dielectric permittivity on the applied electric field, high dielectric constant and low cost makes barium strontium titanate (BST) a promising ferroelectric material for applications in tunable microwave devices. High tunability and low dielectric loss is desired for tunable microwave devices. The primary objective of this research was to optimize the tunability and dielectric loss of BST thin films at microwave frequencies with different deposition techniques. Ba0.5Sr0.5TiO3 thin films were grown on Pt/TiO2/SiO2/Si, by pulsed laser deposition (PLD) and sputtering. Parallel plate capacitor structures were designed using ADS and fabricated. The microstructural and phase analysis of the BST films were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. The analysis of surface morphology was done using atomic force microscopy. Electrical properties of parallel plate capacitors were measured using LCR meter and tunability of 2.4:1 and loss tangent of 0.05 was achieved at low frequencies for laser deposited BST thin films. Tunability of 2.8:1 and loss tangent of 0.03 was achieved at low frequencies for sputtered BST thin films. The correlation of optimized structural and dielectric properties of thin films deposited by pulsed laser deposition and sputtering technique was analyzed and compared. The structural characterization of sputtered BST thin film on MgO, Alumina and LaAl2O3 was achieved for the fabrication of interdigital capacitors. Interdigital capacitor has been designed using ADS momentum.

Des propriétés électromagnétiques nouvelles peuvent être réalisées à l'aide d'une méta-surface à travers des structures artificielles. La permittivité et la perméabilité effectives d'une méta-surface peuvent être conçues de façon flexible et même accordées de sorte à présenter des réponses électromagnétiques pouvant être très différentes de celles de leurs homologues naturels, ce qui conduit à des propriétés améliorées voire parfois à un comportement extraordinaire. Cette thèse porte sur la conception, la fabrication et l'expérimentation de méta-surfaces micro-fluidiques pour le contrôle de propriétés des ondes électromagnétiques. Leur réalisation est basée sur des technologies relevant de la photolithographie et de la micro-fluidique, mises en œuvre sur des substrats souples d'épaisseur sub-longueur d'onde. Plus spécifiquement, nous avons exploité l'incorporation de divers matériaux dans un réseau de canaux micro-fluidiques, y compris des diélectriques liquides, un métal liquide et un métal solide pour manipuler davantage les réponses électromagnétiques des méta-surfaces correspondantes, telles que l'absorption, la transmission et la chiralité. La première partie de la thèse présente une méta-surface très absorbante sur une ultra-large bande spectrale et. Elle est constituée d'un réseau de résonateurs formés de gouttelettes d'eau noyées dans le matériau diélectrique souple, le PDMS; l’absorption mesurée est presque parfaite sur les bandes Ku, K et Ka. La seconde partie de la thèse porte sur un absorbeur agile et indépendant de l'angle dans la gamme Térahertz ; il s’agit d’une méta-surface à base de métal liquide, où un réseau de puits métalliques liquides dont la hauteur est contrôlée de façon continue, ce qui brise la limitation d'accordabilité dans le plan 2D. La troisième partie de la thèse porte sur une méta-surface chirale active. La méta-surface peut être commutée de achiral à chiral en déformant la structure en spirale initialement plane vers une géométrie 3D. Cette fonctionnalité peut manipuler la transmission hyperfréquence de symétrique à asymétrique sous incidence avant et arrière. En conclusion, l'optimisation de l'absorption, de la transmission et de la chiralité d’ondes électromagnétiques a été réalisée grâce à des méta-surfaces micro-fluidiques, qui semblent ainsi présenter un important potentiel applicatif dans divers domaines tels que la technologie furtive, l'imagerie et la communication optique / Novel and tailored electromagnetic properties can be realized using a metasurface through artificially designed structures. The effective permittivity and permeability of a metasurface can be flexibly designed and even tuned so as to exhibit electromagnetic responses that can be very different from those of their natural counterparts, leading to enhanced properties and sometimes to extra-ordinary behaviour. This thesis focuses on the design, fabrication and experimentation of meta-liquid-based metasurfaces for electromagnetic wave control and modulation. These metasurfaces are based on the use of both photolithography-based microfabrication and microfluidic technologies implemented onto thin and flexible substrates of sub-wavelength thickness. More specifically, the incorporation within a microfluidic channel network of various materials, including liquid dielectric material, liquid metal and solid metal have been exploited to further manipulate the electromagnetic responses of the related metasurfaces, such as the absorption, transmission and chirality. The first part of the thesis reports an ultra-broadband and wide-angle absorbing material by water-resonator-based metasurface. It consists of an array of water droplets embedded in the soft dielectric material, PDMS; it exhibited an almost perfect absorptivity over the Ku, K and Ka bands. The second part of the thesis focuses on a frequency-agile and wide-angle absorber in terahertz by liquid-metal-based metasurface, where a liquid-metal-pillar array can be continuously controlled in the vertical direction hence breaking the tuning limitation in the 2D plane. The third part of the thesis focuses on an active chiral metasurface. The metasurface can be switched from achiral to chiral by changing the spiral structure from planar pattern to 3D pattern. This functionality can manipulate the microwave transmission from symmetric to asymmetric under forward and backward incidence. In conclusion, tunability on the absorption, transmission and chirality have been realized through microfluidic metasurfaces, which appear having high potential applications in various areas such as stealth technology, imaging system, and optical communication, to name a few

Abstract The thesis describes electrically tunable microwave devices utilising low sintering temperature, screen printable Barium Strontium Titanate (BST) thick films. The work has been divided into two parts. In the first section, the fabrication and microwave characterisation of BST material based structures compatible with Low Temperature Cofired Ceramic technology (BST-LTCC) are presented. Three different fabrication techniques, namely: direct writing, screen printing and via filling techniques, were used for the realisation of the structures. A detailed description of these fabrication techniques is presented. The dielectric properties such as relative permittivity, static electric field dependent tunability and loss tangent of BST-LTCC structures at microwave frequencies were characterised using coplanar waveguide transmission line and capacitive element techniques. The measured dielectric properties of BST-LTCC structures realised with the different fabrication methods are presented, compared and discussed. The second section describes tunable microwave devices based on BST-LTCC structures. A frequency tunable folded slot antenna (FSA) with a screen printed, integrated BST varactor is presented. The resonant frequency of the FSA was tuned by 3.2% with the application of 200 V external bias voltage. The impact of the BST varactor on the total efficiency of the antenna was studied through comparison with a reference antenna not incorporating the BST varactor. A compact, frequency tunable ceramic planar inverted-F antenna (PIFA) utilising an integrated BST varactor for mobile terminal application is presented. The antenna's resonant frequency was tuned by 3% with an application of 200 V bias voltage. Frequency tunable antennas with a completely integrated electrically tunable BST varactor with silver metallisation are introduced in this work for the first time. The integration techniques which are described in this thesis have not been previously reported in scientific literature. The last part of the thesis presents a microwave delay line phase shifter operating at 3 GHz based on BST-LTCC structures. The figure of merit (FOM) of the phase shifter was measured to be 14.6 °/dB at 3 GHz and and the device employs a novel structure for its realisation that enabled the required bias voltage to be decreased, while still maintaining compliance with standard screen printing technology. The performance of the phase shifter is compared and discussed with other phase shifters realised with the BST thick film process. The applications of BST-LTCC structures were demonstrated through frequency tuning of antennas, varactors, and phase shifters. The low sintering temperature BST paste not only enables the use of highly conductive silver metallisation, but also makes the devices more compact and monolithic.

Abstract The recent trend in low temperature co-fired ceramic (LTCC) technology is to integrate more elements into multilayer modules. This thesis describes work specifically aimed at developing ferroelectric barium strontium titanate (BST) for integration into such modules. In particular, an objective was the development of a novel, electric field controlled, tunable component to be used at microwave frequencies (2–26 GHz). For the application envisaged, relative permittivity is required to be low (100–1000) and adjustable by a suitable applied electric field, the dissipation factor at room temperature must be low (~0.001) at 2–26 GHz, and most importantly, the sintering temperature must be suited to the LTCC technology (~900 °C) Initial work was focused on sol-gel derived Ba0.7Sr0.3TiO3 powders with boron oxide addition, which were sintered at 900 °C, the dissipation factor was 0.006. The dissipation factor was not low enough for the desired microwave application, and attention turned to powders prepared by the mixed-oxide route. The Ba0.7Sr0.3TiO3 powders, fluxed with the optimum amounts of boron oxide and lithium carbonate, could be sintered at 890 °C to the same density as is achieved with un-fluxed Ba0.7Sr0.3TiO3 sintered at 1360 °C. The dissipation factor for this fluxed powder was acceptably low, although permittivity was too high for the particular objective. Subsequently, research was on BST modified by magnesia, 0.4Ba0.55Sr0.45TiO3-0.6MgO (BSTM). With the optimum fluxing additives, the sintering temperature necessary to achieve a dense BSTM-based ceramic was reduced to 950 °C. The developed microstructure was good, and the relative permittivity and dissipation factor values (221, 0.0012 at 1 kHz) at room temperature indicated good microwave properties. Studies were also undertaken with organic-based tape-casting slurries, laminating procedures and burn-out and sintering schedules. Several kinds of tapes were fabricated and characterized. A test structure for the measurement of dielectric properties at 26 GHz of the optimized BSTM-based ceramic was constructed. The specimen was 50 μm thick layer of BST on an alumina substrate. The relative permittivity and tunability were 130 and >15 % at 4 V μm-1 at room temperature. A tunable phase-shifter was fabricated from the same BSTM-based tape using a novel gravure printing technique, and measurements at 26 GHz showed phase shift from 10 to 35° when the electric field was increased from 1 V μm-1 to 2.5 V μm-1. Some exploratory experiments are described to assess the compatibility of the developed BST-based LTCC with commercial LTCC and some electroceramics.

This thesis will explore the ultrafast modulation and optical tunability of plasmonic filters in the terahertz (THz) spectral region. First, the principles and functional design of THz metasurfaces are explored through plasmonic surface lattice resonance interactions and lumped-element circuit models. We will then describe the methodology of generating and detecting THz radiation through the nonlinear processes of optical rectification and electrooptic sampling, respectively. Next, the implementation of a THz time-domain spectroscopy technique is discussed in the context of pump-probe measurements and time-domain resonance analysis. We then show how THz probed materials can be characterized in terms of a temporal and spectral analysis. We will demonstrate how this time-domain technique can allow us to characterize the interaction of plasmonic resonators with optically active substrates and 2D nanomaterials. A completely tunable THz plasmonic notch resonance is modulated utilizing a static and dynamic method of optical tunability in silicon. Active tunability is also demonstrated in a graphene-based plasmonic resonator through the hot carrier multiplication effect. The significance of this work lies in the application of designing controllable devices for future THz communication technologies.