Experiments on neutrino oscillations have confirmed that neutrinos have small, but non-zero masses, and that the interacting neutrino states do not have definite masses, but are mixtures of such states.The seesaw models make up a group of popular models describing the small neutrino masses and the corresponding mixing.In these models, new, heavy fields are introduced and the neutrino masses are suppressed by the ratio between the electroweak scale and the large masses of the new fields. Usually, the new fields introduced have masses far above the electroweak scale, outside the reach of any foreseeable experiments, making these versions of seesaw models essentially untestable. However, there are also so-called low-scale seesaw models, where the new particles have masses above the electroweak scale, but within the reach of future experiments, such as the LHC.In quantum field theories, quantum corrections generally introduce an energy-scale dependence on all their parameters, described by the renormalization group equations. In this thesis, the energy-scale dependence of the neutrino parameters in two low-scale seesaw models, the low-scale type I and inverse seesaw models, are considered. Also, the question of whether the neutrinos are Majorana particles, \ie , their own antiparticles, has not been decided experimentally. Future experiments on neutrinoless double beta decay could confirm the Majorana nature of neutrinos. However, there could also be additional contributions to the decay, which are not directly related to neutrino masses. We have investigated the possible future bounds on the strength of such additional contributions to neutrinoless double beta decay, depending on the outcome of ongoing and planned experiments related to neutrino masses. / QC 20110812

Yes / This paper presents a novel on-chip antenna using standard CMOS-technology based on metasurface implemented on two-layers polyimide substrates with a thickness of 500 μm. The aluminium ground-plane with thickness of 3 μm is sandwiched between the two-layers. Concentric dielectric-rings are etched in the ground-plane under the radiation patches implemented on the top-layer. The radiation patches comprise concentric metal-rings that are arranged in a 3 × 3 matrix. The antennas are excited by coupling electromagnetic energy through the gaps of the concentric dielectric-rings in the ground-plane using a microstrip feedline created on the bottom polyimide-layer. The open-ended feedline is split in three-branches that are aligned under the radiation elements to couple the maximum energy. In this structure, the concentric metal-rings essentially act as series left-handed capacitances CL that extend the effective aperture area of the antenna without affecting its dimensions, and the concentric dielectric rings etched in the ground-plane act as shunt left-handed inductors LL, which suppress the surface-waves and reduce the substrates losses that leads to improved bandwidth and radiation properties. The overall structure behaves like a metasurface that is shown to exhibit a very large bandwidth of 0.350–0.385 THz with an average radiation gain and efficiency of 8.15dBi and 65.71%, respectively. It has dimensions of 6 × 6 × 1 mm3 that makes it suitable for on-chip implementation. / 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 fnancial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1. / Research Development Fund Publication Prize Award winner, March 2020

I denna avhandling studeras elektromagnetisk vågutbredning i graderade materialkompositer med extraordinära egenskaper. Två sådana materialkompositsystem studeras särskilt, med hjälp av både analytiska och beräkningstekniska elektromagnetiska metoder. Det första systemet används för utvecklingen av en lovande icke-invasiv metod för cancerbehandling, som bygger på att tumören med insatta guldnanopartiklar värms upp med hjälp av mikrovågsstrålning. En vågledarstruktur föreslås bestående av ett tunt dielektriskt skikt med en kontinuerlig graderad materialövergång till dess omgivande material till vardera sidan av skiktet. Det tunna lagret består av cancervävnad med insatta guldnanopartiklar som drivs in i elektroforetisk svängning med hjälp av elektromagnetisk strålning. Analytiska lösningar för det givna vågledarproblemet erhålls, vilket möjliggör beräkning av absorptionskoefficienterna endast inom det tunna skiktet, vilket är viktigt för bedömning av genomförbarheten av den tänkta medicinska tillämpningen. De dispersiva dielektriska modellerna som beskriver de elektromagnetiska egenskaperna hos de relevanta biologiska vävnaderna föreslås och diskuteras. Numeriska simuleringar gjorda i COMSOL Multiphysics är i utmärkt överensstämmelse med och validerar de analytiska resultaten. Det andra systemet involverar vågutbredning från ett högerhänt material till ett vänsterhänt metamaterial i fri rymd. De två materialen är impedansmatchade, vilket säkerställer ingen reflektion, och det graderade gränssnittet mellan dem beskrivs av en kontinuerlig funktion. Metamaterialkompositer med rumsligt varierande materialparametrar har fått ett ökande teoretiskt och experimentellt intresse de senaste två decennierna. De är användbara för ett antal tillämpningar, såsom transformationsoptik. I denna uppsats diskuteras egenskaperna hos vänsterhänta material. Fältlösningarna till det impedansmatchade graderade gränssnittet härleds, och en numerisk modell utvecklas i COMSOL. Resultaten bekräftar de extraordinära egenskaperna hos vänsterhänta material. / In this thesis, electromagnetic wave propagation in graded material composites with extraordinary properties are studied. Two such material composite systems are studied in particular, using both analytical and computational electromagnetic methods. The first system is used for the development of a promising non-invasive method of cancer treatment based on heating the tumors with inserted gold nanoparticles by means of microwave radiation. A waveguide structure is proposed consisting of a thin dielectric layer with a continuous graded material transition to its surrounding materials to either side of the layer. The thin layer consists of cancer tissue with inserted gold nanoparticles that are driven into electrophoretic oscillation by means of electromagnetic radiation. Analytical solutions for the given waveguide problem are obtained, allowing the calculation of the absorption coefficients within the thin layer only, which is important for assessment of the feasibility of the envisioned medical application. The dispersive dielectric models describing the electromagnetic properties of the relevant biological tissues are proposed and discussed. Numerical simulations done in COMSOL Multiphysics are in excellent agreement with and validate the analytical results. The second system involves wave propagation from a right-handed material to a left-handed metamaterial in an open boundary system. The two materials are impedance-matched, thus ensuring no reflection, and the graded interface between them is described by a continuous function. Metamaterial composites with spatially varying material parameters have been given an increasing theoretical and experimental interest the last two decades. They are useful for a number of applications, such as transformation optics. In this thesis, the properties of left-handed media are discussed. The field solutions to the impedance-matched graded interface are derived, and a numerical model is developed in COMSOL. The results confirm the extraordinary properties of left-handed media. / <p>QC 20221129</p>

Yes / A feasibility study of a novel configuration for a super-wide impedance planar antenna is presented based on a 2 × 2 microstrip patch antenna (MPA) using CST Microwave Studio. The antenna comprises a symmetrical arrangement of four-square patches that are interconnected to each other with cross-shaped high impedance microstrip lines. The antenna array is excited through a single feedline connected to one of the patches. The proposed antenna array configuration overcomes the main drawback of conventional MPA with a narrow bandwidth that is typically <5%. The antenna exhibits a super-wide frequency bandwidth from 20 GHz to 120 GHz for S11 < −15 dB, which corresponds to a fractional bandwidth of 142.85%. The antenna’s performance of bandwidth, impedance match, and radiation gain were enhanced by etching slots on the patches. With the inclusion of the slot, the maximum radiation gain and efficiency of the MPA increased to 15.11 dBi and 85.79% at 80 GHz, which showed an improvement of 2.58 dBi and 12.54%, respectively. The dimension of each patch antenna was 4.3 × 5.3 mm2 . The results showed that the proposed MPA is useful for various existing and emerging communication systems such as ultra-wideband (UWB) communications, RFID systems, massive multiple-output multiple-input (MIMO) for 5G, and radar systems. / This work was partially supported by the Innovation Program under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

Yes / In this review paper, a comprehensive study on the concept, theory, and applications of composite right/left-handed transmission lines (CRLH-TLs) by considering their use in antenna system designs have been provided. It is shown that CRLH-TLs with negative permittivity (ε <; 0) and negative permeability (μ <; 0) have unique properties that do not occur naturally. Therefore, they are referred to as artificial structures called “metamaterials”. These artificial structures include series left-handed (LH) capacitances (C L ), shunt LH inductances (L L ), series right-handed (RH) inductances (LR), and shunt RH capacitances (CR) that are realized by slots or interdigital capacitors, stubs or via-holes, unwanted current flowing on the surface, and gap distance between the surface and ground-plane, respectively. In the most cases, it is also shown that structures based on CRLH metamaterial-TLs are superior than their conventional alternatives, since they have smaller dimensions, lower-profile, wider bandwidth, better radiation patterns, higher gain and efficiency, which make them easier and more cost-effective to manufacture and mass produce. Hence, a broad range of metamaterial-based design possibilities are introduced to highlight the improvement of the performance parameters that are rare and not often discussed in available literature. Therefore, this survey provides a wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers. To analyze the critical features of metamaterial theory and concept, several examples are used. Comparisons on the basis of physical size, bandwidth, materials, gain, efficiency, and radiation patterns are made for all the examples that are based on CRLH metamaterialTLs. As revealed in all the metematerial design examples, foot-print area decrement is an important issue of study that have a strong impact for the enlargement of the next generation wireless communication systems. / This work was supported in part by the Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER, UE) under Grant RTI2018-095499-B-C31, in part by the Innovation Programme under Grant H2020-MSCA-ITN-2016 SECRET-722424, and in part by the financial support from the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/E022936/1.

The standard model of particle physics can excellently describe the vast majorityof data of particle physics experiments. However, in its simplest form, it cannot account for the fact that the neutrinos are massive particles and lepton flavorsmixed, as required by the observation of neutrino oscillations. Hence, the standardmodel must be extended in order to account for these observations, opening up thepossibility to explore new and interesting physical phenomena. There are numerous models proposed to accommodate massive neutrinos. Thesimplest of these are able to describe the observations using only a small numberof effective parameters. Furthermore, neutrinos are the only known existing particleswhich have the potential of being their own antiparticles, a possibility that isactively being investigated through experiments on neutrinoless double beta decay.In this thesis, we analyse these simple models using Bayesian inference and constraintsfrom neutrino-related experiments, and we also investigate the potential offuture experiments on neutrinoless double beta decay to probe other kinds of newphysics. In addition, more elaborate theoretical models of neutrino masses have beenproposed, with the seesaw models being a particularly popular group of models inwhich new heavy particles generate neutrino masses. We study low-scale seesawmodels, in particular the resulting energy-scale dependence of the neutrino parameters,which incorporate new particles with masses within the reach of current andfuture experiments, such as the LHC. / Standardmodellen för partikelfysik beskriver den stora majoriteten data från partikelfysikexperimentutmärkt. Den kan emellertid inte i sin enklaste form beskrivadet faktum att neutriner är massiva partiklar och leptonsmakerna är blandande,vilket krävs enligt observationerna av neutrinooscillationer. Därför måste standardmodellenutökas för att ta hänsyn till detta, vilket öppnar upp möjligheten att utforska nya och intressanta fysikaliska fenomen. Det finns många föreslagna modeller för massiva neutriner. De enklaste av dessakan beskriva observationerna med endast ett fåtal effektiva parametrar. Dessutom är neutriner de enda kända befintliga partiklar som har potentialen att vara sinaegna antipartiklar, en möjlighet som aktivt undersöks genom experiment på neutrinolöst dubbelt betasönderfall. I denna avhandling analyserar vi dessa enkla modellermed Bayesisk inferens och begränsningar från neutrinorelaterade experiment och undersöker även potentialen för framtida experiment på neutrinolöst dubbelt betasönderfall att bergänsa andra typer av ny fysik. Även mer avancerade teoretiska modeller för neutrinomassor har föreslagits, med seesawmodeller som en särskilt populär grupp av modeller där nya tunga partiklargenererar neutrinomassor. Vi studerar seesawmodeller vid låga energier, i synnerhetneutrinoparametrarnas resulterande energiberoende, vilka inkluderar nya partiklarmed massor inom räckh°all för nuvarande och framtida experiment såsom LHC. / <p>QC 20130830</p>

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abstract The focus of this thesis is to study direction of arrival (DoA) estimation algorithms for reconfigurable leaky-wave antennas and advanced antenna arrays. Directional antennas can greatly improve the spectrum reuse, interference avoidance, and object and people localization. DoA estimation algorithms have also been shown to be useful for applications such as positioning for user tracking and location-based services in wireless local area networks (WLANs). The main goal is to develop novel DoA estimation algorithms for both advanced antenna arrays and composite right/left-handed (CRLH) leaky-wave antennas (LWAs). The thesis introduces novel modifications to existing DoA estimation algorithms and shows how these can be modified for real-time DoA estimation using both antenna types. Three modified DoA estimation algorithms for CRLH-LWAs are presented: 1) modified multiple signal classification (MUSIC), 2) power pattern cross-correlation (PPCC), and 3) adjacent power pattern ratio (APPR). Additionally, the APPR algorithm is also applied to advanced antenna arrays. The thesis also presents improvements to the modified MUSIC and APPR algorithms. The complexity of the algorithms is reduced by selecting a smaller number of received signals from different directions. The results show that the selection of the radiation patterns is very important and that the proposed algorithms can successfully estimate the DoA, even in a real-world environment. Based on the results, this thesis provides a good starting point for future research of DoA estimation algorithms to enhance the performance of future-generation wireless networks and the accuracy of localization. / Tiivistelmä Tässä väitöskirjassa tutkitaan suunnanestimointialgoritmeja uudelleen konfiguroituville vuotoaaltoantenneille (LWA, leaky wave antenna) ja kehittyneille antenniryhmille. Suuntaavilla antenneilla voidaan parantaa huomattavasti spektrin uudelleen käyttöä ja esineiden ja ihmisten sijaintipaikannusta sekä pienentää häiriöitä. Suunnanestimointialgoritmit ovat myös osoittautuneet hyödylliseksi esimerkiksi seuranta- ja sijaintipaikannuspalvelusovelluksille langattomissa lähiverkoissa. Työn päätavoite on kehittää uusia suunnanestimointialgoritmeja sekä kehittyneille antenniryhmille että vuotoaaltoantenneille (composite right/left-handed (CRLH) LWA). Työssä osoitetaan, miten olemassa olevia suunnanestimointialgoritmeja voidaan muokata uudella tavalla, jotta ne soveltuisivat molemmille antennityypeille reaaliaikaiseen suunnanestimointiin. Vuotoaaltoantennille on kehitetty kolme erilaista suunnanestimointialgoritmia: 1) muunneltu MUSIC- (multiple signal classification), 2) säteilykyvioiden tehojen ristikorrelaatio- (PPCC, power pattern cross correlation) ja 3) vierekkäisten säteilykuvioiden tehosuhdealgoritmi (APPR, adjacent power pattern ratio). APPR-algoritmia on myös käytetty kehittyneelle antenniryhmälle. Työssä esitetään myös parannuksia muunnelluille MUSIC- ja APPR-algoritmeille. Algoritmien kompleksisuutta voidaan pienentää valitsemalla vähemmän vastaanotettuja signaaleja. Tulokset osoittavat, että signaalien valinta on hyvin tärkeää ja ehdotetut algoritmit estimoivat onnistuneesti saapuvan signaalin suunnan todellisessa mittausympäristössä. Yhteenvetona voidaan sanoa, että tämä väitöstyö on hyvä lähtökohta suunnanestimointialgoritmitutkimukselle, jonka tavoitteena on parantaa tulevien sukupolvien langattomien verkkojen suorituskykyä ja paikannuksen tarkkuutta.

Le travail de cette thèse est en rapport avec les métamatériaux et ses applications. Tout d’abord, un état de l’art est dressé en présentant leur évolution depuis leur apparition en 19ème siècle jusqu’au nos jours. Les notions sur les milieux chirale, bi-anisotrope, cristaux photoniques et quelques applications dans ces milieux sont données. Ensuite, nous présentons les équations classiques de Maxwell dans les milieux complexes. L’effet bi-anisotrope dans les métamatériaux est ensuite validé par l’extraction des paramètres caractéristiques du matériau main gauche (LHM). La validation a été faite en utilisant deux types différents du résonateur avec inclusion (SRR). Les métamatériaux sont également étudiés comme des cristaux photoniques quand les dimensions utilisées sont de l’ordre de la longueur d’onde correspondant.De plus, les résonateurs SRR et multi-SRR sont analysés du point de vue analytique et électromagnétique afin d’extraire leur fréquence de résonance. Par conséquent, ces composants peuvent être introduits dans différents types de conception; La surface conductrice magnétique artificielle (AMC) illustre un cas explicite et efficace de ces derniers. Une antenne dipôle, placée sur cette surface à la place d’un plan de masse conventionnel, a été étudiée comme une application des métamatériaux. Les résultats relatifs sur la directivité, le gain et le coefficient de réflexion montrent une nette amélioration. Une antenne multi-bandes, comme une autre application des métamatériaux, a également été conçue et simulée. Le résonateur SRR est inséré dans l’antenne de départ afin de créer une autre résonance, et par conséquent une autre bande est ainsi créée. / The work in this thesis deals with metamaterials, its components and applications. A historical overview about these materials, features and researches in the domain are presented. Chiral media, binaisotropic materials and photonic crystals are also studied in order to visualize physics behind metamaterials.Electromagnetic properties in complex media are widely investigated. Starting from Maxwell’s equations, bi-anisotropic materials and their effect are deeply analyzed whereas two types of Split Ring Resonator (SRR) are treated to determine constitutive parameters of Left Handed Materials (LHM). The metamaterials are also studied as photonic crystals since the effective medium approach is not applicable when the dimensions of the inclusions tend to the operating wavelength.Moreover, SRRs and Multi SRRs are synthesized analytically and electromagnetically in order to extract their resonant frequencies. Consequently, these components could be introduced in any design; Artificial Magnetic Conductor (AMC) surface is an efficient case. Thus, a low profile antenna positioned over such surface is examined as an application of metamaterials. The results of directivity, gain and reflection coefficient are of great importance and affirm the employing of metamaterials in such applications. A dual band PCB antenna, as another application of metamaterials, is designed and simulated. The SRR element studied in the previous chapters is used as the trap which inserted in the arm of the antenna in order to create another resonance, and consequently another band is created.