In the thesis presented, three novel uni-planar left handed transmission lines based on Complementary Split Ring Resonators (CSRR) and Complementary Spiral Resonator (CSR) metamaterial particles are proposed for the first time and successfully applied for the performance enhancement of conventional coupled line filters and the design of a full scan leaky wave antenna. Based on the implementation of Complementary Split Ring Resonators (CSRR) a fully planar Composite Right left handed transmission line (CRLH-TL) plus a Dual Composite Right Left Handed transmission line (D-CRLH-TL) are proposed, designed and studied. The CRLH transmission line is realized loading a microstrip host line with CSRR metamaterial particles and capacitive gaps on the conductor strip of the line, while the D-CRLH transmission line is built bridging the capacitive gaps between the CSRR's with inductive connections to induce dual propagation properties in the structure. A further performance enhancement is achieved by a second proposal based on the implementation of Complementary Spiral Resonators (CSRs). The studies applied to the structure reveal that conditions for D-CRLH propagation are created in a transmission line composed only by CSR metamaterial resonant particles as the result of the unique electromagnetic properties acquired by the CSRs etched on the conductor line of a microstrip waveguide. The CSRR/CSR based D-CRLH transmission lines proposed are applied in the design of two enhanced coupled line filters. The implementation is possible for the first time in this work as result of the highly versatile layout features of the left handed transmission lines proposed which among other important geometrical features, allows couplings in both sides of the structure. Enhanced filtering features are reached by the metamaterial based coupled line filters proposed in terms of selectivity and size reduction in comparison with conventional coupled line filters. In the case of the CSRR loaded metamaterial coupled line filter a size reduction of 49% is achieved compared with a filter of similar performance. A further enhancement is reached by the second coupled filter proposed based on CSR metamaterial resonant particles. The CSR coupled filter proposed reach a roll off rate improvement of 8 dB/GHz and size reduction of 43% in comparison with a conventional coupled line filter of the same order. When this is compared against a conventional coupled line filter of similar performance but higher order, a remarkable size reduction of 77% is achieved by the proposed CSR coupled line filter. Finally, the CSR loaded D-CRLH transmission line is applied in the design of a fully planar leaky wave antenna. Using the CSR structures etched on the conductor line of a microstrip as part of the radiation mechanism altogether with the D-CRLH propagation features of the structure. A full scan radiation pattern is created with backward, forward and broadside radiation as result of the left handed propagation band, right handed propagation band and the balanced transition between them. Two leaky wave antennas are designed to operate at the centre frequencies of 12.5GHz and 6.0GHz. In order to corroborate the performance the CSR D-CRLH leaky wave antenna operating at 6.0GHz is fabricated and measured showing a scanning range of 30 deg with a maximum gain of 13.2 dBi.

This paper describes the design of a one dimensionalleaky-wave antenna, with an operating frequency at 30 GHz.The antenna consists a waveguide with one of the wallsreplaced by a semi-open row of pins, allowing power to leakout. The waveguide width and the height of the pins are taperedalong the waveguide length, in order to control the antenna’sradiation parameters.The antenna has been modeled and tested, using CST MicrowaveStudio and MathWorks Matlab. The final antenna designoperates at 30 GHz with an efficiency of 90%, side lobe levels of-26.3dB and a beamwidth 6.4°. For other frequencies in the Kaband the angle of maximum radiation varies, giving the antennascanning capabilities in one dimension. / Detta dokument beskriver utformningen aven endimensionell läckvågsantenn med en centerfrekvens på30 GHz.Antennen består av en vågledare där en av väggarna ersattsmed tappar som gör att effekt kan stråla ut. Vågledarens breddoch tapparnas höjd ändras längs vågledarens längd för attkontrollera antennens strålningsparametrar.Antennen har modellerats och testats med CST MicrowaveStudio och MathWorks Matlab. Den slutgiltiga antenndesignenfungerar vid 30 GHz med en effektivitet på 90%, sidlobsnivåerpå -26.3dB och en strålbredd på 6.4°. För andra frekvenser inomKa-bandet varierar vinkeln för maximal strålning, vilket tillåterantennen att scanna i en dimension. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

Several microwave devices and antennas that are based on negative-refractive-index transmission-line (NRI-TL) metamaterials are presented in this thesis, which exhibit superior performance features compared to their conventional counterparts. These are a Wilkinson balun, a 1:4 series power divider, a four-element printed dipole array, a leaky-wave antenna, and an electrically small folded-monopole antenna. The Wilkinson balun employs +90° and −90° NRI-TL metamaterial lines at the output branches of a Wilkinson divider, to achieve a six-fold increase in the measured differential output phase bandwidth compared to that of an analogous balun employing transmission lines, while occupying only 55% of the area. The 1:4 series power divider comprises four non-radiating 0° NRI-TL metamaterial lines, each with a compact length of λ0/8, to provide equal power split to all four output ports. Compared to a conventional series power divider employing one-wavelength long transmission lines, the metamaterial divider provides a 154% increase in the measured through-power bandwidth, while occupying only 54% of the area. The metamaterial series power dividing concept is also applied to a four-element fully-printed dipole array that is designed to radiate at broadside, in order to demonstrate that the array exhibits reduced beam squinting characteristics. It is shown that the metamaterial-fed array has a measured scan-angle bandwidth that is 173% greater than an array that is fed using a conventional low-pass loaded line. The reduced-beam squinting property that NRI-TL metamaterial lines offer is subsequently exploited to create a leaky-wave antenna that radiates a near-fixed beam in the forward +45° direction, with an average measured beam squint of only 0.031°/MHz. This is achieved by operating the antenna in the upper right-handed band where the phase and group velocities are the closest to the speed of light. Finally, an electrically small antenna comprising four 0° NRI-TL metamaterial unit cells is presented which supports a predominantly even-mode current, thus enabling it to be modeled as a multi-arm folded monopole. This significantly increases its radiation resistance, which allows it to be matched to 50 Ω, while maintaining a high measured efficiency of 70%.

Several microwave devices and antennas that are based on negative-refractive-index transmission-line (NRI-TL) metamaterials are presented in this thesis, which exhibit superior performance features compared to their conventional counterparts. These are a Wilkinson balun, a 1:4 series power divider, a four-element printed dipole array, a leaky-wave antenna, and an electrically small folded-monopole antenna. The Wilkinson balun employs +90° and −90° NRI-TL metamaterial lines at the output branches of a Wilkinson divider, to achieve a six-fold increase in the measured differential output phase bandwidth compared to that of an analogous balun employing transmission lines, while occupying only 55% of the area. The 1:4 series power divider comprises four non-radiating 0° NRI-TL metamaterial lines, each with a compact length of λ0/8, to provide equal power split to all four output ports. Compared to a conventional series power divider employing one-wavelength long transmission lines, the metamaterial divider provides a 154% increase in the measured through-power bandwidth, while occupying only 54% of the area. The metamaterial series power dividing concept is also applied to a four-element fully-printed dipole array that is designed to radiate at broadside, in order to demonstrate that the array exhibits reduced beam squinting characteristics. It is shown that the metamaterial-fed array has a measured scan-angle bandwidth that is 173% greater than an array that is fed using a conventional low-pass loaded line. The reduced-beam squinting property that NRI-TL metamaterial lines offer is subsequently exploited to create a leaky-wave antenna that radiates a near-fixed beam in the forward +45° direction, with an average measured beam squint of only 0.031°/MHz. This is achieved by operating the antenna in the upper right-handed band where the phase and group velocities are the closest to the speed of light. Finally, an electrically small antenna comprising four 0° NRI-TL metamaterial unit cells is presented which supports a predominantly even-mode current, thus enabling it to be modeled as a multi-arm folded monopole. This significantly increases its radiation resistance, which allows it to be matched to 50 Ω, while maintaining a high measured efficiency of 70%.

本論文では，遮断周波数以下のTE・TMモードを利用した右手/左手系複合円筒導波管および方形導波管を提案する．この提案したCRLH導波管にスリットまたはスロットを設けることで構成された導波管型漏洩波アンテナの放射特性について述べている．最後に，CRLH導波管を試作し解析結果と実験結果の比較を行うことで，CRLH方形・円筒導波管の構成法の有用性を明らかにする． / This paper proposes a composite right/left-handed cylindrical and rectangular waveguides using the cutoff TE and TM modes. The CRLH waveguides can be successfully applied to radiation characteristics of leaky-wave antenna by setting slits or slots. Finally, usefulness of the proposed CRLH waveguides is verified by comparison between the calculated and the measured values. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

The project main purpose is to design a prototypeof a leaky-wave antenna (LWA) which will serve as a basisto future manufacturing of a more advanced product withpotential use for an imaging radar system. The antenna consistsof Goubau line corrugations with rectangular radiation patches.Both configurations with longitudinal symmetric and glidesymmetric corrugations have been analyzed, paying specialattention to their dispersion diagrams. A parametric study ofthe dimensions of the structure has been conducted as well.Radiation patches have been added with different offsetingsbetween each other, in order to study the effect of the separationbetween patches to the radiation pattern. The frequencybeam scanning characteristic of the antenna is also shown.This antenna operates at a center frequency of 9.4 GHz, withan efficiency of 80 %. It scans over an approximate angle widthfrom -50 to 50◦ in a frequency range from 8.5 to 10.2 GHz.It has been modeled using CST Microwave Studio and Matlab. / Det huvudsakliga målet för projektet är att designa en prototyp av en läckvågsantenn (LWA) som ska verka som en grund för framtida tillverkning av mer avancerade produkter, med potentiell användning för radarsystem för bildtagning. Antennen består av en Goubau linje veckning med rektangulära strålningsflikar. Båda konfigurationerna med longitudinell symmetri och glid symmetri har analyserats. Förutom detta har en parameterstudie av dimensionerna av strukturen utförts. Strålningsflikar har blivit tillagda med olika förskjutningar mellan varandra, för att studera effekten av separationen mellan flikarna och strålningsmönstret. Egenskaperna hos antennens frekvensberoende skanning visas också. Denna antenn fungerar vid en centerfrekvens på 9.4 GHz, med en effektivitet på 80%. Den skannar över en ungefärlig vinkel från -50 till 50◦ över ett frekvensspann från 8.5 till 10.2 GHz. Detta har modellerats med CST Microwave Studio och Matlab. / Kandidatexjobb i elektroteknik 2022, KTH, Stockholm

Moving into higher frequencies, in occurrence withmodern applications, poses the issue of higher attenuation ofelectromagnetic waves, which in turn demand more directiveantennas. This paper proposes a directive antenna designoperating at 30GHz based on leaky-wave technology. Themodel consists of two main components. Firstly, a corrugatedparallel plate waveguide serves the purpose of controlling thepropagation of electromagnetic waves, in particular the guidedwavelength. Secondly, an array of continuous transverse stubsare implemented in the parallel plate waveguide, which allowsfor radiation into free space and gives a directive beam due tothe array configuration. Dispersive properties of the waveguideare studied to select appropriate dimensions for the corrugationsand optimization of the transverse stub dimensions is performedby a unit cell parameter analysis. The proposed design producepencil beam radiation in the broadside direction with a gain of24:5 dBi and a 􀀀3dB relative bandwidth of 8:8% and anaperture efficiency of 79%. / Att gå upp i frekvens för att möta krav sattaav moderna tillämpningar för med sig problemet med högreattenuering av elektromagnetiska vågor. Detta sätter i sin turkrav på mer riktade antenner för att kompensera för förlusterna.I rapporten presenteras en riktad läckande-vågsantenn för30GHz. Modellen består av två huvudsakliga komponenter.Först en korrugerad parallellplåts-vågledare, vars syfte är attkontrollera hur vågen propagerar, särskilt med avseende påvåglängd. Sedan en serie med transversella öppningar som tillåterutstrålning, där seriens utformning ger upphov till en direktivstråle. Dimensioner bestäms genom dispersionsanalys av denkorrugerade vågledaren och optimering av den strålande enhetscellensker genom en parameterstudie. Den föreslagna modellenproducerar en riktad stråle med antennvinsten 24:5 dBi, relativabandbredden 8:8% och apertureffektiviteten 79%. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

The thesis deals with basic principles of metamaterials, which exhibit unusual properties in microwave applications (e.g., negative permittivity and permeability). Different type of metamaterial antennas and parameters of such antennas are described in the thesis.

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.

La focalisation du champ électromagnétique dans les zones de champ proche et lointain est un sujet de forte actualité pour l'imagerie médicale et la radiométrie des microondes jusqu'aux ondes millimétriques. Dans ce cadre, la théorie des ondes de fuite est un formalisme élégant qui permet de décrire d'une même façon les problèmes radiatifs en champ proche et en champ lointain des microondes aux fréquences optiques. Dans cette thèse, on utilise la polyvalence de la théorie des ondes de fuite pour développer des systèmes rayonnants complexes afin de contrôler les caractéristiques radiatives en champ lointain aux fréquences submillimétriques et pour focaliser la radiation électromagnétique en champ proche aux fréquences millimétriques. Ainsi, l'utilisation de matériaux uniques comme le graphène et les cristaux liquides ont été considérés pour la conception des antennes à ondes de fuite, en obtenant des résultats très intéressants en termes de reconfigurabilité, d'efficience et de directivité. Dans ce contexte, une analyse théorique originale a fourni de nouvelles formules pour l'évaluation des caractéristiques radiatives (c.à.d. la largeur de faisceau, le niveau des lobes secondaires, etc.) des antennes à ondes de fuite. En effet, la largeur du faisceau de ces antennes est, jusqu'à présent, estimée au moyen des formules proposées pour la première fois dans les années '60 par Prof. Arthur A. OLINER. Ces formules ne tiennent en compte ni de la longueur de l'antenne (sauf pour des cas très particuliers), ni du rayonnement longitudinal, elles ne permettent donc pas une évaluation rigoureuse.En complément à la reconfigurabilité en champ lointain, les ondes de fuite offrent aussi la possibilité de focaliser la radiation en champ proche. Dans ce cas, on voit que les ondes de fuite peuvent être utilisées d'une façon efficace pour générer des faisceaux non diffractifs de Bessel à travers des systèmes rayonnants à bande étroite aux ondes millimétriques. De plus, le caractère non diffractif des faisceaux de Bessel peut aussi être utilisé pour générer des impulsions très localisées (comme les solitons en optiques) à travers la superposition continue des faisceaux de Bessel sur une large bande de fréquence. Dans ce cadre, une nouvelle formulation a été développée afin de comprendre les limitations physiques et technologiques concernant la génération des impulsions non diffractives et non dispersives, c.à.d. les X-waves. Les résultats ont montré qu'un type de systèmes rayonnants à large bande, notamment les antennes RLSA (en anglais « Radial Line Slot Array »), semblent très favorables pour la génération des X-waves. / In recent years, microwave, millimeter-wave, and THz applications such as medical and security imaging, wireless power transfer, and near-field focusing, just to mention but a few, have gained much attention in the area of ICT due to their potentially high social impact. On one hand, the need of highly-directive THz sensors with tunable radiating features in the far-field region has recently boosted the research activity in the design of flexible, low-cost and low-profile devices. On the other hand, it is of paramount importance to focus energy in the near-field region, and thus the generation of limited-diffraction waves in the microwave and millimeter-wave regime is a topic of recent increasing interest. In this context, leaky-wave theory is an elegant and extremely useful formalism which allows for describing in a common fashion guiding and radiating phenomena in both the near field and the far field, spanning frequencies from microwaves to optics passing through THz. In this PhD thesis we aim to exploit the intrinsic versatility of the leakywave approach to design advanced radiating systems for controlling the far-field radiating features at THz frequencies and for focusing electromagnetic radiation in the near field at millimeter waves. Specifically, the use of relatively new materials such as graphene and liquid crystals has been considered for the design of leaky-wave based radiators, achieving very promising results in terms of reconfigurability, efficiency, and radiating capabilities. In this context, an original theoretical analysis has provided new general formulas for the evaluation of the radiating features (e.g., half-power beamwidth, sidelobe level, etc.) of leaky-wave antennas. Indeed, the current formulations are based on several simplifying hypotheses which do not allow for an accurate evaluation of the beamwidth in different situations. In addition to the intriguing reconfigurable capabilities offered by leaky waves in far-field applications, interesting focusing capabilities can be obtained in the near field. In particular, it is shown that leaky waves can profitably be used to generate limited-diffraction Bessel beams by means of narrow-band radiators in the microwave range. Also, the use of higherorder leaky-wave modes allows for achieving almost the same performance in the millimeter-wave range, where previous designs were subjected to severe fabrication issues. Even more interestingly, the limited-diffractive character of Bessel beams can also be used to generate limited-diffraction pulses as superpositions of monochromatic Bessel beams over a considerable fractional bandwidth. In this context, a novel theoretical framework has been developed to understand the practical limitations to efficiently generate limited-diffraction, limited-dispersion pulses, such as X-waves, in the microwave/millimeter-wave range. As a result of this investigation, a class of wideband radiators has been thoroughly analyzed, showing promising capabilities for the generation of both zeroth-order and higher-order Xwaves. The latter may pave the way for the first localized transmission of orbital angular momentum in the microwave range.