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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Microwave near-field probes to detect electrically small particles

Ren, Zhao 06 November 2014 (has links)
Microwave near-field probes (MNPs) confine evanescent fields to regions that are substantially smaller than the wavelength at the operation frequency. Such probes are able to resolve subwavelength features, thus providing resolution much higher than the classical Abb?? limit. These abilities of MNPs are primarily due to the evanescent nature of the field generated at the tip of the probes. In the past, MNPs with ultra-high resolution were designed by tapering a resonant opening to provide high field concentration and high sensitivity. The limitations of these MNPs were subject to low surface roughness and practical realization challenges due to their geometrical features and vibration control constraints. Metamaterials with their ability to enhance evanescent fields, lead to the speculation that they could potentially increase the sensitivity of near-field probe. Periodically arranged metamaterial unit elements such as split-ring-resonators (SRRs) can create negative permeability media. Placing such material layer in the proximity of a probe leads to enhancement of the evanescent waves. Guided by this remarkable feature of metamaterials, I proposed an MNP consisting of a wire loop concentric with a single SRR. The evanescent field behavior of the probe is analyzed using Fourier analysis revealing substantial enhancement of the evanescent field consistent with metamaterial theory predictions. The resolution of the probe is studied to especially determine its ability for sub-surface detection of media buried in biological tissues. The underlying physics governing the probe is analyzed. Variations of the probe are developed by placement of lumped impedance loads. To further increase the field confinement to smaller region, a miniaturized probe design is proposed. This new probe consists of two printed loops whose resonance is tunable by a capacitor loaded in the inner loop. The sensing region is decreased from ??/20 to ??/55, where ?? is the wavelength of the probe???s unloaded frequency. The magnetic-sensitive nature of the new probe makes it suitable for sensing localized magnetostatic surface resonance (LMSR) occurring in electrically very small particles. Therefore, I proposed a sensing methodology for detecting localized magnetostatic surface (LMS) resonant particles. In this methodology, an LMS resonant sphere is placed concentrically with the loops. A circuit model is developed to predict the performance of the probe in the presence of a magnetic sphere having Lorentz dispersion. Full-wave simulations are carried out to verify the circuit model predictions, and preliminary experimental results are demonstrated. The Lorentzian fit in this work implies that the physical nature of LMSR may originate from spin movement of charged particle whose contribution to effective permeability may be analogous to that of bound electron movement to effective permittivity in electrostatic resonance. Detection of LMSR can have strong impact on marker-based sensing applications in biomedicine and bioengineering.
92

Investigation of RF Direct Detection Architecture Circuits for Metamaterial Sensor Applications

Suwan, Na'el January 2011 (has links)
Recent advances in metamaterials research has enabled the development of highly sensitive near-field microwave sensors with unprecedented sensitivity. In this work, we take advantage of the increase in the sensitivity to produce a compact, lightweight, affordable, and accurate measurement system for the applications of microwave imaging and material characterization. This sensitivity enhancement due to the inclusion of metamaterials opens the door for the use of inexpensive microwave components and circuits such as direct detectors while leveraging the high sensitivity of the metamaterial probe to deliver an overall accurate measurement system comparable to that of a traditional probe used in conjunction with a vector network analyzer. The sensor developed is composed of a metamaterial sensor with an RF direct detection circuit. In this work, two prototype measurement systems have been designed and tested. Measurement of small cracks in conductors and material characterization using the proposed system were performed. The results from the newly developed sensors were compared with the results from vector network analyzer measurements. Good agreement was obtained. The feasibility of a compact, lightweight, affordable, and accurate system has been demonstrated by using the developed prototypes.
93

Estudo da interfer?ncia de uma metasuperf?cie no desempenho das antenas de microfita

Santos, Rafael Celestino dos 16 December 2016 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-20T19:50:21Z No. of bitstreams: 1 RafaelCelestinoDosSantos_DISSERT.pdf: 2928154 bytes, checksum: ed85070c1f646df9265898c17421fbdd (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-03-22T19:46:13Z (GMT) No. of bitstreams: 1 RafaelCelestinoDosSantos_DISSERT.pdf: 2928154 bytes, checksum: ed85070c1f646df9265898c17421fbdd (MD5) / Made available in DSpace on 2017-03-22T19:46:13Z (GMT). No. of bitstreams: 1 RafaelCelestinoDosSantos_DISSERT.pdf: 2928154 bytes, checksum: ed85070c1f646df9265898c17421fbdd (MD5) Previous issue date: 2016-12-16 / Este trabalho tem por objetivo apresentar a influ?ncia de uma metasuperf?cie, um tipo especial dos metamateriais, no desempenho das antenas de microfitas. As metasuperf?cies s?o materiais artificiais que n?o s?o encontrados em sua forma convencional na natureza e apresentam caracter?sticas eletromagn?ticas n?o convencionais, como o ?ndice de refra??o e os coeficientes de permissividade el?trica e permeabilidade magn?tica negativos o que provocam efeitos eletromagn?ticos atrativos para diversas aplica??es, como por exemplo: melhorar a performance de uma antena de microfita como ser? mostrado nesse trabalho. Iniciaremos o trabalho mostrando um breve hist?rico, defini??es e propriedades eletromagn?ticas das antenas, antenas de microfita, metamateriais e das metasuperf?cies. Em seguida, iremos projetar e confeccionar uma antena de microfita com e sem a utiliza??o de uma metasuperf?cie onde simularemos atrav?s do software HFSS Ansoft Designer e testaremos em laborat?rio atrav?s do equipamento E5071C ENA Network Analyzer. Por fim, realizaremos uma an?lise comparativa, mostrando o quanto a metasuperf?cie melhora a performance de uma antena de microfita atrav?s de uma an?lise dos diversos par?metros da antena, como: perda de retorno, ganho de pot?ncia, diretividade e imped?ncia de entrada. / This paper aims to present the influence of a metasurface, a special type of metamaterials, in the performace of microstrip antennas. The metasurface are artificial materials that are not found in a conventional manner in nature and do not have conventional electromagnetic characteristics such as refractive index and coefficient of permittivity and negative magnetic permeability which causes attractive electromagnetic effects for various applications, such as: improving the performance of a microstrip antenna as will be shown in this work. We started the work showing a brief history, definitions and electromagnetic properties of the antennas, microstrip antennas, metamaterials and metasuperf?cies. Next, we will design and manufacture a microstrip antenna with and without the use of a metasurface where we will simulate through HFSS Ansoft Designer software and test in the laboratory with the E5071C ENA Network Analyzer. Finally, we will perform a comparative analysis, showing how the metasurface improves the performance of a microstrip antenna by analysis of the various parameters antenna, such as: return loss, power gain, directivity and input impedance.
94

Effect of Chaos and ComplexWave Pattern Formation in Multiple Physical Systems: Relativistic Quantum Tunneling, Optical Meta-materials, and Co-evolutionary Game Theory

January 2012 (has links)
abstract: What can classical chaos do to quantum systems is a fundamental issue highly relevant to a number of branches in physics. The field of quantum chaos has been active for three decades, where the focus was on non-relativistic quantumsystems described by the Schr¨odinger equation. By developing an efficient method to solve the Dirac equation in the setting where relativistic particles can tunnel between two symmetric cavities through a potential barrier, chaotic cavities are found to suppress the spread in the tunneling rate. Tunneling rate for any given energy assumes a wide range that increases with the energy for integrable classical dynamics. However, for chaotic underlying dynamics, the spread is greatly reduced. A remarkable feature, which is a consequence of Klein tunneling, arise only in relativistc quantum systems that substantial tunneling exists even for particle energy approaching zero. Similar results are found in graphene tunneling devices, implying high relevance of relativistic quantum chaos to the development of such devices. Wave propagation through random media occurs in many physical systems, where interesting phenomena such as branched, fracal-like wave patterns can arise. The generic origin of these wave structures is currently a matter of active debate. It is of fundamental interest to develop a minimal, paradigmaticmodel that can generate robust branched wave structures. In so doing, a general observation in all situations where branched structures emerge is non-Gaussian statistics of wave intensity with an algebraic tail in the probability density function. Thus, a universal algebraic wave-intensity distribution becomes the criterion for the validity of any minimal model of branched wave patterns. Coexistence of competing species in spatially extended ecosystems is key to biodiversity in nature. Understanding the dynamical mechanisms of coexistence is a fundamental problem of continuous interest not only in evolutionary biology but also in nonlinear science. A continuous model is proposed for cyclically competing species and the effect of the interplay between the interaction range and mobility on coexistence is investigated. A transition from coexistence to extinction is uncovered with a non-monotonic behavior in the coexistence probability and switches between spiral and plane-wave patterns arise. Strong mobility can either promote or hamper coexistence, while absent in lattice-based models, can be explained in terms of nonlinear partial differential equations. / Dissertation/Thesis / Ph.D. Electrical Engineering 2012
95

Fabrication, structural and optical study of self-assembled hyperbolic metamaterial / Fabrication et étude structurale et optique de métamatériaux hyperboliques auto-assemblés

Wang, Xuan 29 September 2017 (has links)
Des propriétés optiques inédites sont prédites si des nanorésonateurs optiques sont organisés dans un matériau, ce qui peut être réalisé par l’auto-assemblage de nanoparticules plasmoniques synthétisées chimiquement. Dans ce travail de doctorat, nous utilisons des structures ordonnées de copolymères à blocs pour organiser des nanoparticules plasmoniques. Nous étudions le lien entre la structure des nanocomposites en films minces, et en particulier la nature, la densité et l’organisation des nanoparticules, et leurs propriétés optiques. Pour cela, nous avons tout d’abord produit des phases lamellaires de copolymères diblocs poly(styrène)-block-poly(2-vinylpyridine) (PS-b-P2VP) en films minces d’épaisseur (100nm-700nm) et de période lamellaire (17nm-70nm) contrôlées, et dont l’alignement et l’homogénéité sont optimisés. Nous avons développé une synthèse in situ, au sein de ces films lamellaires, qui permet de produire de façon contrôlée et reproductible, des nanoparticules plasmoniques de diamètre 7-10nm sélectivement dans les domaines P2VP. Nous avons montré que la taille et la forme des particules d’or formées in situ peuvent être modifiées en jouant sur le solvant et le réducteur chimique mis en jeu. Nous avons étudié en détail la structure des nanocomposites formulés, ce qui est en particulier nécessaire à la bonne exploitation des données d’ellipsométrie spectroscopique afin de déterminer les réponses optiques. La structure des échantillons a été étudiée par différentes méthodes de microscopie (électronique en transmission ou à balayage, à force atomique), ainsi que de la diffusion des rayons X. Nous avons utilisé une microbalance à Quartz pour étudier la quantité d’or introduite dans les matrices lamellaires de manière « cinétique » au fil de son augmentation progressive. La quantité d’or atteint des valeurs de 40 % en volume. Les propriétés optiques des films nanocomposites sont déterminées par ellipsométrie spectroscopique à angle variable et analysées à l’aide de modèles de milieux effectifs. Les films sont homogènes et anisotropes uniaxes, et on peut définir leur tenseur de permittivité diélectrique avec une composante ordinaire εo (parallèle au substrat) et une composante extraordinaire εe (perpendiculaire au substrat). L’analyse permet de montrer que les deux composantes εo and εe présentent une résonance proche de la longueur d’onde =540nm, avec une amplitude très supérieure pour εo. Lorsque la quantité d’or dans la structure lamellaire est suffisante, εo devient négatif au voisinage de la résonance et le matériau atteint le régime appelé hyperbolique, ce qui constitue un jalon essentiel pour le développement de matériaux pour des applications en imagerie hyper-résolue. / Novel optical properties in the visible range are foreseen when organizing nanoresonators, which can be performed by the self-assembly of plasmonic nanoparticles prepared by wet chemistry. In this project, we use templating block copolymers structures to organize plasmonic particles. Our goal is to relate the structure of the prepared nanocomposites thin films, and in particular the nature, density and spatial organization of the nanoparticles, with their optical index.For this purpose, we first fabricate lamellar superlattices of diblock copolymers (poly(styrene)-block-poly(2-vinylpyridine) of controlled thickness (100nm-700nm), controlled lamellar period size(17 nm-70 nm) and optimized alignment and homogeneity. Following the fabrication of the multilayer templates, an in situ and reproducible synthesis of metallic nanoparticles was developed in order to generate nanocomposites selectively inside the P2VP layers. The size of Au nanoparticles can be well controlled around 7-10 nm. We also found that the reduction process could influence the shape (sphere, triangle or cylinder) and size by using different solvents or reducing agents. Because the extraction of accurate optical responses from the spectroscopic ellipsometry data, which will come in the last part, critically relies on the precise knowledge of the sample structure. We have used several experimental techniques to access a precise description of the produced materials. In particular, we used a Quartz Crystal Microbalance as a measurement tool to ‘kinetically’ study the volume fraction of Au loading. We find that the amount of gold in the composite layers can be varied up to typically 40 volume%. The optical properties of the nanocomposite films are determined by variable angle spectroscopic ellipsometry and analyzed by appropriately developed effective medium models. The films are structurally uniaxial and homogeneous, and we can define their dielectric permittivity tensor with the ordinary (parallel to the substrate) and extraordinary (normal to the substrate) components. The analysis of the lamellar structures allows the extraction of the components εo and εe, both presenting a resonance close to =540nm, with a significantly stronger amplitude for εo. When the gold load is high enough and the couplings between particles are strong enough, the values of εo become negative close to the resonance, and the material reaches the so-called hyperbolic regime, which constitutes a step towards applications in hyper-resolution imaging.
96

Conception et réalisation d'un isolateur coplanaire en bande X pour des applications télécoms / Design and fabrication of a X-band coplanar isolator for telecommunication applications

Kirouane, Souad 05 May 2010 (has links)
La minimisation des circuits et la montée en fréquence constituent deux enjeux importants des systèmes de communication du futur. Cela nécessite un haut degré d'intégration, des performances plus élevées à coût réduit. Ce travail a pour objectif la conception et la réalisation de nouveaux isolateurs réalisés sur ligne coplanaire asymétrique à base de deux types de matériaux ferrite : hexaferrite de baryum (BaM) et grenat d’yttrium et de fer (YIG). La première étude, présentée sur une structure coplanaire à couche de BaM, a été effectuée pour montrer la faisabilité d’un isolateur à déplacement de champ dans la bande 40-50 GHz. La seconde a utilisé le YIG saturé pour des applications autour de 10 GHz. La nouvelle structure d’isolateur utilise le phénomène physique de déplacement de champ lorsqu’elle est polarisée par un champmagnétique continu. Elle est constituée d’une ligne coplanaire asymétrique gravée sur une couche ou un substrat magnétique et d’un demi-plan de masse arrière. Plusieurs séries de prototypes ont été fabriquées puis caractérisées à partir d’un banc de mesure hyperfréquence composé d’un testeur sous pointes à trois accès et d’un analyseur vectoriel de réseaux. Les résultats expérimentaux sont très encourageants car nous obtenons des pertes d’insertion faibles, dans le meilleur des cas inférieures à 1 dB et une isolation de plus de 16 dB. / The minimization of circuits and the increasing frequency are two important issues of future communication systems. That requires a high degree of integration, higher performance at reduced cost. This work aims to design and implementation of new isolators on coplanar line based on two types of ferrite materials: barium hexaferrite (BaM) and garnet and yttrium iron (YIG). The first study presented on a planar layer of BaM leads to the feasibility of the isolator of field displacement in the 40-50 GHz band. The second one concerns the use of saturated YIG for applications around 10 GHz. The magnetic field displacement phenomenon appears when the magnetic substrate is polarized by a D.C. magnetic field. The new isolator structure is made from an asymmetric coplanar line put on a layer or magnetic substrate with a half ground plane placed under this substrate. Several sets of prototypes are fabricated and characterized from a measurement bench which is composed by a microwave prober and a vector network analyzer. The experimental results are very promising because low insertion loss (less than 1 dB) and isolation (over 16 dB) have been obtained
97

Conception robuste d'actionneurs électromécaniques distribués pour le contrôle vibroacoustique de structures / Robust design of electromechanical distriuted systems for vibroacoustic structural control

Matten, Gael 08 July 2016 (has links)
Cette thèse concerne le développement d’outils de conception nécessaires à la réalisation de matériaux composites hybrides intégrant des patchs piézoélectriques shuntés électriquement par des circuits à capacité négative. L’impact des incertitudes sur les performances de ces systèmes hybrides innovants est à ce jour inconnu ou mal maîtrisé, ce qui peut compromettre leur fiabilité et nuire à leur applicabilité industrielle. La première contribution du travail de thèse a ainsi porté sur le développement et la caractérisation d’un circuit de shunt numérique adapté à un contrôle adaptatif pour une structure équipée d’un grand nombre de patchs. Les étapes de dimensionnement et de conception électronique du dispositif sont présentées et ont conduit à un prototype qui a montré expérimentalement sa capacité à générer un shunt de type capacité négative. La deuxième contribution du travail de thèse porte sur l’analyse de la robustesse de ces dispositifs en considérant le système dans sa globalité, depuis les paramètres géométriques (dimensions) ou matériaux jusqu’aux paramètres électriques. Une analyse des paramètres les plus influents est proposée et conduit à une mise en évidence des plages d’incertitudes tolérables pour une efficacité donnée. Enfin l’association des dispositifs considérés en un réseau distribué permet d’envisager une meilleure réduction des vibrations ou ondes acoustiques par un accroissement notamment de la largeur de bande fréquentielle dans laquelle le système est efficace. Le circuit numérique développé dans la thèse permet d’envisager cette extension au caractère distribué par sa miniaturisation, son adaptabilité et son intégrabilité. La dernière contribution du travail de thèse porte donc sur des perspectives d’extension du travail développé à un système distribué pour la génération d’une inter face active intégrée à la structure. / This thesis deals with the development of design tools needed for the realization of hybridcomposite materials incorporating piezoelectric patches electrically shunted by negativecapacitance circuits. The impact of uncertainty on the performance of these innovative hybridsystems is yet unknown or poorly controlled, which can compromise their reliability and harmtheir industrial applicability. The first thesis contribution has focused on the development andcharacterization of a digital shunt circuit adapted to an adaptive control for a structureequipped with a large number of patches. The design steps and electronic device design arepresented and led to a prototype that has shown experimentally its ability to implement anegative capacitance shunt. The second contribution of the thesis is the analysis of therobustness of these devices by considering the whole system, from geometric to materialsparameters, including the electrical parameters. An analysis of the most significantparameters is proposed and has highlighted the tolerable uncertainty ranges for a givenefficiency. Finally, the combination of the developed digital devices inside a distributednetwork provides a better reduction of acoustic waves or vibrations by increasing theefficiency bandwidth. The use of the developed digital circuit in such distributed systems hasbeen made possible by its miniaturization, adaptability and integrability. The last contributionof the thesis therefore focuses on prospects in fully integrated active interfaces.
98

The directivity of a compact antenna: an unforgettable figure of merit

Ziolkowski, Richard W. 11 October 2017 (has links)
When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.
99

Transition métamatériau / sol réel pour radar HF à onde de surface / Transition between a Metamaterial and the Soil for High Frequency Surface Wave Radar

Bourey, Nicolas 21 November 2014 (has links)
Depuis plusieurs années, des recherches sont conduites à l'ONERA, sur les radars " transhorizon " et notamment sur le radar de surveillance côtière à onde de surface (ROS). En vue d'augmenter les performances de ce radar, il est nécessaire d'améliorer son rayonnement en onde de surface. Lors de précédents travaux réalisés à l'ONERA et à l'UPMC, il a été proposé d'utiliser un métamatériau pour lancer, vers la surface de la mer, une onde confinée, ce qui est impossible avec un matériau à permittivité positive. Le métamatériau devra être placé sur le sol, devant les antennes d'émission du radar, ce qui permettra d'augmenter leur rayonnement vers la surface, sans pour autant modifier significativement l'architecture du système. Mais l'ajout du métamatériau crée une rupture d'impédance entre le métamatériau et le sol. L'objectif de ces travaux de thèse est de répondre à deux questions principales. La rupture d'impédance existant entre le métamatériau et le sol va-t-elle diffracter l'onde de surface créée sur celui-ci ? L'augmentation du niveau de champ électrique, à la surface du métamatériau, va-t-elle se conserver lors de la propagation sur la mer ? / For many years, researches « on over the horizon radar » are investigated, especially on the High Frequency Surface Wave Radar (HFSWR), which is dedicated to the maritime surveillance. To increase the efficiency of the HFSWR we deal with the part of the electromagnetic field radiated at low elevation angle. In a previous work conducted at ONERA and UPMC, it has been suggested to use a metamaterial to launch, at the interface between air and ground a confined wave, which can not exist with a soil with positive permittivity. The metamaterial is placed on the interface in the vicinity of the transmitting antennas to allow the propagation of a strong surface wave without modifying significantly the architecture of the system. But, the inclusion of this metamaterial creates a quite high discontinuity in permittivity. The principal aim of this research work is to answer two main questions. The discontinuity of permittivity between the metamaterial and the soil, is it going to diffract the surface wave create over the metamaterial? The improvement of the electric field level at low elevation angle metamaterial, is it going to keep throughout the propagation on the sea?
100

Metamaterial stepped impedance resonator filters for wireless communication systems

Karimian, Shokrollah January 2011 (has links)
This thesis introduces, for the first time, Stepped Impedance Resonator (SIR) bandpass filters (BPF) based on Composite Right/Left-Handed (CRLH) transmission lines. In other words, a novel approach in design of BPFs for RF and microwave applications is successfully proposed and examined, which can serve both miniaturisation and performance enhancement purposes. In conducting this research, design, development and optimisation procedures and techniques for the proposed BPFs have been presented. Theoretical, numerical and experimental results have confirmed that these filters are capable of significantly reducing the size while maintaining the integrity of the filter performance; and in some cases, extensively enhancing the performance.Two λg/4-type CRLH SIRs are designed and characterised based on the available equations. ADS lumped-element equivalent circuit model and HFSS full-wave electromagnetic simulation, and measurement results prove that both CRLH SIRs surpassed their RH counterparts, in terms of both size and performance. Indeed, comparison of the first CRLH SIR with its RH counterpart revealed a 35% size (length) reduction. The second CRLH SIR design is measured to be 66% smaller than its RH counterpart and 14% smaller than the initial CRLH SIR. In addition, simulation and measurement results reveal that an intelligently designed CRLH SIR shows a better quality factor Q and input impedance |Zin| response, and provides higher design flexibility. Phase unwrapping and energy (current) flow analysis have been used to prove left-handedness of the CRLH SIRs. The concept is extended to propose multi-section (λg/2-type and tri-section SIRs) and tunable CRLH SIRs. Numerical analysis and obtained results show that the λg/2-type CRLH SIR benefits from a 45% size (length) reduction compared to its RH counterpart, and a better |Zin| response. The results obtained from the tri-section CRLH SIR (TSSIR), clearly show that the TSSIR is capable of relocating (and minimising) the multiple spurious resonance frequencies, while maintaining the same fundamental frequency f0. As such, no spurious frequency is observed before 8 GHz. Also, measurements indicated that the CRLH TSSIR is not only 30% smaller in length compared to its RH counterpart, it was even 28% smaller than a two-section RH SIR resonating at the same frequency of 2.5 GHz. In addition, the tuning capability of the ferrite CRLH SIR is illustrated when the operating frequency of the resonator is tuned from 5.1 GHz to 5.4 GHz, and 5.65 GHz for H0 = 2000, 2250, and 2500 Oe, respectively.These SIRs are then combined and configured to form two main categories of CRLH SIR bandpass filters: PCB filters based on RT Duroid and MMIC filters based on GaAs. In both filters, the homogeneity condition has been satisfied by ensuring that the longest length is much less than λg (in this case l = λg/12) for PCB-based filters and l = λg/14 for MMIC filters at the centre frequency of the filters. The first PCB-based CRLH SIR filter, which has been designed to operate at 2.75 GHz, is measured 24mm × 28mm. HFSS 3-D full-wave simulations and measurement results of this filter reveal that, with an insertion loss of -2.6dB and return loss of -21.5dB, the filter not only has a very good selectivity, but also is extremely efficient in extending the free-spurious stop-band, pushing the first spurious response to around 11 GHz (about 4×f0). The second PCB-based CRLH SIR filter has much smaller size, measuring overall filter dimensions of 6mm × 5.14mm. This filter also benefits from a smaller resonator size, improved overall coupling and a more controllable circuit. Theory, full-wave simulation and measurement results demonstrate that, with an insertion loss of -1dB and return loss of -34dB, the miniaturised CRLH SIR filter proves very successful as it was about 80% smaller in size compared to its RH counterpart with the same centre frequency, while maintaining the integrity of the filter performance. Moreover, the miniaturised CRLH SIR BPF is significantly more controllable in its dimensions and response due to the fact that more elementary parameters are available in the CRLH configuration.The MMIC CRLH SIR bandpass filters are then proposed with an emphasis on further size reduction with maintenance (or enhancement) of their transmission responses. As such, two classes of MMIC filters were designed: the first one is very small measuring 3.2mm × 3.4mm, with an insertion loss of -5.3dB at the centre frequency 3.1 GHz. The filter also shows good attenuation both before and after the passband with its first spurious frequency occurring at 13.52 GHz (i.e. > 4×f0). The second set of MMIC filters employed multilayer topology to reduce the filter size. It has been clearly shown that with an intelligent design, the size (dimension) limitations of the PCB-based filters have been overcome by using the MMIC technology, resulting in filters with significantly reduced sizes - design I: 1.32mm×3.35mm, and design II: 1.4mm × 1.5mm. It has also been observed that MMIC structures are generally exposed to inevitable losses, though steps can be taken to reduce such losses.

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