Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Keywords: Coupled resonator filters, Co-axial line resonators, Basic Coupling Design, Co-axial resonator filter The study of the basic dynamics of filters, with the emphasis on coupled resonator filters, is presented. Special attention is paid to the synthesis of doubly terminated coupling matrices using the Darlington method. Due to restrictions placed on the filter by the equivalent circuit used, a coupling matrix reduction is applied to the resulting coupling matrix. An investigation is performed on A/2 co-axial line resonators, with the emphasis on rectangular co-axial line resonators with a round center conductor. The basic definition of the coupling coefficient is revisited and it is calculated using the method based on Bethe's theory and Cohn's experimental work. A 4th-order co-axial resonator filter operating at 3 GHz is designed using the theory outlined in this thesis. The measured response is in good agreement with the theory in terms of the center frequency, but disagree in terms of the coupling coefficient, bandwidth and Q-factor. The reasons for this, as well as suggestions for improving the accuracy of the parameters mentioned, are given. / AFRIKAANSE OPSOMMING: Sleutelwoorde: Gekoppelde resoneerder filters, Ko-aksiale lyn resoneerders, Basiese Koppeling Ontwerp, Ko-aksiale resoneerder filter Die studie van die basies dinamika van filters, met die klem op gekoppelde resoneerder filters, is voorgelê. Spesiale aandag is gegee aan die sintese van dubbelbelaste koppel matrikse met die gebruik van die Darlington metode. As gevolg van die beperkings wat op die filter geplaas word deur die gebruik van die ekwivalent stroombaan, word 'n koppel matriks vermindering gebruik. 'n Ondersoek is gedoen op A/2 ko-aksiale lyn resoneerders, met die klem op reghoekige ko-aksiale lyn resoneerders met 'n ronde binnegeleier. Die basiese definisie van die koppel koëffisiënt is hersien en dit is bereken met die gebruik van die metode wat baseer is op Bethe se teorie en Cohn se experimentele werk. 'n 4de-orde ko-aksiale resoneerder filter wat opereer by 3 GHz is ontwerp met die gebruik van die teorie wat in hierdie tesis gaskets word. Die gemete weergawe is in goeie ooreenkoms met die teorie in terme van die senter frekwensie, maar verskil in terme van die koppel koëffisiënt, bandwydte en Q-faktor. Die rede hiervoor, as ook voorstelle vir die verbetering van die akkuraatheid van die parameters wat genoem is, IS gegee.

3D printable materials for RF devices need improvement in order to satisfy the demand for higher frequency and lower loss performance. Characterization of materials that have shown improvements of conductor conductivity have been performed. By using a laser machining technique the loss of a 3D printed 2.45 GHz microstrip Square Open Loop Resonator (SOLR) bandpass filter has been shown to improve by 2.1dB, along with an increase in bandwidth from 10% to 12.7% when compared to a SOLR filter that has not been laser machined. Both laser machined and microwaved silver inks have been mapped for conductivity using a Near Field Microwave Microscope (NFMM) and have shown improvement of conductivity compared to inks that have been cured using standard methods.

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.

Orientador: Hugo Enrique Hernandez-Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T16:04:15Z (GMT). No. of bitstreams: 1 LlerenaCastro_OscarEnrique_M.pdf: 5834212 bytes, checksum: f007c788f1123ca923e5f860548252f0 (MD5) Previous issue date: 2014 / Resumo: Os filtros passa-faixa feitos com ressonadores coaxiais cerâmicos são um tipo de tecnologia de filtro que fornece características de alta performance como a alta seletividade, ótimo desempenho em aplicações de alta potência, excelente rejeição, baixa perda de inserção na banda passante, etc. , e dado que os ressonadores são feitos de materiais de alta constante dielétrica consideravelmente, consequentemente, todas as características elétricas mencionadas anteriormente são compactadas em uma estrutura protegida o qual faz que este tipo de filtros sejam adequados para aplicações onde precisam-se de dispositivos de tamanho pequeno. A parte mais difícil no momento de projetar este tipo de filtros é encontrar as dimensões certas da estrutura, sejam as alturas dos ressonadores ou as dimensões da estrutura dos capacitores de acoplamento. Esta tese presenta um estudo feito neste tipo de filtro e propõe um procedimento analítico-empírico com formulas para projeção para facilitar a construção do arranjo de ressonadores e a estrutura dos capacitores de acoplamento. Este procedimento pode ser extrapolado para filtros passa-faixa com um maior número de ressonadores. As formulas de projeção permitem uma transição fácil do modelo circuital ao modelo eletromagnético do filtro. Isto deve-se com as formulas é fácil calcular os comprimentos dos ressonadores e os valores das capacitâncias requeridas para acoplar corretamente os ressonadores. A comparação entre as simulações no modelo circuital e o entorno eletromagnético mostram que as formulas de projeção propostas são uma ótima primeira aproximação para a projeção deste filtro / Abstract: Bandpass filters made with ceramic coaxial resonators are a kind of filter technology that provides high performance features like high selectivity, high power handling, excellent rejection, low passband insertion loss, etc. and given that the resonators are made of with materials of high dielectric constant it considerably reduces their size, consequently, all the electric characteristics mentioned before are "compacted" in a small shielded structure which make these filters suitable for applications where small sized devices are a necessity. The most difficult task when projecting this kind of filters is to find the correct dimensions of the structure, either the length of the resonators or the dimensions of the coupling capacitors structure. This thesis presents a study on this type of filter and propose an analytical-empirical procedure with design formulas to facilitate construction of the resonators array and the coupling capacitors structure. This procedure can be extrapolated to bandpass filters with a greater number of resonators. The design formulas allow an easy transition from the circuital model to the electromagnetic model of the filter. This is because they easily allow to compute the length of the resonators and the value of the capacitances required for a correctly resonators coupling. The comparison between the simulations in the circuital and the electromagnetic environment show that the proposed design formulas are a good first approximation for this filter design / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

<p>Filtri predstavljaju nezaobilazan deo svakog mikrotalasnog uređaja. Skorašnji veoma brz razvoj bežičnih sistema pred mikrotalasne filtre postavlja nove zahteve kao što su visoke performanse, kompaktnost i rad na više proizvoljno odabranih učestanosti koje se mogu nezavisno kontrolisati.<br />Naučni doprinos ove doktorske disertacije predstavlja pet novih konfiguracija mikrotalasnih multi-band filtara koji su realizovani u mikrostrip arhitekturi. Od toga tri konfiguracije predstavljaju dual-band filtre, a preostale dve konfiguracije tri-band filtre. Filtri su realizovani korišćenjem fraktalnih krivih i/ili savijenih &lambda;/4 rezonatora, i to u klasičnoj tehnologiji štampanih ploča i u višeslojnoj tehnologiji nisko-temperaturne zajedno pečene keramike.<br />Detaljno je analiziran i opisan način rada predloženih filtara. Filtri su fabrikovani, a njihove performanse izmerene i upoređene sa drugim rezultatima dostupnim u literaturi. Pokazano je da predložene filtre karakteriše mogućnost nezavisne kontrole propusnih opsega što je iskorišćeno za realizaciju dual-band filtara koji rade na WLAN 2.4/3.5 GHz opsezima i tri-band filtara koji rade na WLAN 2.4/3.5/5.2 GHz opsezima. Štaviše, predložene tri-band strukture predstavljaju najmanje tri-band filtre do danas predložene u literaturi.</p> / <p>Filters are indispensable components in any microwave device. Recent rapid development of wireless systems posed new demands to microwave filters, such as high performance, compact size and the ability to simultaneously operate on several independently selected frequencies.<br />Scientific contribution of this dissertation are five novel microwave multi-band filters realized in microstrip architecture. Out of the five, three configurations are dual-band filters, while the remaining two are tri-band filters. Filters are designed using fractal curves and/or folded &lambda;/4 resonators, in the conventional printed circuits technology or in low-temperature cofired ceramics technology.<br />Operating principles of the proposed filters have been analyzed and explained in detail. Their performances have been measured and compared to other recently published results. It has been shown that the proposed filters allow independent control of the passbands. This has been used to design dual-band filters operating at WLAN frequencies of 2.4/3.5 GHz and tri-band filters operating at WLAN frequencies of 2.4/3.5/5.2 GHz. Moreover, the proposed tri-band filters are the most compact tri-band filters published so far.</p>

La conception de filtres hautes fréquences requiert l’optimisation des paramètres physiques du filtre afin d’obtenir une réponse en fréquence qui remplit les conditions imposées par le gabarit de fréquence. Cette optimisation dépend de simulations électromagnétiques. La résolution de ces équations aux dérivées partielles étant très couteuse en temps de calcul, nous proposons de développer des modèles pour le filtre qui permettent de réduire le nombre de simulations EM nécessaires au réglage du filtre. Le but recherché est d’incorporer ces modèles dans une méthode de conception assistée par ordinateur. Dans cette thèse, je propose différentes approches pour la modélisation du filtre. La première approche utilise la matrice de couplage du filtre, qu’elle décrit en fonction des paramètres physiques. La deuxième approche modélise les paramètres S en fonction de ces mêmes paramètres. Dans la première méthode, on se concentre essentiellement sur l’extraction de la matrice de couplage physique. On introduit une technique pour estimer la matrice de sensibilité (le Jacobien) qui lie les paramètres physiques aux paramètres de couplage. Cette estimation utilise les sensibilités adjointes des paramètres. L’utilisation de cette information réduit drastiquement le nombre de simulations EM et donc le temps de calcul global. Une deuxième approche utilise le concept de méta-modèle. L’idée maitresse de cette approche est que l’évaluation de ce modèle est numériquement beaucoup plus avantageuse que celle des simulations EM. Les méthodes développées sont tour à tour appliquées à la conception de filtres complexes qui sont réalisés en technologie microstrip / The design of microwave bandpass filter generally requires optimization or fine-tuning of the physical design parameters in order to meet the electrical specifications given by a frequency template. In this thesis we develop models to assist the designer in the time-efficient physical design of the distributed element microwave filters. The aim is to incorporate these models in different CAD methods. By a time-efficient design, we mean a design that requires a low number of EM simulations. The EM-simulations typically represent the most time-consuming step during the optimization process. We propose different modeling approaches for the frequency response behavior of the filter. The first approach models the coupling matrix as a function of the physical design parameters and the second approach models the scattering parameters, again as a function of the physical parameters. In the first part we focus on the extraction of the coupling matrix. We introduce a novel CAT technique based on an efficient estimation of the Jacobian of the function relating the design parameters to the coupling parameters. The estimation of the Jacobian uses adjoint sensitivity analysis, which drastically reduces the number of required EM-simulations. In the second part of the thesis we propose an alternative modeling approach which is based on the concept of a metamodel. The idea is that the metamodel is numerically much cheaper to evaluate than the original simulation model while keeping an acceptable accuracy. We apply these methods to several state of-the-art microstrip bandpass filters

The integration of high-quality (Q)-factor 3-D filters with highly efficient antennas is addressed in this dissertation. Integration of filters and antennas into inseparable units eliminates the transitions between the otherwise separate structures resulting in more compact and efficient systems. The compact, highly efficient integrated 3-D filter/antenna systems, enabled by the techniques developed herein, allow for the realization of integrated RF front ends with significantly- reduced form factors. Integration of cavity filters with slot antennas in a single planar substrate is first demonstrated. Due to the high Q factor of cavity resonators, the efficiency of the integrated filter/antenna system is found to be the same as that of a reference filter with the same filtering characteristics. This means a near 100% efficient slot antenna is achieved within this integrated filter/antenna system. To further reduce the footprint of the integrated systems, vertically integrated filter/antenna systems are developed. We then demonstrate the integration of cavity filters with aperture antenna structures which enable larger bandwidths compared with slot antennas. The enhanced bandwidths are made possible through the excitation and radiation of surface waves. To obtain omnidirectional radiation patterns , we integrate cavity filters with monopole antennas. Finally, the integration of filters with patch antennas is addressed. Unlike the other filter/antenna integration examples presented, in which the antenna is utilized as an equivalent load, the patch antenna provides an additional pole in the filtering function. The presented techniques in this dissertation can be applied for filter/antenna integration in all microwave, and millimeter-wave frequency regions

It is often necessary to operate a number of radio communication channels from a single control room without time-sharing between the various channels. Here it is necessary to operate a number of transmitters and receivers simultaneously from the same base station or mobile unit without interference. The best method to achieve this has been found in the use of filters inserted in the transmission line between the antenna and the transmitter(s) on one hand and the receiver(s) on the other hand. The basic unit employed in the design of microwave filters is usually a cavity resonator of which the most important factors are the Q, insertion loss and resonant frequency. However, a problem which frequently arises with cavity resonators is the accurate determination of these resonant characteristics complicated by the presence of coupling port, materials and various design and geometrical deviations. Such cavities have been investigated in several cases and the results have been generalised, but this investigation has been conducted to examine thoroughly most of the problems being met in present practice. Design and development of some common resonant structures are considered. Emphasis is placed on solutions found to special problems especially regarding complicated boundary conditions. Furthermore, investigation includes methods for optimising resonant parameters such as insertion loss and Q, trading of insertion loss with coupled cavity selectivity, frequency tuning and compensation for frequency variations due to wide ranges of operating temperatures. By comparing Q values obtained in practice with theoretical values, it has been possible to establish an appropriate Q loss budget to as to facilitate accurate prediction of coupled cavity unloaded Q. A satisfactory agreement between theory and practice has been obtained. By application of the results of theoretical analysis and experiment, it is shown that microwave filters can be designed to have a desired insertion loss and off-band attenuation slope. Steps leading to designs of any number of cascaded cavities in a two-port network and, subsequently, multi-port networks are discussed in detail.

The electromagnetic spectrum is becoming increasingly congested due to the rapid development of wireless and mobile communication in recent decades. New, compact and efficient passband filters with multi-functions and good performance are highly demanded in current and future wireless systems. This has also driven considerable technological advances in reconfigurable/tunable filter and filtering antenna designs. In light of this scenario, the objectives of this thesis are to design, fabricate and measure efficient, compact, multi-standard, and reconfigurable/tunable microstrip resonator filters and study the integration of the resonators with patch antennas. As a passive design, a compact dual-band filter is implemented to cover 2.5 to 2.6 GHz and 3.4 to 3.7 GHz for 4G and 5G, respectively. Another design is also presented with the advantages of a wide passband of more than 1 GHz. Conversely, new and compact reconfigurable filters are designed using varactor and PIN diodes for 4G and 5G. The proposed filters are tunable in the range from 2.5 to 3.8 GHz. The bandwidth is adjustable between 40 and 140 MHz with return losses between 17 to 30 dB and insertion loss of around 1 dB. Also, the thesis investigates the design of cascaded and differentially-fed filtering antenna structures. The cascaded designs operate at 2.4 and 6.5 GHz and have a relatively wide-band bandwidth of more than 1.2 GHz and a fractional bandwidth of more than 40%. For the differentially-fed structures, good performance is achieved at the 3.5 GHz with a high realized gain of more than 7.5 dBi is observed. / European Union Horizon 2020 Research and Innovation Programme (Marie Skłodowska-Curie Actions) under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Yes / This study presents an original asymmetric stepped-impedance resonator filter combined with meander coupled-line structures and enabling the realisation of finite transmission zeros (TZs) and the implementation of multi-band bandpass filters. The meander coupled sections (MCSs) tune the TZs and resonant frequencies: with higher-order spurious frequencies cancelled by the TZs, a single wideband with wide stopband from 1.18 to 1.84 GHz is possible. Furthermore, by positioning the finite TZs between the high-order spurious frequencies and adjusting the coupling strength between resonators, a quint-wideband filter can be realised, with centre frequencies of 1.19, 4.29, 5.43, 6.97, 9.9 GHz and fractional bandwidths of 31.9, 15.4, 15.8, 4.3, 39.2%, respectively. More importantly, two filters with single/quad-wideband performance can be realised by tuning the parameters of the MCS, and therefore they can be designed separately by using only one original structure. The triple-wideband filter is realised with the help of the asymmetric parallel uncoupled microstrip section. These filter structures enjoy the advantage of single/multi-band versatility, structure reusability and simplicity. The good in-band and out-of-band performance, low loss and simple structure of the proposed single/tri/quint-wideband filters make them very promising for applications in future multi-standard wireless communication. / European Union's Horizon 2020 research and innovation programme under Grant agreement H2020-MSCA-ITN-2016 SECRET-722424.