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Marques, Anselmo Miguel Magalhães. "Frustrated multiband superconductors." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12174.
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Mestrado em FísicaMotivada pela recente descoberta de supercondutores baseados em ferro, com altas temperaturas críticas e possibilidade de coexistência de múltiplas bandas no nível de Fermi, esta dissertação pretende estudar as condições sob as quais se podem manifestar configurações frustradas nas fases supercondutoras, em função das variáveis temperatura e campo magnético externo aplicado. A Acão reciproca entre as interações atrativas/repulsivas interbandas e intrabandas e analisada, sendo apresentado o diagrama de fases de campo magnético vs. temperatura para um regime de acoplamento entre bandas fraco.
Motivated by the recent discovery of iron-based superconductors, having high critical temperatures and multiple bands crossing the Fermi level, this dissertation aims to study the conditions under which frustrated con gurations in the superconducting phases can be present, as a function of the variables temperature and externally applied magnetic eld. The interplay between interband and intraband attractive/ repulsive interactions is analysed, with the magnetic eld vs. temperature phase diagram being presented for the weakly interband coupling regime.
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Corrêa, Lucas Eduardo. "Investigação de supercondutividade em boreto do sistema Ta-Zr-B." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/97/97135/tde-03122018-184821/.
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Em trabalhos anteriores realizados em síntese e caracterização cristalográfica, a existência de uma nova fase de estequiometria Ta1-xHfxB (com x variando no intervalo entre 0,05 e 0,4) que cristaliza no protótipo FeB foi descoberta. Este ternário cristaliza num protótipo diferente do protótipo CrB aceito no binário TaB. Na verdade, essa substituição é capaz de gerar uma mudança significativa na estrutura cristalina de TaB, a qual sofre uma distorção e modifica o protótipo CrB para FeB. Além desta mudança estrutural os compostos de composição global Ta1-xHfxB apresentam supercondutividade com temperatura crítica supercondutora acima do binário TaB (Tc ~ 4,0 K). Foi observado que a supercondutividade otimizada na composição Ta0,7Hf0,3B com Tc ~ 6,7 K na qual medidas de calor específico revelam forte assinatura de manifestação multibanda neste novo composto. Motivados por esta descoberta, neste trabalho são investigadas a possiblidade desta transformação estrutural bem como o seu impacto nas propriedades supercondutoras em ligas de composição global Ta1-xZrxB, devido à similaridade eletrônica entre Zr e Hf na tabela periódica. De fato, resultados publicados a respeito da transformação cristalográfica com a substituição de Ta por Zr revelam o mesmo comportamento observado nas ligas produzidas com Hf e este trabalho revela que os compostos Ta1-xZrxB também são supercondutores. A composição com a maior temperatura crítica é Ta0,8Zr0,2Be tem uma temperatura de transição aproximadamente 7,8 K. Entretanto, esse composto tem evidencia de um supercondutor não convencional. Assim, este trabalho revela a existência de supercondutividade não convencional em ligas do sistema ternário Ta-Zr-B revelados por medidas de resistividade, magnetização e caracterização estrutural e microestrutural.In previous works carried out in synthesis and crystallographic characterization, the existence of a new Ta1-xHfxB stoichiometry phase (with x varying in the interval between 0.05 and 0.4) that crystallizes in the FeB prototype was discovered. This ternary crystallizes in a prototype different from the prototype CrB accepted in the TaB binary. In fact, this substitution is capable of generating a significant change in the crystalline structure of TaB, which undergoes distortion and modifies the CrB prototype for FeB. In addition to this structural change, the compounds of global composition Ta1-xHfxB present superconductivity with critical superconducting temperature above the TaB Tc ~ 4.0 K. It was observed that the superconductivity optimizes at Ta0,7Hf0,3B composition with Tc ~ 6.7 K in which specific heat measurements reveal a strong multiband manifestation signature in this new compound. Based on this finding, this work investigates the possibility of this structural transformation as well as its impact on the superconducting properties of alloys of global composition Ta1-xZrxB, due to the electronic similarity between Zr and Hf in the periodic table. In fact, published results on crystallographic transformation with the substitution of Ta by Zr reveal the same behavior observed in the alloys produced with Hf and this work reveals that the Ta1-xZrxB compounds are also superconducting. The composition with the highest critical temperature is Ta0,8Zr0,2Band has a transition temperature of about 7.8K. However, this compound has evidence of an unconventional superconductor. Thus, this work reveals the existence of unconventional superconductivity in alloys of the Ta-Zr-B ternary system revealed by resistivity, magnetization and structural and microstructural characterization measurements.
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Blaschke, Volker. "Multiband Cognitive Radio-Systeme." [S.l. : s.n.], 2008. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000009926.
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Saucier, Scott. "Multiband Analog-to-Digital Conversion." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/SaucierS2002.pdf.
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Abutarboush, Hattan F. "Fixed and reconfigurable multiband antennas." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/9037.
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With the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches.
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Maxwell, Michael. "Multiband observations of recurrent novae." Thesis, University of Central Lancashire, 2014. http://clok.uclan.ac.uk/10719/.
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Recurrent novae are binary systems which undergo outbursts due to a thermonuclear runaway on a timescale of decades. Two systems, U Scorpii and RS Ophiuchi, are the main focus of this thesis having gone into outburst in 2010 and 2006 respectively. Optical and near-IR spectroscopy of U Sco obtained with facilities including the Liverpool Telescope, the Very Large Telescope, and the Southern African Large Telescope, as well as ultra-violet and optical spectroscopy of RS Oph obtained with the Ultra-Violet and Optical Telescope, are presented here. Observations of U Sco obtained in outburst are used to determine the helium abundance of the ejecta, with observations in quiescence used to constrain the nature of the companion star and the accretion disc. Observations of RS Oph are used to produce lightcurves of the decline from maximum to the post-outburst minimum. Analysis of optical and near-IR spectra following the 2010 outburst of U Sco leads to the determination of the reddening and the helium abundance. The reddening is found to be E(B-V) = 0.17 ± 0.14, consistent with previous estimates. The helium abundance, N(He)/N(H), is determined to be 0.122 ± 0.018, lower than previous estimates and suggesting that the companion is not helium rich. The fitting of model stellar atmospheres to observations of U Sco in quiescence, obtained ∼18-30 months after the 2010 outburst, constrains the effective temperature of the companion and indicates that it is a cool F or hot G star. The accretion disc is found to be still in a state of development until at least ∼18 months after outburst, contrary to previous studies. The strength of the Heii 4686 ̊A line in quiescence is found to be consistent with a high mass white dwarf accreting solar-abundance material at a high rate. The He line strengths do not require an overabundance of helium, as has been previously suggested, consistent with the solar abundance of helium found in the ejecta of the 2010 outburst. UVOT observations of RS Oph following the 2006 outburst are used to produce B and u′ lightcurves of the decline to minimum. These lightcurves are used in con- junction with published V and B lightcurves to show the change in the colour of the system throughout the outburst. Spectra of RS Oph show the spectroscopic evolution during the initial decline, plateau, final decline, and post-outburst minimum phases. SALT spectra obtained during the late decline phase of the 2011 outburst of a third recurrent nova, T Pyxidis, are used to derive a helium abundance of N(He)/N(H)= 0.161 ± 0.013, approximately twice the solar value. Very strong [O iii] lines are also detected.
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Abunjaileh, Alaa Ibrahim. "Multimode and multiband microstrip antennas." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/759/.
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This thesis describes original work on the broadband and multiband matching of microstrip patch antennas. Microstrip patch antennas suffer from many constraints on their performance. One major restriction is their narrow impedance bandwidth. An effective method to resolve this is adding more resonators to the antenna structure to achieve multi-resonance and hence wider bandwidth. Structures such as circular, square and triangular patch antennas may support two orthogonal resonant modes or polarisations. This allows excitation of an additional resonance beside the fundamental. With the correct coupling between the resonant modes, the impedance bandwidth can be significantly increased. The equivalent circuit of such structures is similar to those used in microwave filter design. Using techniques normally employed in filter synthesis, the equivalent circuits can be generated, and aid in finding the couplings and dimensions of the specified antenna requirement. The bandwidth of circular microstrip patch antennas is significantly increased by exciting two modes on a single circular microstrip antenna, and four modes using two stacked circular microstrip patches. In this work, the designs are also extended into multimode antennas achieving multi-frequency operation.
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Blaschke, Volker [Verfasser]. "Multiband cognitive Radio-Systeme / Volker Blaschke." Karlsruhe : Inst. für Nachrichtentechnik, 2008. http://d-nb.info/998339180/34.
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Tzeng, Jack. "Multiband deblurring for fluid lens cameras." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3404214.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed June 10, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (leaves 96-100).
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Maassel, Michael. "A Metamaterial-Based Multiband Phase Shifter." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27095.
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A design methodology for a multi-band phase shifter using a metamaterial-based transmission line was developed. This method is different in that the loaded-line phase shifter has a phase shift of 90 degrees at the center frequencies of both bands instead of -90 degrees and -270 degrees. The method was validated using simulation and measured results.
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Pivit, Florian. "Multiband-Aperturantennen für Basisstationsanwendungen in rekonfigurierbaren Mobilfunksystemen /." Karlsruhe : IHE, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014885402&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Tejero, Alfageme Simón. "Resolution and accuracy in multiband radar sensors." Berlin Logos-Verl, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=3004797&prov=M&dok_var=1&dok_ext=htm.
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Corden, Ian Robert. "Efficient transmultiplexer algorithms multiband quadrature modulation schemes." Thesis, Staffordshire University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280562.
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Eckstein, Bernd. "Bandcounter: Counting bands of multiband chaotic attractors." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-28244.
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FIGUEIREDO, TIAGO NASCIMENTO DE. "BROADBAND RF POWER AMPLIFIERS FOR MULTIBAND TRANSCEPTORS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=22900@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEste trabalho descreve o desenvolvimento completo de um Amplificador de Potência de RF para Transceptores Multibanda. Em sua etapa inicial mostra um apanhado geral da teoria de todos os parâmetros relevantes para a medida de desempenho desses dispositivos, como potência, ganho e parâmetros de não linearidades. Em seguida são expostas as teorias básicas para o entendimento dos mecanismos para extração da máxima potência de um transistor, focando nos transistores de efeito de campo FET, incluindo a caracterização para regimes de alta potência. São apresentados os modos de operação de um amplificador de potência, focando nos chamados modos clássicos, dado que esses modos são convenientes para operação em banda larga. Para a correta operação de qualquer dispositivo que apresente ganho, a análise de estabilidade é apresentada com o procedimento de estabilização de transistores. A partir de todo o apanhado teórico, é desenvolvida uma metodologia de projeto de amplificadores de potência utilizando a ferramenta de simulação computacional Advanced Design System. Então, após toda a modelagem do amplificador, a construção e medidas são realizadas e boa concordância com a simulação foi obtida.
This work describes the full development of a RF Power Amplifier for Multiband Transceivers. In its initial stage shows an overview of the theory of all relevant parameters to measure the performance of these devices, like power, gain and nonlinearity parameters. Then it exposes the basic theories for the understanding of the mechanisms for extracting the maximum power of a transistor, focusing on field effect transistors FET, including characterization for regimes of high power. It presents the modes of operation of a power amplifier, focusing on so-called classical modes, since these modes are suitable for broadband operation. For proper operation of any device that presents gain, the stability analysis is presented with the stabilization procedure of transistors. From all theoretical basis, is developed a design methodology of power amplifiers using the computational simulation tool Advanced Design System. So after all the amp modeling, construction and measurements are performed and good agreement was obtained with the simulation.
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Badran, Salah Al-Din Ibrahim. "Efficient multiband algorithms for blind source separation." Thesis, De Montfort University, 2016. http://hdl.handle.net/2086/16089.
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The problem of blind separation refers to recovering original signals, called source signals, from the mixed signals, called observation signals, in a reverberant environment. The mixture is a function of a sequence of original speech signals mixed in a reverberant room. The objective is to separate mixed signals to obtain the original signals without degradation and without prior information of the features of the sources. The strategy used to achieve this objective is to use multiple bands that work at a lower rate, have less computational cost and a quicker convergence than the conventional scheme. Our motivation is the competitive results of unequal-passbands scheme applications, in terms of the convergence speed. The objective of this research is to improve unequal-passbands schemes by improving the speed of convergence and reducing the computational cost. The first proposed work is a novel maximally decimated unequal-passbands scheme. This scheme uses multiple bands that make it work at a reduced sampling rate, and low computational cost. An adaptation approach is derived with an adaptation step that improved the convergence speed. The performance of the proposed scheme was measured in different ways. First, the mean square errors of various bands are measured and the results are compared to a maximally decimated equal-passbands scheme, which is currently the best performing method. The results show that the proposed scheme has a faster convergence rate than the maximally decimated equal-passbands scheme. Second, when the scheme is tested for white and coloured inputs using a low number of bands, it does not yield good results; but when the number of bands is increased, the speed of convergence is enhanced. Third, the scheme is tested for quick changes. It is shown that the performance of the proposed scheme is similar to that of the equal-passbands scheme. Fourth, the scheme is also tested in a stationary state. The experimental results confirm the theoretical work. For more challenging scenarios, an unequal-passbands scheme with over-sampled decimation is proposed; the greater number of bands, the more efficient the separation. The results are compared to the currently best performing method. Second, an experimental comparison is made between the proposed multiband scheme and the conventional scheme. The results show that the convergence speed and the signal-to-interference ratio of the proposed scheme are higher than that of the conventional scheme, and the computation cost is lower than that of the conventional scheme.
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Safia, Abdelmounaime. "Développement d’un modèle d’analyse de texture multibande." Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5990.
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Résumé : En télédétection, la texture facilite l’identification des classes de surfaces sur des critères de similitude d’organisation spatiale des pixels. Les méthodes d’analyse texturale utilisées en télédétection et en traitement d’image en général sont principalement proposées pour extraire la texture dans une seule bande à la fois. Pour les images multispectrales, ceci revient à extraire la texture dans chaque bande spectrale séparément. Cette stratégie ignore la dépendance qui existe entre la texture des différentes bandes (texture inter-bande) qui peut être une source d’information additionnelle aux côtés de l’information texturale classique intra-bande. La prise en charge de la texture multibande (intra- et inter-bande) engendre une complexité calculatoire importante.
Dans sa recherche de solution pour l’analyse de la texture multibande, ce projet de thèse revient vers les aspects fondamentaux de l’analyse de la texture, afin de proposer un modèle de texture qui possède intrinsèquement une complexité calculatoire réduite, et cela indépendamment de l’aspect multibande de la texture. Une solution pour la texture multibande est ensuite greffée sur ce nouveau modèle, de manière à lui permettre d’hériter de sa complexité calculatoire réduite.
La première partie de ce projet de recherche introduit donc un nouveau modèle l’analyse de texture appelé modèle d’unité texturale compacte (en anglais : Compact Texture Unit, C-TU). Le C-TU prend comme point de départ le modèle de spectre de texture et propose une réduction significative de sa complexité. Cette réduction est atteinte en proposant une solution générale pour une codification de la texture avec la seule information d’occurrence, sans l’information structurelle. En prenant avantage de la grande efficacité calculatoire du modèle de C-TU développé, un nouvel indice qui analyse la texture multibande comme un ensemble indissociable d’interactions spatiales intra- et inter-bandes est proposé. Cet indice, dit C-TU multibande, utilise la notion de voisinage multibande afin de comparer le pixel central avec ses voisins dans la même bande et avec ceux des autres bandes spectrales. Ceci permet à l’indice de C-TU multibande d’extraire la texture de plusieurs bandes simultanément. Finalement, une nouvelle base de données de textures couleurs multibandes est proposée, pour une validation des méthodes texturales multibandes. Une série de tests visant principalement à évaluer la qualité discriminante des solutions proposées a été conduite. L’ensemble des résultats obtenus dont nous faisons rapport ici confirme que le modèle de C-TU proposé ainsi que sa version multibande sont des outils performants pour l’analyse de la texture en télédétection et en traitement d’images en général. Les tests ont également démontré que la nouvelle base de données de textures multibande possède toutes les caractéristiques nécessaires pour être utilisée en validation des méthodes de texture multibande. // Abstract : In multispectral images, texture is typically extracted independently in each band using existing grayscale texture methods. However, reducing texture of multispectral images into a set of independent grayscale texture ignores inter-band spatial interactions which can be a valuable source of information. The main obstacle for characterizing texture as intra- and inter-band spatial interactions is that the required calculations are cumbersome. In the first part of this PhD thesis, a new texture model named the Compact Texture Unit (C-TU) model was proposed. The C-TU model is a general solution for the texture spectrum model, in order to decrease its computational complexity. This simplification comes from the fact that the C-TU model characterizes texture using only statistical information, while the texture spectrum model uses both statistical and structural information. The proposed model was evaluated using a new monoband C-TU descriptor in the context of texture classification and image retrieval. Results showed that the monoband C-TU descriptor that uses the proposed C-TU model provides performances equivalent to those delivered by the texture spectrum model but with much more lower complexity.
The calculation efficiency of the proposed C-TU model is exploited in the second part of this thesis in order to propose a new descriptor for multiband texture characterization. This descriptor, named multiband C-TU, extracts texture as a set of intra- and inter-band spatial interactions simultaneously. The multiband C-TU descriptor is very simple to extract and computationally efficient. The proposed descriptor was compared with three strategies commonly adopted in remote sensing. The first is extracting texture using panchromatic data; the second is extracting texture separately from few newbands obtained by principal components transform; and the third is extracting texture separately in each spectral band. These strategies were applied using cooccurrence matrix and monoband compact texture descriptors. For all experiments, the proposed descriptor provided the best results. In the last part of this thesis, a new color texture images database is developed, named Multiband Brodatz Texture database. Images from this database have two important characteristics. First, their chromatic content, even if it is rich, does not have discriminative value, yet it contributes to form texture. Second, their textural content is characterized by high intra- and inter-band variation. These two characteristics make this database ideal for multiband texture analysis without the influence of color information.
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Sun, Hanwu. "Adaptive techniques for multiband parameter estimation and extraction." Thesis, University of Westminster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296126.
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Gebremicael, Kibrom Negash. "Compressive sensing based multiband RF power amplifier linearisation." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730827.
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Jonsson, Joakim. "Detecting Cardiac Pulsatility and Respiration using Multiband fMRI." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-149863.
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Purpose: Arterial stiffening poses an increased risk of cerebrovascular diseases, cognitive impairments, and even dementia as cardiac pulsations reach further into the brain causing white matter hyperintensities and microbleeds. Therefore it is of interest to obtain methods to estimate and map cardiac related pulsatility in the brain. Improvements of functional magnetic resonance imaging (fMRI) sequences is potentially allowing detection of rapid physiological processes in the echo-planar imaging (EPI) signal in the brainthrough a higher sampling rate. Specifically in this thesis, estimation and localization of cardiac pulsation and respiration is conducted through analysis of resting state data obtained with a multiband EPI sequence that permits whole brain imaging at a shorter repetition time (TR) than conventional EPI. The origin of these physiological signals are likely a mixture of inflow and compartment volume shifts during the cardiac- and respiratory cycles. As the amount of physiologically related signal in the multiband sequence used at the Biomedical Engineering Dept. R&D, Umeå University Hospital is unknown, the aim of this project is to find and map cardiac pulsatility and respiration for future research. Methods: Multiband fMRI data from 8 subjects was used, collected in a 3 Tesla scanner using a 32-channel head coil. The physiological signals were estimated through an algorithm that was developed to down-sample and temporally shift copies of simultaneous recordings of pulse and respiration. These signals were obtained using the scanner’s built-in pulse oximeter and a respiration belt. The shifted copies were voxel-wise, and slice by slice, correlated to the fMRI data using Pearson correlation. The time shift yielding maximum mean correlation within the brain was, for each slice, used to create statistical maps for significant voxels to show the localization and magnitude of correlation for cardiac pulsation andrespiration. Results: Many voxels around and nearby larger vessels and ventricles were highly correlated with the down-sampled, time shifted signals of the cardiac pulsation for all subjects. The cardiac pulsation maps resembled cerebral vasculature and were mostly localized around the Circle of Willis, brainstem, and the ventricles. Respiration signal was also highly correlated, and spatially located at the sides of the brain although mostly concentrated at the parietal- and occipital lobes. Conclusion: The results demonstrated that many voxels in the brain were highly correlated with cardiac pulsation and respiration using multiband EPI, and the statistical maps revealed distinct patterns for both of the physiological signals. This method and results for mapping cardiac related pulsatility, and respiration could be used for future research in order to better understand cerebral diseases and impairments, and alsoto improve fMRI filtering. Keywords: Arterial stiffness, Functional magnetic resonance imaging, Resting state, Multiband, CardiacPulsation, Respiration, Correlation analysisSyfte: Arteriell förstyvning medför en ökad risk för cerebrovaskulära sjukdomar, kognitiva störningar och till och med demens då hjärtpulsationer når längre in i hjärnan orsakar vit materia hyperintensiteter och mikroblödningar. Av detta skäl är det därför av intresse att ta fram metoder för att estimera och kartlägga hjärtrelaterad pulsationer i hjärnan. Förbättringar av funktionella magnetresonanstomografi (fMRI) sekvenser kan möjliggöra detektering av snabba fysiologiska processer i den eko-planära (EPI) signalen i hjärnan genom en högre samplingsfrekvens. Specifikt i denna uppsats, utförs en skattning och lokalisering av hjärtpulsation och respiration genom analys av ’resting state’ data erhållet av en multiband-EPI sekvens som tillåter bildgivning av hela hjärnan med en kortare repetitionstid (TR) än konventionell EPI. Ursprunget avdessa fysiologiska signaler är sannolikt från en blandning av flöde- och volymsförändringar under hjärt- och respirationscyklerna. Då mängden av fysiologiskt relaterad signaler i multiband sekvensen, som används på Biomedicinska avdelningen, FoU Umeå Universitetssjukhust, är okänd så är målet med projektet att hitta och kartlägga hjärtpulsation och respiration för framtida forskning. Metod: Multiband fMRI data från 8 personer användes, insamlade från en 3 Tesla scanner med en 32-kanals huvudspole. De fysiologiska signalerna uppskattades genom en algoritm som utveckades för att sampla ned och tidsförskjuta kopior av simultant tagna signaler av puls och respiration. Dessa signaler samlades in med skannerns inbyggda pulsoximeter och andningsband. De förskjutna kopiorna var voxelvis, snitt för snitt, korrelerade med fMRI datat med användning av Pearson-korrelation. Det tidsskift somför varje snitt resulterade i maximal medelkorrelation i hjärnan användes för att skapa statistiska kartor, med endast signifikanta voxlar, för att visa var och hur mycket korrelation av hjärtpulsation och respiration som finns. Resultat: Många voxlar runt och nära större kärl och ventriklar var för alla personer starkt korrelerade medde samtidigt tagna, och tidsförskjutna signalerna av hjärtpulsation. Pulsationskartorna liknade cerebral vaskulatur och var mestadels lokaliserade kring Willis ring, hjärnstammen och ventriklar. Respirationssignalen var även starkt korrelerad och lokaliserad på sidorna av hjärnan, mestadels koncentrerat vid parietal- och occipital loberna. Slutsats: Resultaten visade att många voxlar i hjärnan var starkt korrelerade med hjärtpulsation och respiration vid användning av multiband EPI, och de statistiska kartorna avslöjade distinkta mönster för de båda fysiologiska signalerna. Den framtagna metoden och dess resultat för kartläggning av hjärtrelaterade pulsationer och respiration kan användas i framtida forskning i syfte att bättre förstå cerebrala sjukdomar och nedsättning, även för att förbättre fMRI filtrering. Nyckelord: Arteriell förstyvning, Funktionell magnetresonanstomografi, Resting state, Multiband, Hjärtpulsation, Andning, Korrelationsanalys
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To, Duy-Quang. "Advanced k.p multiband methods for semiconductor-based spinorbitronics." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX001.
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Ce travail de thèse est essentiellement consacré au développement de la théorie de transport tunnel k.p 14, 30 et 40 bandes pour une application à la spinorbitronique avec semiconducteur. La spinorbitronique associe les effets de spin et d’orbite, qui par l’intermédiaire du couplage spin-orbite, introduit des propriétés de transport nouvelles comme les effets Hall de spin et tunnel Hall anormal. Ce dernier se caractérise par une déflection de la trajectoire des porteurs polarisés selon la direction transverse de leur flux. D’autres effets caractéristiques concernent i) les mécanismes de transfert de spin permettant de commuter une aimantation par transfert de moment angulaire, généralisant ainsi le transfert de spin ainsi que ii) la conversion spin-charge médiés par les termes Rashba ou Dresselhaus. Dans ce cadre, notre théorie de transport tunnel est adaptable aux hétérostructures semiconductrices, magnétiques ou non, traitant d’une simple interface ou de jonctions tunnel. Elle permet de tenir compte de façon fine des interactions spin-orbite de cœur et d’interface. Elle utilise de façon générale l’introduction de bandes hautes supplémentaires, dites fantômes, pour traiter les états spurious inhérents à la théorie k.p multibandes. Outre l’introduction des états ‘fantômes’ ne déformant ni la structure électronique, ni le transport polarisé, notre approche utilise la continuité des composantes des fonctions d’onde à chaque interface ainsi que le raccordement des composantes du courant d’onde selon la symétrie des interfaces soit par 1) la continuité des composantes du courant d’onde (extension de la théorie Ben Daniel Duke), 2) les conditions de raccordement obéissant à une symétrie C2v par mélange cd trous lourds/légers dans la bande de valence (conditions d’Ivchenko) ou 3) discontinuité des bandes p ‘hautes’. Nous démontrons, en outre, l’équivalence des conditions de continuité pour le cas de puits quantiques III-V de type AlAs/GaAs/AlAs ce qui représente ainsi une généralisation de résultats précédents développés en 14 bandes.L’ensemble de ce travail de thèse analytique et numérique, comportent plusieurs démonstrations importantes. Nous montrons que notre théorie permet de décrire le transport de spin d’états couplés spin-orbite dans les hétérostructures semiconductrices d’axe de croissance (100) ou (110). Ces résultats sont notamment matérialisés par les calculs les trois composantes du courant de spin dans les barrières III-V (GaAs, AlAs) jouant le rôle de déphaseur de spin. Les calculs que nous développons montrent en effet, comme le prévoit la théorie analytique, une rotation vectorielle de la matrice densité de spin dans l’épaisseur de la barrière et comme prévue par l’application d’un champ e spin-orbite effectif de Dresselhaus parallèle au plan de la barrière.Notre théorie est également comparée avec succès aux calculs de perturbation multibandes utilisant les fonctions de Green pour le transport pour traiter les mécanismes de l’effet tunnel Hall anormal dans la bande conduction et dans la bande de valence. Les résultats sont remarquables de fidélité ce qui montre la puissance de la technique utilisée. Nous calculons également les propriétés de courant de spin dans les jonctions tunnel ferromagnétiques à base de GaMnAs pour en déduire le couple de transfert de spin responsable de la commutation de l’élément ferromagnétique fin. Nous montrons par exemple, comment les composantes de spin transverses du courant sont pertinents pour commuter une aimantation. Enfin, nous avons adapté notre théorie de transport aux structures III-V pour calculer les états confinés de puits quantiques dans la bande de conduction et bande de valence. Nous comparons avec succès, nos résultats multibandes à l’état de l’art 6 bandes et 14 bandes, sur l’anisotropie optique de l’absorption entre les directions (110 et (1-10) du champ électrique lorsque la symétrie de l’hétérostructure est réduite à une symétrie C2vThis thesis work is essentially devoted to the development of the tunneling theory k.p 14, 30 and 40 bands for a spinorbitronic application with semiconductor. Spinorbitronic combines the effects of spin and orbit, which via spin-orbit coupling, introduces new transport properties such as spin Hall and anomalous Hall effects. The latter is characterized by a deflection of the trajectory of polarized carriers in the transverse direction of their flow. Other characteristic effects concern i) the spin transfer mechanisms for switching angular momentum transfer magnetization, thus generalizing spin transfer as well as ii) spin-charge conversion mediated by the terms Rashba or Dresselhaus. In this context, our tunnel transport theory is adaptable to semiconductor heterostructures, magnetic or not, dealing with a simple interface or tunnel junctions. It allows to take into account in a fine way the spin-orbit interactions of heart and interface. It generally uses the introduction of additional high bands, called ghosts, to deal with the spurious states inherent in the multiband k.p theory. Apart from the introduction of the "spurious" states neither deforming the electronic structure nor the polarized transport, our approach uses the continuity of the components of the wave functions at each interface and the connection of the components of wave current according to symmetry interfaces either by 1) the continuity of the components of wave current (extension of Ben Daniel Duke theory), 2) the connection conditions obeying a C2v symmetry by mixing heavy holes cd / light in the valence band (conditions from Ivchenko) or 3) discontinuity of the 'high' bands. We also demonstrate the equivalence of the continuity conditions for the case of AlAs / GaAs / AlAs III-V quantum wells, which represents a generalization of previous results developed in 14 bands.The whole of this work of analytical and numerical thesis, include several important demonstrations. We show that our theory can be used to describe the spin transport of spin-orbit coupled states in growth axis (100) or (110) semiconductor heterostructures. These results are notably materialized by the calculations of the three components of the spin current in the III-V barriers (GaAs, AlAs) acting as spin phase-shifters. Calculations show that we develop in effect, as provided by the analytic theory, a vector rotation of the spin density matrix in the thickness of the barrier and as provided by the application of an effective spin-orbit field Dresselhaus parallel to the plane of the barrier.Our theory is also successfully compared to the multiband perturbation calculations using Green's transport functions to address the mechanisms of abnormal Hall tunnel effect in the conduction band and the valence band. The results are remarkable of fidelity which shows the power of the technique used. We also calculate spin current properties in GaMnAs-based ferromagnetic tunnel junctions to derive the spin transfer torque responsible for switching the fine ferromagnetic element. We show, for example, how the transverse spin components of the current are relevant to switch a magnetization. Finally, we adapted our transport theory to III-V structures to compute confined quantum well states in the conduction band and valence band. We successfully compare our state-of-the-art 6-band and 14-band multiband results on the optical anisotropy of absorption between the directions (110 and (1-10) of the electric field when the symmetry of the heterostructure is reduced to C2v symmetry
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Shakya, Bikash. "A Study of Multiband Indoor Radio Distribution System." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174864.
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The mobile indoor traffic are increasing exponentially which is the current challenge inindoor coverage and design for most of the researchers and business companies todevelop further. There are different trade-off to provide different indoor services withthe use of different repeater system, distributed antenna network (active and passive),macro cells indoor penetrations and many more. As the use of energy effective materialsfor construction of buildings have made a blockage of RF signals from macro cells,usually a separate installations are done to provide indoor coverage for differentservices such as TRTRA, GSM, UNTS, LTE and WLAN in indoor environments forlarge campuses, industrial complex, sports arena, tunnels and office buildings. Thisseparate installations increases the cost, installation space and time which can be solvedusing the same infrastructure to provide multiple of mobile indoor solutions using smartintegrated solutions where many mobile services can be distributed indoor using thesame distributed antenna network using active and passive networks.This thesis investigates the advantage and disadvantage of different types of active andpassive distributed antenna system with the integrated antenna network to compare thecoverage and cost analysis. The coverage analysis was done to compare the RSSI levelby adding different frequency bands into the indoor network for both active and passiveDAS design. Different types of sample design model was used to verify the coverageanalysis. It can be seen from the coverage analysis that an integrated system with all inone solution also has a better coverage compared to typical active and passive designwhich can be used in future in building design as One Net Solution. Also the costanalysis was done for both CAPEX and OPEX to find the cost estimation for differentindoor models. It showed that the integrated solution is the most expensive solution butif it has a case of large design venues, then integrate active solution can be the onlysolutions. Passive design cannot cover large scale areas. It is suitable only for small andmedium sized venues.
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Renosto, Sergio Tuan. "Estudo da supercondutividade em diboretos de metais de transição (MeB2), com protótipo ALB2 e suas variações." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/97/97135/tde-05082015-161044/.
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O grupo de diboretos isoestruturais ao MgB2 com estrutura representada pelo protótipo AlB2 é considerado candidato à supercondutividade. Contudo, a existência do estado supercondutor é um fenômeno raro nesse grupo de materiais, de fato a grande maioria dos diboretos de metais de transição é caracterizada por um Tc menor que 0,7 K. Nesse grupo, os compostos normais HfB2, VB2, YB2 e ZrB2 exibem assinatura do comportamento paramagnético de Pauli em baixas temperaturas. Nesse trabalho é mostrado que a substituição parcial do metal (Hf e Zr) por V nas amostras M1-xVxB2, gera distorções da rede cristalina, com o surgimento de um estado supercondutor volumétrico. As medidas magnéticas, elétricas e térmicas revelam um Tc máximo atingindo 8,7 e 9,3 K para as respectivas amostras de composição Zr0,96V0,04B2 e Hf0,97V0,03B2, com valores elevados de ? 0Hc2(0) (~16 e ~21 T, respectivamente). Nessas amostras, os resultados a cerca do comportamento do ? 0Hc1 (T), do Cp(T) e da VHall (T), e medidas de ETS (electronic tunneling spectroscopy) em um monocristal, revelam a claras assinaturas da supercondutividade multibanda, tal como é reportado para o MgB2. Ainda, resultados mostram a que a existência do estado supercondutor no ZrB2 parece não ser uma exclusividade da substituição por V, já que é observada também na amostra de Zr0,96Y0,04B2, cujo Tc atinge 6,7 K novamente com assinatura de comportamento multibanda. Também são mostrados os resultados da existência dos comportamentos magnéticos competitivos nas amostras do sistema Zr1-xAlxB2, com um surpreendente ordenamento ferromagnético. Nesse mesmo cenário, também é mostrado que substituição de Nb por Ni é hábil em elevar a temperatura crítica do composto NbB2-? de 3,6 K para 6,0 K. Já em outros boretos, como nos sistemas Th1-xMxB12 (M = Zr, Sc, Y, Ti Hf) em condições especiais de síntese e substituição a fase ThB12 (inexistente no equilíbrio) pode ser estabilizada, onde se observa para amostra Th0,97Zr0,03B12 um Tc próximo a 5,5 K e comportamento supercondutor BCS, porém com um baixo valor do parâmetro k o que abre discussão para uma classe nova de supercondutores do tipo 1,5.The diborides group isostructural to MgB2 represented by AlB2 prototype structure are considered important candidates for superconductivity. However, the existence of the superconducting state is a rare phenomenon in this group of materials, indeed the majority of transition metal diborides are characterized by a Tc lower than 0.7 K. In this group, the normal compounds HfB2, VB2, YB2, and ZrB2 exhibit signature Pauli paramagnetic behavior at low temperatures. In this work it is shown that the metal partial substitution (Hf and Zr) by V in M1-xVxB2 samples generates distortions of the crystal lattice, with the emergence of a bulk superconducting state. The magnetic, electric and thermal measurements reveal a maximum Tc reaching 8.7 and 9.3 K for the respective samples Zr0.96V0.04B2 and Hf0.97V0.03B2 composition with high values of ? 0Hc2(0) (~ 16 and ~ 21 T, respectively). In these samples, the results about the behavior ? 0Hc1 (T), Cp(T), and VHall (T); and ETS (electronic tunneling spectroscopy) measurements in a single crystal; reveal a clear signatures of multiband superconductivity such as reported to the MgB2. Furthermore, the results show that the existence of the superconducting state ZrB2 appears to be not exclusive by V substitution, it is also observed in the sample Zr0.96Y0.04B2 whose Tc reaches 6.7 K again with signature multiband behavior. Also shown are the results of the existence of competitive magnetic behavior in samples of Zr1-xAlxB2 system, with a surprising ferromagnetic ordering. In this same scenario, it is also shown that substitution of Nb by Ni is able to raise the critical temperature of the NbB2-? compound from 3.6 K to 6.0 K. Since other borides as in Th1- xMxB12 (M = Zr, Sc, Y, Ti Hf) systems, in special conditions of synthesis and substitution the ThB12 phase (non-existent in the equilibrium conditions) can be stabilized, which is observed to Th0.97Zr0.03B12 sample with Tc close to 5.5 K and BCS superconducting behavior, but with a low of the k parameter value opening discussion for a new class of 1.5 type superconductors.
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Junior, Pedro Luiz Frare. "Seleção de múltiplos planos em tomografia por ressonância magnética nuclear." Universidade de São Paulo, 1990. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-06122013-150646/.
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Apresentamos um estudo e a implementação de três técnicas destinadas a seleção de múltiplos planos, com objetivo de otimizar a tomografia por RMN. A primeira utiliza a excitação simultânea de múltiplos planos, sendo cada plano codificado com uma fase pré-determinada e a informação destes decodificada a posteriori através da combinação linear dos dados de n experimentos realizados. A segunda utiliza-se da excitação simultânea de múltiplos planos, como na técnica anterior, porém esses planos são adquiridos na presença de um gradiente de leitura oblíquo, que permite a obtenção simultânea dos sinais destes planos sem necessidade de pós-processamento. A terceira técnica usa a multiplexação de freqüências de excitação no tempo, isto é, diferentemente das teorias anteriores, excitam-se diferentes planos sucessivamente, durante o tempo de repetição de uma seqüência de aquisição, permitindo a aquisição de vários planos ao tempo de um único. A construção e o uso de um phantom destinado a caracterização do equipamento também é discutida. Esse phantom possibilita por exemplo: a determinação da largura do plano selecionado, o espaçamento entre os planos e o perfil destes, entre outros. Abordamos também, vários aspectos técnicos necessários a uma melhor performance do tomógrafo, tais como: circuitos de recepção e ressoadores. Apresentamos finalmente, uma discussão introdutória e os primeiros resultados experimentais já obtidos com a técnica de excitação adiabática com gradiente modulado (GMAX), utilizando bobinas de superfícieWe present the study and the implementation of three techniques HIS for the selection of multi-slice, aiming the optimization of the NMR tomography . The first technique uses the simultaneous excitation of multiple slices, being each plane encoded with a pre determined phase for a latter decodification of the information by the linear combination of n experiments. The second one makes use of the multi-slice simultaneous excitation, like the first one, but the slices are acquired in the presence of an oblique reading gradient , which provides us the multi-slice signal without any further computer processing. The third technique uses frequency multiplexed excitation, that is, different slices are successively excited during the repetition time of an acquisition sequence, making possible multi-slice acquisition at the same time of a single slice The construction and the use of a phantom for the equipment characterizations are discussed too. With this phantom we can determine the thickness of the selected slice, the spacing between the slices and the their shapes. Many technical aspects necessary for an improvement of the tomography performance, like reception circuits and resonators, are discussed. At last, we present a brief introduction to the gradient modulated adiabatic excitation (GMAX) technique and the first results ever obtained with it, using surface coils
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Gemio, Valero Joan. "Multiband and Silicon Integrated Antennas for Wireless Sensor Networks." Doctoral thesis, Universitat Autònoma de Barcelona, 2011. http://hdl.handle.net/10803/79096.
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Les tecnologies sense fils han provocat una important revolució en el món de les xarxes i serveis de telecomunicació. Han apareguts nous sistemes com els telèfons mòbils d'última generació o les xarxes LAN sense fils que han estat acceptats amb entusiasme per la població. En particular, l'ús de xarxes de sensors (per controlar la temperatura, per a detectar places lliures d'aparcament, etc.) està creixent ràpidament . Aquesta tesi es centra en el disseny d'antenes per a xarxes de sensors distribuïts. En concret s'analitza un sistema on els sensors remots estan connectats a una unitat central utilitzant un radio enllaç operant en la banda ISM de 5,8 GHz, i la unitat central envia la informació recollida a Internet a través d'una connexió WLAN. A la unitat central es necessiten antenes multibanda per cobrir diverses bandes de freqüències amb un únic element radiant. En aquesta tesi es presenten dues solucions per obtenir aquest comportament multibanda: Monopols amb pla de massa fractal i monopols carregats amb ressonadors. S'han fabricat i mesurat diferents prototips que cobreixen les necessitats del sistema. Els sensors han de ser dispositius de reduïdes dimensions i baix cost. Una bona opció per aconseguir aquests requisits és l'ús d'antenes integrades en silici fabricades amb una tecnologia CMOS estàndard. En primer lloc s'analitzen els principals problemes de la integració de l'antena en silici, i a continuació es presenta una possible solució per millorar l'eficiència juntament amb un estudi de la degradació introduïda per altres components quan aquests es fabriquen en el mateix xip que l’antena. Les mesures dels prototips fabricats demostren que la integració de l'antena en la banda de 5,8 GHz és factible, obtenint un abast d'alguns metres.
Cada vegada és una realitat més propera el fet de tenir sensors implantats en el cos. Per aquest motiu, l’última part d'aquesta tesi es dedica a estudiar els efectes del cos sobre antenes situades en el seu interior i avaluar les pèrdues de propagació addicionals introduïdes pels teixits humans.Las tecnologías inalámbricas han provocado una importante revolución en el mundo de las redes y servicios de telecomunicación. Han aparecidos nuevos sistemas, como los teléfonos móviles de última generación o las redes LAN inalámbricas, que han sido aceptados con entusiasmo por la población. En particular, el uso de redes de sensores (para controlar la temperatura, para detectar plazas libres de aparcamiento, etc.) está creciendo rápidamente. Esta tesis se centra en el diseño de antenas para redes de sensores inalámbricos distribuidos. EN concreto se analiza un sistema donde los sensores están conectados a una unidad central utilizando un enlace inalámbrico en la banda ISM de 5.8 GHz, y la unidad central envía la información recogida a Internet a través de una conexión WLAN. En la unidad central se necesitan antenas multibanda para dar servicio a varias bandas de frecuencias con un único elemento radiante. En esta tesis se presentan dos soluciones para obtener este comportamiento multibanda: Monopolos con plano de masa fractal y monopolos cargados con resonadores. Se han fabricado y medido diferentes prototipos que cubren las necesidades del sistema. En los sensores se desean dispositivos de reducidas dimensiones y bajo coste. Una buena opción para lograr estos requisitos es el uso de antenas integradas en silicio fabricadas con una tecnología CMOS estándar. En primer lugar se analizan los principales problemas de la integración de la antena en silicio, y a continuación se presenta una posible solución para mejorar la eficiencia de radiación junto con un estudio de la degradación introducida por otros componentes cuando éstos se fabrican en el mismo chip que la antena. Las medidas de los prototipos fabricados demuestran que la integración de la antena en la banda de 5,8 GHz usando una tecnología CMOS es factible, obteniendo unos alcances de algunos metros incluso cuando la antena se fabrica junto con otros elementos integrados en el mismo chip. Cada vez es una realidad más cercana el hecho de poder tener sensores implantados en el cuerpo. Por este motivo, la última parte de esta tesis se dedica a estudiar los efectos del cuerpo sobre antenas situadas en su interior y evaluar las pérdidas de propagación adicionales introducida por los tejidos humanos.
Wireless technologies have triggered an important revolution in the world of telecommunication networks and services. New systems, such as the latest generation mobile phones or wireless LANs, have appeared being enthusiastically accepted by people. In particular, applications related to remote sensor networks are growing rapidly (for temperature monitoring, the detection of free parking spaces, etc.). This thesis is focused on antenna design for distributed wireless sensor networks. The remote sensors we are considering are connected to a central unit using a wireless link in the 5.8 GHz ISM band and the central unit transmits the collected information to the Internet via a WLAN connection. In the central unit multiband antennas are necessary to cover several frequency bands with a single radiating element. Two solutions to obtain this multiband performance are proposed: fractal-based ground planes and resonator loaded monopoles. Several novel antennas that easily meet the system requirements are manufactured and measured. For remote sensors small dimensions and low costs are desired. The use of silicon integrated antennas fabricated with standard CMOS technology is a good choice to achieve these requirements. First, the main problems of antenna integration are discussed and, then a possible solution to improve the antenna efficiency is presented together with a study of the effects of other elements integrated in the same chip with the antenna. The measurements of the manufactured prototypes demonstrate that antenna integration at 5.8 GHz is feasible, and that system ranges of some meters can be obtained even when the antenna is fabricated together with other elements integrated in the same chip. The possibility of having some of the sensors implanted inside the body will be a reality in the near future, for this reason the particular case of implanted antennas is also analyzed. The last part of this thesis is devoted to study the body effects on antenna performance and evaluate the additional propagation losses introduced by the body tissues.
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Jasper, David Brian. "RF pHEMT Switch Model for Multiband Cell Phone Circuits." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-11032004-220504/.
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Simulation of Radio Frequency Switches used in the cellular phone industry is the main focus of this study. The RF pHEMT?s used in an antenna switch for multiband cell phone circuits requires the use of an accurate model during simulation of the RF system. The pHEMT model extracted in this study utilizes theoretical methods within the extraction software and an analysis of simulated data and measured data. This study describes the techniques of calibration, model extraction, and data analysis.
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Martin, Gregory Russell. "Studies of real-time multiband adaptive gain hearing aids." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12920.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (leaves 71-72).
by Gregory Russell Martin.
M.S.
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Nepaya, Leokadia Ndeapo Popyeni. "Practical realisation of multiband planar filters on multilayer substrates." Doctoral thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/30347.
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This research presents the design of planar microwave filters implemented on microstrip multi-layer technology. These should be able to attain and realize specified essential requirements such as multi-band operation, compact size, and without significant deteriorated filter performance in comparison with single-band filters. The focus is placed on new synthesis and design procedures for multiband responses. In some cases, the possibility to include re-configurable characteristics of these filters is required. The focus of the research is entirely on examining the properties and implications of a previously proposed reactance transform method for multiband filter synthesis. The research commences with reviews of multi-band filter synthesis methods. The research specifically examines a full analytical synthesis approach based on reactance transforms method and the implications for practical design approaches Investigations on narrowband with coupled resonator filters representation and wide-band with quasi-lumped element filters representation of up to quad-bands based on reactance transform method are undertaken. With the emphasis on practical aspects such as losses and selectivity, which are related to the physical implementation on multi-layer substrate, the key differences between multiband and single-band filters based on a reactance transform are highlighted. It is illustrated that, in addition to the order of the basis filter, selectivity is influenced by the number of bands, the spacing of the bands and the relative bandwidths. It is also shown that loss has a significant effect on multiband filter responses, in a somewhat different way from that for single-band filters. Physical designs of narrow- band coupled resonators filters are implemented with the aim of examining the degrees of design freedom for multi-layer substrate design, considering the resonance properties and couplings between resonators and considering loss for resonators on different layers. Mercurywave 9350, a low-cost multi-layer substrate is chosen and deemed suitable for a number of reasons, including relatively constant permittivity over frequency. The designs consist of novel topologies: parallel connected multi-path referred to as transversal and also all-pole topologies. A transversal topology includes a dual-band dual-path design as well as a dual-band triple-path design while the all-pole topology is a quad-band design. The research explores re-configurable characteristics of narrow-band coupled resonators of a dual-band dual-path design. A process to obtain a re-configurable multi-band filter with electronically selected pass-bands, based on a reactance transform method for coupled resonator filters, is described. A dual-band multi-band filter realized on multi-layer substrate is designed for passive space applications and reconfigurability is demonstrated using a pre-selection method. For wide-band, quasi-lumped element filters are realized on multi-layer substrate, the inductors are implemented as rectangular spiral inductors and Capacitors as broadside coupling plates connected from two different layers through metallic vias. Parasitic that may influence the relative bandwidths.
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Saleem, Rashid. "Towards an end-to-end multiband OFDM system analysis." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/towards-an-endtoend-multiband-ofdm-system-analysis(e711f32f-1ac6-4b48-8f4e-58309c0482d3).html.
Full textAbstract:
Ultra Wideband (UWB) communication has recently drawn considerable attention from academia and industry. This is mainly owing to the ultra high speeds and cognitive features it could offer. The employability of UWB in numerous areas including but not limited to Wireless Personal Area Networks, WPAN's, Body Area Networks, BAN's, radar and medical imaging etc. has opened several avenues of research and development. However, still there is a disagreement on the standardization of UWB. Two contesting radios for UWB are Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) and DS-UWB (Direct Sequence Ultra Wideband). As nearly all of the reported research on UWB hasbeen about a very narrow/specific area of the communication system, this thesis looks at the end-to-end performance of an MB-OFDM approach. The overall aim of this project has been to first focus on three different aspects i.e. interference, antenna and propagation aspects of an MB-OFDM system individually and then present a holistic or an end-to-end system analysis finally. In the first phase of the project the author investigated the performance of MB-OFDM system under the effect of his proposed generic or technology non-specific interference. Avoiding the conventional Gaussian approximation, the author has employed an advanced stochastic method. A total of two approaches have been presented in this phase of the project. The first approach is an indirect one which involves the Moment Generating Functions (MGF's) of the Signal-to-Interference-plus-Noise-Ratio (SINR) and the Probability Density Function (pdf) of the SINR to calculate the Average Probabilities of Error of an MB-OFDM system under the influence of proposed generic interference. This approach assumed a specific two-dimensional Poisson spatial/geometric placement of interferers around the victim MB-OFDM receiver. The second approach is a direct approach and extends the first approach by employing a wider class of generic interference. In the second phase of the work the author designed, simulated, prototyped and tested novel compact monopole planar antennas for UWB application. In this phase of the research, compact antennas for the UWB application are presented. These designs employ low-loss Rogers duroid substrates and are fed by Copla-nar Waveguides. The antennas have a proposed feed-line to the main radiating element transition region. This transition region is formed by a special step-generating function-set called the "Inverse Parabolic Step Sequence" or IPSS. These IPSS-based antennas are simulated, prototyped and then tested in the ane-choic chamber. An empirical approach, aimed to further miniaturize IPSS-based antennas, was also derived in this phase of the project. The empirical approach has been applied to derive the design of a further miniaturized antenna. More-over, an electrical miniaturization limit has been concluded for the IPSS-based antennas. The third phase of the project has investigated the effect of the indoor furnishing on the distribution of the elevation Angle-of-Arrival (AOA) of the rays at the receiver. Previously, constant distributions for the AOA of the rays in the elevation direction had been reported. This phase of the research has proposed that the AOA distribution is not fixed. It is established by the author that the indoor elevation AOA distributions depend on the discrete levels of furnishing. A joint time-angle-furnishing channel model is presented in this research phase. In addition, this phase of the thesis proposes two vectorial or any direction AOA distributions for the UWB indoor environments. Finally, the last phase of this thesis is presented. As stated earlier, the overall aim of the project has been to look at three individual aspects of an MB-OFDM system, initially, and then look at the holistic system, finally. Therefore, this final phase of the research presents an end-to-end MB-OFDM system analysis. The interference analysis of the first phase of the project is revisited to re-calculate the probability of bit error with realistic/measured path loss exponents which have been reported in the existing literature. In this method, Gaussian Quadrature Rule based approximations are computed for the average probability of bit error. Last but not the least, an end-to-end or comprehensive system equation/impulse response is presented. The proposed system equation covers more aspects of an indoor UWB system than reported in the existing literature.
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Karlsson, Alexander, and Alexander Vestlund. "Integrated Multiband High Gain and Stable GaN Input Matching Network." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128423.
Full textAbstract:
This bachelor thesis covers the basics of constructing a stable transistor based amplifying circuit. The task was to design an input match in order to increase the gain of a specific transistor. This transistor model, GH60015D is developed by Cree Inc. When this transistor is stabilized much of the original gain is reduced. The main problem is that it fails to deliver high amounts of gain over a wide band while remaining stable. To counter this, an input match with multiband purposes is designed in order to increase the gain over specific frequency bands. The thesis covers the basics to design an input matching network for a transistor and how one can analyze circuits in more detail in order to get as a realistic simulation as possible. In this project ADS software and models of the CH60015D are used in order to simulate circuits intended for implementation that is meant to be built on a glass-substrate. The desired result of the work is to obtain as much large signal gain as possible over the frequency bands 2.11-2.17GHz and 2.62-2.69GHz while maintaining stability. The results of this report show methods for maintaining out of band stability, while decreasing stability margin at specific bands. Decreasing stability can enhance the gain under controlled conditions. The large signal gain obtained at approximately 15W output power for both selected frequency bands are around 15.2dB.Detta kandidatexamensarbete omfattar grunderna i hur en stabil transistorbaserad förstärkarkrets designas. Uppgiften var att designa en ingångs match för att öka förstärkningen för en specifik transistor. Transistorn CGH60015D är utvecklad av Cree Inc. När den här transistorn stabiliseras förloras mycket av den tillgängliga förstärkningen. Det största problemet är att den inte kan levera hög förstärkning medan den är stabil. För att förbättra förstärkningen används en ingångsmatch som ska klara av två frekvens band och på sådant sätt öka gainet över dessa band. Arbetet täcker grunderna för att designa ett matchningsnätverk till en transistor, och hur man kan analysera kretsar mer ingående för att få en så realistisk simulering som möjligt. I detta projekt har ADS och modeller av GH60015D använts för att göra simuleringar av komponenter tänkta att tillverkas på ett glassubstrat. Det eftersökta resultatet av arbetet är att få ut så mycket storsignalsförstärkning som möjligt vid frekvenserna 2.11-2.17GHz och 2.62-2.69GHz. Resultatet av denna rapport visar metoder att bibehålla ovillkorligt utombandsstabilitet, medan man vid specifika band minskar stabilitetsmarginalen för att öka förstärkningen under kontrollerade villkor. Erhållen storsignalsförstärkning vid ungefär 15W uteffekt för de båda utvalda banden är ungefär 15.2 dB.
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Adiseno. "Design Aspects of Fully Integrated Multiband Multistandard Front-End Receivers." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3581.
Full textAbstract:
In this thesis, design aspects of fully integrated multibandmultistandard front-end receivers are investigated based onthree fundamental aspects: noise, linearity and operatingfrequency. System level studies were carried out to investigatethe effects of different modulation techniques, duplexing andmultiple access methods on the noise, linearity and selectivityperformance of the circuit. Based on these studies and thelow-cost consideration, zero-IF, low-IF and wideband-IFreceiver architectures are promising architectures. These havea common circuit topology in a direct connection between theLNA and the mixer, which has been explored in this work toimprove the overall RF-to-IF linearity. One front-end circuitapproach is used to achieve a low-cost solution, leading to anew multiband multistandard front-end receiver architecture.This architecture needs a circuit whose performance isadaptable due to different requirements specified in differentstandards, works across several RF-bands and uses a minimumamount ofexternal components.
Five new circuit topologies suitable for a front-endreceiver consisting of an LNA and mixer (low-noise converter orLNC) were developed. A dual-loop wide-band feedback techniquewas applied in all circuits investigated in this thesis. Threeof the circuits were implemented in 0.18 mm RF-CMOS and 25 GHzbipolar technologies. Measurement results of the circuitsconfirmed the correctness of the design approach.
The circuits were measured in several RF-bands, i.e. in the900 MHz, 1.8 GHz and 2.4 GHz bands, with S11 ranging from9.2 dB to17 dB. The circuits have a typicalperformance of 18-20 dB RF-to-IF gain, 3.5-4 dB DSB NF and upto +4.5 dBm IIP3. In addition, the circuit performance can beadjusted by varying the circuits first-stage biascurrent. The circuits may work at frequencies higher than 3GHz, as only 1.5 dB of attenuation is found at 3 GHz and nopeaking is noticed. In the CMOS circuit, the extrapolated gainat 5 GHz is about 15 dB which is consistent with the simulationresult. The die-area of each of the circuits is less than 1mm2.
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吳松軒. "Multiband Planar Antennas." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/91172014680560215948.
Full textAbstract:
碩士明新科技大學
電機工程研究所
98
Recently,there are rapid developments in wireless Communications.The frequency range covers 2-6GHz for Radio Frequency Identification (RFID 2.4GHz) , Wireless LAN (2400–2484 MHz,and 5150–5350/5725–5875 MHz MHz), Worldwide Interoperability for Microwave Access(WiMAX 3.5GHz) and Bluetooth(2.4GHz) and so on. In order to satisfy the IEEE 802.11WLAN standards and wimax application, the triple band operations of the printed antennas are required.A compact modified unilateral fed coplanar Waveguide antenna (CPW) designed by IE3D software is presented. The antennas are implemented on planar printed circuit boards (PCBs). These antennas are low profile, easy to be constructed and easy to be integrated with microwave integrated circuits. The thickness of the FR-4 PCB is 1.6mm. The size of the antenna is . The small broadband antenna (2265MHz~5895MHz) was constructed with same technique, The size of the antenna is also . This antenna is suitable for notebook application.
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YUEH, WANG CHUNG, and 王忠嶽. "Multiband Antenna Simulation and Design." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/34012930120670476862.
Full textAbstract:
碩士大葉大學
電信工程學系碩士在職專班
97
This thesis presents the design of two printed dipole antennas. These two antennas were developed to produce multiple resonant bands so as to support multi-standard wireless-communication products, such as laptop computers, personal digital assistances (PDAs), and mobile wireless networking devices. These standards include GSM 900 MHz (Global System for Mobile Communications; 870-960 MHz), DCS 1800 MHz (Digital Communication System; 1710-1880 MHz), PHS 1900 MHz (Personal Handy-Phone System; 1890-1915 MHz), WCDMA 2100 MHz (Wideband Code-Division Multiple Access; 2100-2170 MHz), WiFi 2.4 GHz (Wireless Local-Area Network; 2400-2483 MHz; also called WLAN), and WiMAX 2.6 GHz (Worldwide Interoperability for Microwave Access; 2.5-2.7 GHz). Note that the antennas presented here were originally designed for FarEastone telecommunications company (FET), for which the required GSM and DCS bands are in the ranges of 870-890 MHz and 1800-1880 MHz, respectively. For these two standards, the designed antennas must cover these two frequency bands, instead of 870-960 MHz and 1710-1880 MHz. For cost saving, the antennas were printed on FR4 substrates with a thickness of 1 mm. Numerical simulation was carried out using Zeland’s IE3D, a full-wave electromagnetic simulator. Before antenna prototypes were constructed and measured, the structural parameters of the designed antennas were varied iteratively until antenna performances are close to the required specifications. The first antenna type is a co-directionally meandered dipole antenna, in which the structures in the two arms of the antenna are almost symmetric with respect to the feeding point. The second antenna type is a bi-directionally meandered dipole antenna, in which the structures in the two arms are nearly anti-symmetric with respect to the feeding point. It is observed that the bi-directionally meandered dipole antenna is slightly more compact than the co-directionally meandered one.
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徐子祥. "Study of Multiband Bandpass Filter." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/68189032966925993169.
Full textAbstract:
碩士逢甲大學
通訊工程學系
101
In this paper, a multi-band filter as the research subject, are three small size, simple structure, and low cost bandpass filters, are applicable to wireless local area networks (WLAN) and the worldwide interoperability for microwave access (WiMAX). In addition to develop can be individually applied to GSM1800 (1.71-1.88 GHz) band in the four band pass filter, and implemented in 0.8 mm thickness, dielectric coefficient is 4.4 on the FR4 substrate. First introduced for dual-band bandpass filter, using twoλ/2 stepped impedance resonators to design, through the impedance change of stepped impedance resonators and the ratio of electrical length to adjust, the design frequency required band, the center frequency of the bandpass filter is 2.68 GHz and 5.27 GHz, the main size only 20.4 x 12.5 mm2. The experimental results show, the filter with WLAN (5200 MHz) and WiMAX (2700/5500 MHz) of the band. Next, a tri-band bandpass filter, the use of three asymmetric stepped-impedance resonators to design, the bandpass filter with the center frequency of three bands is 2.41 GHz, 3.6 GHZ, 5.86 GHz, the filter main size only 22.2 x 29.8 mm2. The experimental results show, the filter with WLAN (2400/5800 MHz) and WiMAX (2500/3500/5500MHz) of the band. Finally, a quad-band bandpass filter, the use of asymmetric stepped-impedance resonators to design, the quad-band bandpass filter architecture is divided into two parts, one part is designed to operate at the first and third passbands (1.85/3.75 GHz), the other part design and operation in the second and fourth passbands (2.75/5.25, GHz) by impedance adjusting asymmetric stepped-impedance resonator ratio and electrical length ratio, a four band pass filter can be designed, the experimental results show that, the filter with GSM1800 ( 1.71-1.88 GHz ), WLAN ( 5200 MHz ) and WiMAX ( 2700/3600MHz ) of the band. The three bandpass filter is proposed in this paper, the measurement and simulation are in good agreement, related to products can therefore be used for wireless communication.
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Chen, Wen-Wang, and 陳文旺. "Design of Multiband Operation Antenna." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/58373468536045029929.
Full textAbstract:
碩士高苑科技大學
電子工程研究所
98
The paper presents study of multi-band monopole antenna, which utilize simulation software Ansoft HFSS 10 to measure the antenna return loss which under -10dB with Smith chart and coincidence to the standard of range, and the multiband ( DVB、 GSM、GPS、DCS、PCS、Bluetooth、WLAN and WiMAX ) are contained and applied. The monopole antenna uses slot、meanderings、parasitic antenna、loop、reflecting board and “ PIFA ”, those techniques attempted to encourage each band effectively. Due to the design of antenna on the base, some slots are used the impedances of loops to compensate and close the impedances of resistors, also the meanderings is used to extension the length if antenna to fit the wavelength, parasitic antenna is used to gain the bandwidth in every each band, than this three prescriptions are inspired to lower noise interrupted at 1.6 GHz ~ 1.7 GHz、2.0 GHz ~ 2.2 GHz and 2.9 GHz ~ 3.2 GHz. At present, the laptop is miniaturization that ever, and the multiband monopole antenna could meet the requested. We will double the loop of antenna that we would use inside the limitation of space of laptop ,and it would be work by double the wave length, double the emerge between the frequencies of low-band and medium-band . The design of “ PIFA ” makes the bandwidth of high-band more wider, cause the Result of match of bandwidth between low-band and high-band is more than 25% ( above 500 MHz ) is fit the definition of Ultra Wide Band ( UWB ).
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韓政達. "Multiband Antennas Design and Implementation." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/11197892513355029743.
Full textAbstract:
碩士明新科技大學
電機工程研究所
97
Two types of antennas, loop antennas and CPW fed monopole antennas, are proposed and studied. The antennas are implemented on planar printed circuit boards(PCBs). These antennas are low profile, easy constructed and easy to be integrated with microwave integrated circuits. The implementation of antennas not only reduces the manufacturing cost but also decreases the antenna size and shrinks the size of the system further. In this thesis we implemented two kinds of antennas. One is a loop antenna, which is a double-band antenna for RFID usage. The other is a CPW fed antenna. By considering the feed of the antenna we design a new matching network to improve the return loss of the antenna. The frequency bands of the antenna are located on RFID、WLAN and WIMAX bands. The analysis and design of two antennas are simulated by using simulation software, IE3D and HFSS. The antennas are fabricated on single metal layered PCBs. The impedance of antennas is measured by using network analyzers. The radiation patterns and gain are measured in an anechoic chamber. Keywords: Loop antenna、CPW fed
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KUO, Chun-Yi, and 郭俊逸. "Design of Multiband Planar Antenna." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/94193761606288531922.
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Bakytbekov, Azamat. "Fully Printed 3D Cube Cantor Fractal Rectenna for Ambient RF Energy Harvesting Application." Thesis, 2017. http://hdl.handle.net/10754/626269.
Full textAbstract:
Internet of Things (IoT) is a new emerging paradigm which requires billions of wirelessly connected devices that communicate with each other in a complex radio-frequency (RF) environment. Considering the huge number of devices, recharging batteries or replacing them becomes impractical in real life. Therefore, harvesting ambient RF energy for powering IoT devices can be a practical solution to achieve self-charging operation.
The antenna for the RF energy harvesting application must work on multiple frequency bands (multiband or wideband) to capture as much power as possible from ambient; it should be compact and small in size so that it can be integrated with IoT devices; and it should be low cost, considering the huge number of devices.
This thesis presents a fully printed 3D cube Cantor fractal RF energy harvesting unit, which meets the above-mentioned criteria. The multiband Cantor fractal antenna has been designed and implemented on a package of rectifying circuits using additive manufacturing (combination of 3D inkjet printing of plastic substrate and 2D metallic screen printing of silver paste) for the first time for RF energy harvesting application. The antenna, which is in a Cantor fractal shape, is folded on five faces of a 3D cube where the bottom face accommodates rectifying circuit with matching network. The rectenna (rectifying antenna) harvests RF power from GSM900, GSM1800, and 3G at 2100 MHz frequency. Indoor and outdoor field tests of the RF energy harvester have been conducted in the IMPACT lab and the King Abdullah University of Science and Technology (KAUST) campus territory, and 252.4 mV of maximum output voltage is harvested.
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Chao, Chun-heng, and 趙君恒. "Study of multiband slot antenna designs." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/2gzp58.
Full textAbstract:
碩士逢甲大學
電機工程所
100
The thesis focuses on the design of slot antennas. Here, two slot antennas were proposed with different fed-techniques that allow the antennas to operate at different applications. A microstrip-fed slot antenna design for WLAN（2.4/5.2/5.8 GHz）application was initially proposed. In order to achieve dual-band operation, three slots were embedded into the ground plane that located beneath the microstrip feed-line. Two of the loaded slots were of step-impedance (SI) designs, and the third one was an inverted L-shaped slot. The proposed antenna exhibited 10-dB bandwidth of 607 MHz (24.78 %) and 1102 MHz (26.83 %) for the lower and upper operating bands, respectively. Besides demonstrating bi-directional radiation characteristic, steady gain variation and at least 66 % of efficiency were also measured. The second proposed antenna was a coplanar waveguide (CPW)-fed square-ring slot antenna with dual-band operation for WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.3/2.5/3.5/5.7 GHz) applications. The lower operating band was excited by the square-ring with asymmetric ground plane, and the upper operating band was induced by a stub-protruded monopole and a double-bent stub loaded into the ground plane. The antenna has small structure and exhibited bi-directional radiation characteristics. In addition, it also demonstrated steady gain variation within the WLAN and WiMAX operating bands.
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TIAN, CHANG-FU, and 田章甫. "Design of Multiband Planar Dipole Antenna." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9tuy5f.
Full textAbstract:
碩士明新科技大學
電機工程系碩士班
105
In this thesis, FR4 substrate and IE3D software are used to design multi-band antennas, including comb shaped with rectangular arm dipole antenna which can be applied to 1.8GHz,2.4GHz,2.45GHz and 2.6GHz frequency bands, comb shaped with needle arm dipole antenna which can be applied to 1.8GHz,2.4GHz,2.45GHz and 2.6GHz frequency bands, comb shaped with unequal rectangular arm dipole antenna which can be applied to 1.8GHz,2.4GHz,2.45GHz and 2.6GHz frequency bands , and comb shaped slot antenna which can be applied to 0.7GHz 0.9GHz and 1.8GH frequency bands. In this study, the size parameters of comb shaped planar dipole antenna are changed to observe the impacts on antenna characteristics. After simulation, the better parameter values of dipole antenna are obtained and can be used in GPS,RFID,WLAN and LTE frequency bands. The suitable size parameter L5=26.75mm of the comb shaped with uequal rectangular arm dipole antenna is obtained from simulated results. The proposed antenna can be used in RFID, WLAN and LTE frequency bands. The comb arm size parameters of the dipole slot antenna are adjusted to observe the variations with respect to the bandwidth, resonant frequency and gain of the proposed antenna. The better size parameters L5=29mm and L6=15mm are obtained to fabricate the comb dipole slot antenna which can be used in LTE 0.7GHz, LTE 0.9GHz and LTE 1.8GHz frequency bands. The proposed multiband dipole antennas by changing size parameters can be applied to GPS, WLAN, RFID and LTE frequency bands, respectively. Key words：planar dipole antenna、comb shaped rectangular arm、needle arm、WLAN、LTE
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Chen, Zhi-Ying, and 陳智穎. "Design of Printed Multiband LTE Antenna." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/u79ves.
Full textAbstract:
碩士元智大學
通訊工程學系
106
With the rapid development of cellular communication and higher quality demands by the customers, the communication system has evolved to the fourth generation. Supporting multiple frequency bands in different regions becomes a must for the modern smart phone. In this thesis, a multiband printed antenna for Long-Term-Evolution(LTE) is presented. The proposed antenna is based on a ultra-wide band (UWB) planar triangular monopole antenna (PTMA) and have a volume of 60×100×1.6〖mm〗^3. The size of a PTMA is first enlarged to cover the target LTE multiple bands and a mesh consisting of rectangular metal patch is applied to the additional space above the radiator. The orthogonal array (OA) method is employed to decide the distribution of these grids. Although the OA method doesn’t find the mesh distribution that will cover the LTE lowest band from 700MHz to 960MHz, but it does provide a initial mesh distribution that covers half of this band. Based on the initial pattern calculated by using OA, multiple current path approachs are used to meet the requirements of the lowest LTE band. With several modifications to further improve the impedance matching at higher frequence band, the final antenna is implemented. This S11 of the final antenna matchs the requirement of the LTE bands with two return losses. The bandwidth of the lower band is 262MHz(698-960MHz) with 6dB return loss and that of the higher band is 2590MHz(1410-4000MHz) with 10dB return loss. The measurements of the antenna in chamber, indoor, outdoor, and handled by hands are also presented in this study.
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Zeng, Jian-Hong, and 曾建弘. "Design of Multiband Planar MIMO Antenna." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/23593305021202076714.
Full textAbstract:
碩士龍華科技大學
電子工程系碩士班
102
This thesis presents a compact multiband planar MIMO antenna that covers the standards of the Global System for Mobile (GSM), Long Term Evolution (LTE) and Ultra-Wideband (UWB). The MIMO antenna contains two printed back-to-back multiband monopole elements with a closed distance of one-tenth wavelength of 900MHz. The element in the MIMO antenna is structured by merging an UWB antenna and a parasitic multi-loaded winding line monopole that is capable of providing the broadband coverage for the standards of the GSM, LTE and UWB. The size of the antenna element without ground plane was 30mm x 28mm. Because of the asymmetric element radiation pattern and, thus the MIMO antenna exhibits the desirable low mutual coupling effect at 900MHz frequency band. Further, a pair of meta-material resonator is constructed and placed between antenna elements in order to improve the correlation coefficient at 1.8GHz and 2.2GHz bands. The measured isolations of the prototype are less than -20 dB in all operating frequency bands.
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Hsu, Ming-Ren, and 許銘仁. "Multiband Chip Antennas for Mobile Handsets." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/3uaq95.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
96
In this thesis, the study mainly focuses on developing multiband chip antennas for mobile handsets. Three possible solutions and their extended and integrated designs are presented. By using the dielectric material as the chip base, the chip antenna can be smaller in size and simpler in design. Most of the applications of the traditional chip antennas are rarely used as the mobile phone antenna and are commonly designed with a single operating band to cover GPS or WLAN operation only. Different types of the antennas are proposed in the thesis. The metal patterns of the monopole and loop antennas are manufactured inside the chip base with an occupied volume of generally less than 0.8 cc, some even as small as 0.3 cc. Electronic components like the lens of the embedded camera and the speaker can be integrated close to the chip antenna with little influences on the radiation characteristics. Consequently, the developed chip antennas are suitable for mobile communications and can cover not only GSM850/900/1800/1900/ UMTS bands but also WLAN/WiMAX bands.
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FAN, CHIH-WEI, and 范智偉. "Design of Multiband Coplanar slot antenna." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/63944947429000173611.
Full textAbstract:
碩士明新科技大學
電機工程系碩士班
104
Coplanar slot antennas with three different shapes of radiator, comb, flag and polygon are designed in this thesis. Changing the element of comb radiator, the suitable size parameters are obtained from simulation. The simulated results are used to produce containing WLAN and LTE frequency bands antenna. Changing ground area of coplanar flag type radiator slot antenna is used to shift the impedance bandwidth to lower frequency. It can also be used to produce containing WLAN and LTE frequency bands antenna. Changing the bevel of polygonal radiator is used to get better size parameters. It can also be used to produce containing WLAN and LTE frequency bands antenna. In this thesis, the glass fiber (FR4) substrate is adopted to fabricate the antenna and IE3D electromagnetic simulation software is used for analyzing the designed antenna. The fabricated comb-radiator slot antenna can be applied to 1.8 / 2.4 / 2.6 / 3.6 GHz bands. The fabricated flag-radiator slot antenna can be applied to 0.7/0.9/1.8/2.4/2.6/3.6 GHz bands. The fabricated polygon-radiator slot antenna can be applied to 1.8 / 2.4 / 2.6 / 3.6 / 4.9 / 5 / 5.1 / 5.8 / 5.9 GHz bands. The obtained polygonal radiator coplanar slot antenna which peak gains are 2.31dBi, 3.76 dBi, 3 dBi, 3.31 dBi, 3.03 dBi, 3.04 dBi, 4.21 dBi, and 4.37 dBi at 1.8 GHz, 2.4 GHz, 2.6 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.8 GHz, and 5.9 GHz, respectively. Keywords: Long term evolution, Coplanar waveguide antenna, Comb-type radiator, Flag-type radiator, Polygonal radiator
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Hsieh, Yuan-pu, and 謝沅圃. "Multiband CPW-fed slot antenna design." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/10018352714300872868.
Full textAbstract:
碩士逢甲大學
電機工程所
98
The thesis focuses on the design of slot antennas and proposes a series of coplanar slot antennas with different structures by using a variety of design methods to meet different applicable frequencies. First, the thesis proposed a dualband coplanar triangle ring slot antenna. The lower band (2.34-2.8 GHz) is excited by the triangular ring slot and capacitive load, while the higher frequency band is excited by two T-slots embedded in the triangular radiation element, and its wide impedance bandwidth (5.15-6.9 GHz) is also due to the capacitive load. This novel antenna can be used in the WLAN 2.4/5.2/5.8 GHz. Then, a coplanar circular ring slot antenna design is proposed, and similar capacitive loading technique from the previous triangle ring slot antenna is used, so that the excited lower resonant mode can operate in the 2.4 GHz band. By inserting a pair of arc-shaped parasitic strip, a 5.8 GHz resonant mode is excited and by combining with the 4.5 GHz resonant mode, a broadband operation that covers the 5.2, 5.5 and 5.8 GHz bands is achieved. Besides demonstrating a bi-directional radiation characteristic, this antenna also shows steady gain variation in the WLAN 2.4/5.2/5.8 GHz operation. Finally, a coplanar rectangular slot antenna design is proposed for WLAN 2.4/5.2/5.8 GHz and WiMAX 2.6/3.5/5.5 GHz operations. The two wideband operations are excited by embedding two inverted L-shaped slot with dissimilar sizes into the rectangular radiating element. This novel antenna also shows steady gain variation in the WLAN and WiMAX operations.
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Cheng, Hung-Yu, and 鄭宏宇. "Design of a Multiband Low Noise Amplifier." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/63421168727165844576.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
96
In recent years, due to the emerging development of the wireless communication system, integrating many kinds of communication standards has become the newest trend. To meet the foregoing requirement, the multi-band receiver has been thus developed. Here, the design of the multi-band low-noise amplifier will become the key point of the RF front-end receiver. Based on the above background, this Thesis mainly focuses on the design of a multi-band low-noise amplifier (LNA). Its target frequency band is settled at 5.2 GHz, 2.4 GHz and 1.8 GHz. The designed LNA mainly employs the inductive degeneration technique and the transistor cascode circuit, in which the impedance matching circuit adopts a parallel LC resonance structure. Therefore, the power consumption of LNA is reduced significantly. In addition, for the simulation under the standard cells, both S11 and S22 for our proposed dual-band LNA can be -10 dB below. S21 is about 9.4 dB at 2.4GHz and about 12.3 dB at 5.2GH. NF is about 3.7dB at both 5.2GHz and 2.4GHz. Parameter P1dB is about -11 dBm ~ -14 dBm. IIP3 is about -1 dBm ~ -3 dBm. Its power consumption is about 7mW. Another design, the triple-band LNA (1.8 GHz, 2.4 GHz, 5.2 GHz), under ideal components is also presented. The performance is as follows: Both S11 and S22 can down to -10 dB below. S21 is about 15 dB ~17 dB. NF is about 1.1~1.8 dB. P1dB is about -12 dBm ~ -20 dBm. IIP3 is about -8 dBm ~ 1.5 dBm.
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Chen, Kuang-Chieh, and 陳光杰. "Multiband 3D Antennas for Wireless Mobile Communications." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/16044971730099756022.
Full textAbstract:
碩士逢甲大學
資訊電機工程碩士在職專班
99
The research goal of this thesis is to develop multiband 3D Antennas. We present two different 3D structure antennas which are developed by basing on the type of monopole antenna. The first antenna operating frequency bands were set to WiMAX (3.3 ~ 3.7GHz) and WLAN (5.15 ~ 5.35GHz, 5.725 ~ 5.825GHz). We used T-type monopole antenna to extend it. We initially built a planar antenna on a glass fiber substrate (FR4) which has a thickness of 0.8 mm, dielectric constant of εr = 4.4, and loss tangent of 0.022. Then, we created a dielectric cube of a volume of 18 × 2.5 × 0.8mm3 placed on the substrate to form a stereoscopic antenna. Finally, we use a metal sheet to round it. The structure can reduce the area of the antenna. We compare the radiation pattern, efficiency and return loss of 3D antenna with planar antenna. The second antenna is using the metal sheet to round a virtual cube. The volume is 12 × 15 × 6.5mm3. We can adjust the antenna’s structure and the shape of the metal sheet to control the operating frequency band, so that the antenna can operate at GSM (890 ~ 960MHz), DCS (1.71 ~ 1.88GHz), PCS (1.85 ~ 1.99GHz), UMTS (1.92 ~ 2.17GHz), WLAN (2.4 ~ 2.483GHz), and WIMAX (2.5 ~ 2.69GHz) band. We build this antenna on a glass fiber substrate (FR4). The thickness of the substrate is 1.6 mm. The antenna total size is 12 × 15 × 8.1mm3. The measured result shows that the return loss is better than 6dB in the desired frequency band. And the antenna’s radiation pattern is similar omni-directional. The results of measurement and simulation have good consistency.
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Pan, Po-Yu, and 潘柏宇. "Study of Multiband Monopole Antenna for LTE." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/3jrg8n.
Full textAbstract:
碩士義守大學
電機工程學系
102
Antenna device needs to be able to send and receive signals in wireless network communications. As technology advances, Mobile band from the early GSM 900/1800 (2G) and now widely used cellphone multimedia transmission UMTS 2100 (3G) and is developing LTE 700/900/1800/2600 (4G). This paper presents the multiband antennas applicable for LTE, this antenna have three- frequency band, the main design principles combined with G-type monopole antenna and L-type monopole antenna, with two different shapes monopole excitation frequency to complete. First, use of G-type monopole antenna structure resonance of 700MHz/1800MHz modal, then by adding L-shaped monopole antenna structure to increase the resonance path length, in addition to produce 2600MHz modal. The design frequency bands are for LTE 700/1800/2600. The simulator HFSS is employed for simulation and results show that 700/1800/2600MHz are included in the band.
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Wu, Chih-Hsien, and 吳致賢. "Multiband Hybrid Internal Antennas for Mobile Phones." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/4mnwra.
Full textAbstract:
博士國立中山大學
電機工程學系研究所
96
In this dissertation, a series of multiband hybrid mobile phone antennas, incorporating the electric-current and equivalent magnetic-current excitation mechanisms are presented. The design concept of the hybrid antenna is that the multiband operation is achieved by incorporating the resonant modes generated by the two above-mentioned excitation mechanisms. In the first and the second antenna designs, they are obtained by stacking the antennas using the electric-current and equivalent magnetic-current excitations, and both can achieve multiband operations. For the last two antenna designs, the two different excitation mechanisms can be incorporated on a single metal plate or dielectric substrate. This kind of hybrid are promising for application in bar-type and folder-type mobile phones. Besides, in order to pass some required testing criterions and analyze the environmental effects, the hybrid penta-band mobile phone antenna applied in bar-type and folder-type mobile phones is analyzed. The main topics include the speaker’s effects on the antenna’s performances, the analysis of user’s hand and head effects, and the analysis of the hearing aid compatibility.
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Hsu, Cho-Kang, and 許倬綱. "Composite Multiband Antennas for Portable Broadband Applications." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/13375863048703669637.
Full textAbstract:
博士國立交通大學
電信工程研究所
104
This dissertation is focused on the design of the novel compact antenna development for handset applications. These antenna designs have the merits of simple in geometry, easy for manufacture and integration, low cost, and exhibits good radiation efficiency. Firstly, the common multi-strip structure of monopole antennas was classified. A comparison of the advantages of multiple-strip design with merged modes, and identified the root cause of modes failing to merge are presented. Based on these observations, a half wavelength mode exists on dual-strip monopole antenna is found, in addition to the fundamental quarter wavelength modes. This half wavelength mode can facilitate mode combination. To explain the mutual coupling effect occurred between any two adjacent traces of the dual-strips monopole antenna for modes mergence, a conceptual equivalent circuit is proposed. This dissertation also provides a layout configuration for exciting the half wavelength mode to resolve the issues preventing non-merged modes from achieving a continuous impedance bandwidth and compact size in proximity to the ground. Hence, a ground proximity multiple-strip monopole antenna with 7mm no-ground area for mobile phones applications is developed. Besides, a small size forked shape multiple-strip monopole antenna with 86% impedance bandwidth is proposed for DVB reception and mobile services applications. Secondly, the material design of metal has become popular and increasingly important. However, the bandwidth and radiation efficiency of conventional antennas in handheld devices tend to decrease when the antenna is in proximity of metal or surrounded by a conducting edge, which affects the impedance matching considerably and renders restoring the performance by adjusting the antenna parameters difficult, examples of these include the monopole antenna, planar inverted-F antenna (PIFA), and inverted-F antennas (IFA); these antennas are widely used in handheld devices. Hence, a compact multi-band antenna is proposed for metal casing mobile phone applications. This structure can generate four resonance modes, including two slot modes and two monopole modes. The advantage of proposed structure is to obtain wide bandwidth (1700-4200MHz) on the high frequency to cover the mobile broadband services. Moreover, a compact dual-slot antenna is proposed for full metal rim application. The dual slots are designed for generating several resonance modes, including loop mode, slot mode, and monopole mode. Each slot can support resonance at low and high frequencies simultaneously achieving a wide impedance bandwidth. In addition, the practical situation is also considered. The energy absorbed from a handset by the human hand is a critical concern because it can alter the radiation pattern and cause considerable degradation of phone performance, particularly in a metal rim handset. The proposed inner slot prevents this issue. Finally, to address the dramatic increase in the demand for mobile broadband services and to support wider transmissions bandwidths of multiuser MIMO (MU-MIMO) and carrier aggregation (CA) functions that fulfill the extremely high data throughput requirements of devices, a multiband and wideband antenna with UWB feeding structure is proposed. This antenna is integrated the advantages of the UWB antenna at high frequency and the coupled-fed structure at low frequency. The proposed structure can obtain a wide bandwidth at low and high frequency to cover all of the handset broadband applications.