Dissertations / Theses on the topic 'Microwaves'
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Hopkins, Glenn Daniel. "Empirical characterization of a plated-through-hole interconnect for a multilayer stripline assembly at microwave frequencies." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15658.
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Daian, Mihai Stelian. "Thedevelopment and evaluation of new microwave equipment and its suitability for wood modification." Swinburne Research Bank, 2006. http://hdl.handle.net/1959.3/38305.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne, Faculty of Engineering and Industrial Sciences, 2006.[A thesis submitted for the degree of Doctor of Philosophy], Industrial Research Institute Swinburne, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2006. Typescript. Includes bibliographical references (p. 157-165)
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Matasane, Matasane Clement. "Investigation into the monitoring of microwaves in microwave cavities using optical techniques." Thesis, Peninsula Technikon, 2002. http://hdl.handle.net/20.500.11838/1076.
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Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2002.Tne purpose of this research or study was to perform an investigation in the use of optical fibers as sensor elements in order to develop a millimetre wave instrument capable of measuring microwave power within microwave cavities. Included in the scope of the project was an investigation of microwaves and microwave power measurements techniques. The emphasis of the research work was to develop expertise in photonics, by modeling and developing a measuring technique using optical techniques. This was deemed to be highly beneficial in laboratory experimentation and for possible use by microwave technicians. The implementation was amongst others, done by means of computer simulation and associated hardware, together with fiber-optic accessories. In order to conduct this research a literature and technology survey of current non-optical microwave power measurement technique was done. With this a review different power measurements systems and their relationship towards microwave power measurements was conducted. Within the scope of the project, a study of fiber optics sensors and its components was also conducted, which enabled models for a Mach-Zehnder microwave sensor to be developed. This resulted in the development of inexpensive electronic signal conditioning and detection techniques to enable measurements that employed a Mach-Zehnder Interferometer for this sensor technique. Finally, as microwaves are difficult to measure with pure electronic equipment, different approaches were made to investigate the temperature changes and other parameters on optical fiber to avoid damage to it. The specifications of hardware and circuitry suitable to measure these effects were determined.
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Zimmer, Aline Katharina. "Investigation of the impact of turbine blade geometry on near-field microwave blade tip time of arrival measurements." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26558.
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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jagoda, Jechiel; Committee Co-Chair: Jacobs, Laurence; Committee Member: Seitzman, Jerry. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ikiades, Aristidis Anthony. "Optical generation of microwaves." Thesis, University of Kent, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334037.
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Bienfait, Audrey. "Magnetic resonance with quantum microwaves." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS297/document.
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Dans une expérience classique de résonance paramagnétique électronique (RPE), le couplage entre les spins et leur environnement électromagnétique est faible, limitant considérablement la sensibilité de la mesure. Grâce à l’utilisation combinée d'un amplificateur paramétrique Josephson et de micro-résonateurs supraconductuers de hauts facteurs de qualité refroidis à quelques millikelvins, ce travail rapporte la conception et la mise en œuvre d’un spectromètre RPE dont la sensibilité de détection est limitée par les fluctuations quantiques du champ électromagnétique au lieu d’un bruit d’origine thermique ou technique. Des mesures de RPE pulsée sur un ensemble de doneurs Bismuth dans le silicium permettent de démontrer une sensibilité de 1700 spins détectés par écho de Hahn avec un signal-sur-bruit unitaire. La sensibilité est encore améliorée en générant un état de vide comprimé dans le guide d'onde de détection, ce qui réduit les fluctuations quantiques au-delà de la limite quantique. Les hauts facteurs de qualité et le petit volume de mode du résonateur supraconducteur développés pour une sensibilité accrue accroit également le couplage spin-résonateur jusqu'au point où les fluctuations quantiques ont un effet dramatique sur la dynamique des spins. En effet, l’émission spontanée de photons dans le résonateur micro-onde est considérablement renforcée par l'effet Purcell, ce qui en fait le mécanisme de relaxation de spin dominant. Le taux de relaxation est augmenté de trois ordres de grandeur lorsque les spins sont accordés à résonance, démontrant que la relaxation de spin peut-être contrôlée sur demande. Nos résultats fournissent une méthode nouvelle et universelle pour initialiser des systèmes de spin dans leur état fondamental, avec des applications en résonance magnétique et en information quantiqueIn usual electron-spin resonance (ESR) experiments, the coupling between spins and their electromagnetic environment is quite weak, severely limiting the sensitivity of the measurements. Using a Josephson parametric microwave amplifier combined with high-quality factor superconducting micro-resonators cooled at millikelvin temperatures, this work reports the design and implementation of an ESR setup where the detection sensitivity is limited by quantum fluctuations of the electromagnetic field instead of thermal or technical noise. Pulsed ESR measurements on an ensemble of Bismuth donors in Silicon spins demonstrate a sensitivity of 1700 spins within a single Hahn echo with unit signal-to-noise (SNR) ratio. The sensitivity of the setup is improved one step further by generating squeezed vacuum in the detection waveguide, reducing the amount of noise beyond the quantum limit. The high-quality factors and small mode volume superconducting microwave ESR resonator developed for enhanced sensitivity also enhances the spin-resonator coupling up to the point where quantum fluctuations have a dramatic effect on the spin dynamics. As a consequence, the spin spontaneous emission of microwave photons in the resonator is dramatically enhanced by the Purcell effect, making it the dominant spin relaxation mechanism. The relaxation rate is increased by three orders of magnitude when the spins are tuned to resonance, showing that spin relaxation can be engineered and controlled on-demand. Our results provide a novel and general way to initialize spin systems into their ground state, with applications in magnetic resonance and quantum information processing
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Antonio, Christian. "Characterisation and optimisation of the variable frequency microwave technique and its application to microfabrication." Australian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070220.122922/index.html.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted to the Industrial Research Institute Swinburne, Swinburne University of Technology in fulfillment of the requirements for the degree of Doctor of Philosophy - 2006. Typescript. Includes bibliographical references (p. 183-193).
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Kim, Jang-Yong. "Novel tantalate-niobate films for microwaves." Licentiate thesis, KTH, Microelectronics and Information Technology, IMIT, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-489.
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Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, and electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies.
Ferroelectric materials usually have high dielectric constants, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used in fabrication capacitors for electronic industry because of their high dielectric constants, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure, and electrically tunable microwave integrated circuits using ferroelectric thin films can be developed. Therefore, it is very important to characterize the dielectric constant and tunability of ferroelectric thin films.
This thesis shows experimental results for growth, crystalline properties and microwave characterization of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering of a stoichiometric, high density, ceramic NKN, ATN, BST target onto single crystal LaAlO3(LAO), Al2O3 (sapphire), and Nd:YAlO3, and amorphous glass substrates. By x-ray diffractometry, NKN, ATN, BST films on LAO substrates were found to grow epitaxially, whereas films on r-cut sapphire substrates were found to be preferentially (00l) oriented.
Coplanar waveguide interdigital capacitor (CPWIDC) structures were fabricated by standard photolithography processing and metal lift-off technique. Microwave properties of the NKN/Sapphire and ATN/Sapphire with CPW structures were characterized using on-wafer microwave measurement technique. Measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field through the connection between network analyzer and power supply was applied to measure voltage tunability. Measured S-parameter were used for the calculation of capacitance, loss tanδ, tunability and K-factor.
The NKN films interdigital capacitors with 2 μm finger gap on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ∼ 0.13, K-factor = tunability/tanδ from 152% @ 10GHz to 46% @ 40GHz.
The microwave performance of ATN film CPWIDC with 2 μm finger gap on sapphire substrate in the microwave range from 1 to 40 GHz showed that frequency dispersion is about 4.3%, voltage tunability was 4.7% @ 20GHz and 200 kV/cm, loss tangent ∼ 0.068 @ 20GHz, K-factor = tunability/tanδ is ranged from 124% @ 10GHz to 35% @ 40GHz.
The BST films CPWIDC with 2μmfinger gap on Al2O3 substrate showed frequency dispersion of capacitance in the microwave range from 1 to 40 GHz about 17%, voltage tunability = 1 - C(40V)/C(0) ∼ 22.2%, loss tangent ∼ 0.137 @ 20GHz, and K-factor = tunability/tanδ from 281% @ 10GHz to 95% @ 40GHz.
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Kim, Jang Yong. "Novel tantalate-niobate films for microwaves /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-489.
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Johansson, Jan. "Property predictions of wood using microwaves." Licentiate thesis, Luleå tekniska universitet, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16986.
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Internal properties of wood are an area of great interest in the worldwide wood industry. Higher demands on quality and productivity create needs for cheap and fast non-destructive methods for measuring the internal properties of wood. This work was carried out in order to investigate the possibility of using microwaves to predict the internal properties of sawn timber. The work consists of two parts. The first part has been to develop a scanner system based on a microwave camera (Satimo 9.4 GHz). The second part has been to develop prediction models for density, moisture content and strength properties of sawn timber using multivariate calibration. The primary result from this work is a well-functioning apparatus for microwave scanning of wood in a laboratory environment. The results also show that this technique is well suited to predicting density and moisture content of sawn timber and has a potential for strength property measurements.Godkänd; 2001; 20070314 (ysko)
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Shafer, Floyd L. (Floyd Lorenz). "Interaction of Microwaves and Germinating Seeds." Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc331641/.
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This investigation was concerned with determining the interaction of microwaves with germinating seeds. This study covers two different approaches. The preliminary efforts covered the response of germinating seeds to treatment by microwaves and heat. The second phase of the investigation used microwaves as a probe to determine some of the processes of early seed germination.
The preliminary investigation measured the internal metabolic process by ATP production. Leakage of ions and organic material from germinating seeds indicated that membranes are a target of microwaves and heat. Electron photo-micrographs showed an increase in damage to membranes as heat and microwave treatments were increased.
The second phase of this investigation was concerned with determining some of the biological activity at the initiation of germination of wheat seeds, Triticum aestivum L., using a resonating microwave cavity oscillating at 9.3 GHz as a probe. Direct current conductivity measurements were also made on the seeds as a means of confirming the observations made with the microwave cavity.
There was no observable difference between treatment by UHF or heat in the ultrastructure of germinating seeds. A dielectric response far above that of free water was found as live seeds of wheat began to imbibe water. This effect was assumed to be due to the release of ions, because conductivity increased as corresponding quantities of water were imbibed; and both conductivity and dielectric response decreased as imbibition progressed. Although dead seeds also imbibe water, they do not show this decrease in dielectric response. The dielectric response of live seeds was reduced after the initial imbibition, showing that water became tightly bound as imbibition progressed.
The dielectric response of actively growing shoots from the seeds was much less than that of the seeds themselves. The large quantity of water in the shoots is assumed to be immobile, being tightly bound within the membranes, enzymes, and organelles.
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Cullen, Lorri Denise. "Factors affecting heating of calzones in microwaves." Thesis, Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3945.
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Santorelli, Adam. "Breast screening with custom-shaped pulsed microwaves." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107686.
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Microwave imaging has been proposed as a possible complimentary imaging technique to X-ray mammography for early-stage breast cancer detection and screening. Based on the intrinsic differences in the various tissues of the breast at microwave frequencies, microwave imaging offers an imaging modality that is safe, pain-free, and without limitations on the frequency of the exam.An initial time domain microwave imaging system has been previously developed within our group. Accurate numerical models, for finite-difference time-domain simulations, matched to the experimental system have been developed. Numerical simulations are used to assess the safety of the microwave imaging technique. We calculate the maximum energy absorbed by the breast when exposed to incident microwaves and ensure that these values fall within the established thresholds.In this thesis we will test our hypothesis that an augmented microwave imaging system can improve tumour detection by making use of custom-made pulses with critical frequency content. We integrate passive microwave circuitry with a previously designed experimental microwave imaging system in order to create a new system that transmits an optimized pulse. We contrast measurement results of this newly developed system with those of the previously developed experimental system when imaging various tissue phantoms.L'imagerie micro-ondes a été proposée comme une nouvelle technique pour la détection du cancer du sein qui est complémentaire au mammographie. Cette technique est basée sur les differences intrinsèques des tissus mammaires différents à des frequences micro-ondes. L'imagerie mirco-onde est une technique qui est sûr, sans douleur, et sans limitations sur la fréquence de l'examen.Un système préliminaire pour l'imagerie micro-ondes dans le domaine temporel a déjà été mis au point. Des modèles numériques précis , pour les simulations avec la "finite-difference time-domain" technique, qui sont en accorde avec la système expérimental sont construit.Des simulations sont utilisé pour évaluer la sécurité de la technique d'imagerie micro-ondes. Nous calculons le maximum d'énergie absorbée par le sein quand il est exposé aux micro-ondes incidentes et nous s'assure que les résultats sont en accord avec les normes établis. Dans cette thèse, nous allons tester notre hypothèse que un système d'imagerie micro-ondes augmentée peut améliorer la détection des cancers en utilisant des impulsions fait sur-mesure. Nous utilisons des circuits micro-ondes passives, avec le système déjà développé, pour créer un nouveau système qui transmet un impulsion optimisé. On compare les résultats de nos mesures avec les deux systèmes quand on utilise des fantômes de tissus divers.
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Horwitz, Paul. "Use of microwaves for skin lesion treatment." Thesis, Bangor University, 2017. https://research.bangor.ac.uk/portal/en/theses/use-of-microwaves-for-skin-lesion-treatment(dffef713-520f-42ed-a1e7-93ba9e24d902).html.
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Against a backdrop of rising incidence of Non-Melanoma Skin Cancer, substantial previous work has resulted in a 14.5GHz Microwave Applicator that ablates small areas of dermal tissue. This previous work has highlighted the need for improvements in uniformity and the estimation and control of heating dosage. The aim of this work was to improve heating uniformity and control by numerically modelling the thermal characteristics of the existing Microwave Applicator and so gauge the effects of direct thermal feedback, surface cooling, temperature bias and small uncertainties in power delivery to the time and depth of ablation and so provide a guide to thermal dosage and maximum ablation depths achievable for 5.8GHz, 14.5GHz and 24.125GHz; and to produce a simple Electromagnetic numerical Model to identify methods of improving the uniformity of the heating profile at 14.5GHz. And finally, to use these results to guide the design of a New Microwave Applicator using a commercial modeller (CST Design Studio).This New Microwave Applicator operating at 14.5GHz incorporates an integral thermal camera viewing the target tissue which provides direct thermal feedback during the ablation process which is used to control the power delivery. The new mechanical construction incorporates PTFE side sections to flatten the heating profile.
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Regmi, A. (Ankit). "Reflection measurement of building materials at microwaves." Master's thesis, University of Oulu, 2017. http://jultika.oulu.fi/Record/nbnfioulu-201701141092.
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Abstract. Radio waves interact differently with different materials. The knowledge of reflection and transmission characteristics of the electromagnetic waves through and from the building walls is the key in designing a radio propagation model. The dielectric properties of the material determine the behavior of reflection and transmission of the electromagnetic waves. Therefore, an oblique reflection model is implemented in this thesis to estimate the dielectric properties of various walls at frequency range of 0.7–7 GHz (6.3 GHz bandwidth). The measurement setup consists of a four-port vector network analyzer, two wideband dual-polarized cross-shaped Vivaldi antennas and two 8 m long coaxial cables. Measurements for parallel and perpendicular polarizations are achieved simultaneously by using the dual-polarized antennas. Time-domain gating is applied to separate the desired reflection and eliminate all other multiple reflections from the environment and to suppress the Line-of-Sight component from the delayed response.
The estimation of dielectric property of a material is an optimization problem where a suitable objective function is minimized to get the appropriate value. A theoretical model is implemented, so that the minimum difference between the theoretical and measured absolute value of reflection coefficient gives an estimated value of complex relative permittivity. The non-linear least squares algorithm is used for optimization purpose. The real and imaginary part of complex relative permittivity is investigated in this thesis. The real part signifies the amount of electric energy stored in a material, and is called dielectric constant whereas the imaginary part is called the loss factor, which signifies the dissipation of the radiated energy. The estimated values are in good agreement with the values found in the literature. The estimated dielectric properties in this study, such as dielectric constant, loss tangent and Brewster angle of the various materials can be utilized further in designing radio propagation models for similar environments.
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CASU, SERGIO. "Innovative ISM and Diagnostic Applications of Microwaves." Doctoral thesis, Università degli Studi di Cagliari, 2019. http://hdl.handle.net/11584/260389.
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The widest employment of electromagnetic (EM) waves is probably in the telecommunication
area. Nevertheless, the potential of electromagnetism goes beyond telecommunication
and can find application in a variety of fields. Structures such as antennas and
resonant cavities allow the generation of well-known EM fields that is possible to use in a
controlled way. In this thesis, different uses of EM field are proposed, involving different
areas. As a high power application, in the agriculture sector, a model to evaluate the
feasibility of using EM waves to disinfect the superficial layer of the soil is presented. The
variation of the dielectric constant due to the raise in temperature is taken into account
and power and time of irradiation to obtain the desired profile of temperature of the soil
is determined. A medium power application uses a resonant cavity as a (temperature)
controlled environment in which an enzymatic reaction takes place in an aqueous solution.
The yield of the reaction is compared with the yield obtained using conventional
heating. As a low power application, healthcare sector is considered, and the design of
an array of coil on a flexible substrate for magnetic resonance is presented. Furthermore,
a numerical evaluation of the EM field, inside a full blood bag, is carried out, to compare
it with the EM field generated by an RFID reader intended to be used for identification
of blood bags.
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Imholt, Timothy James. "Carbon Nanotube/Microwave Interactions and Applications to Hydrogen Fuel Cells." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc5796/.
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One of the leading problems that will be carried into the 21st century is that of alternative fuels to get our planet away from the consumption of fossil fuels. There has been a growing interest in the use of nanotechnology to somehow aid in this progression. There are several unanswered questions in how to do this. It is known that carbon nanotubes will store hydrogen but it is unclear how to increase that storage capacity and how to remove this hydrogen fuel once stored. This document offers some answers to these questions. It is possible to implant more hydrogen in a nanotube sample using a technique of ion implantation at energy levels ~50keV and below. This, accompanied with the rapid removal of that stored hydrogen through the application of a microwave field, proves to be one promising avenue to solve these two unanswered questions.
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Dolan, James P. "Microwave freeze-drying of aqueous solutions." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12052009-020317/.
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Malyshev, Dmitry. "Disruption of bacterial spores using microwaves and nanoparticles." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/120065/.
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This thesis shows how microwaves and nanoparticles can be used to enhance the disruption of spores in the context of a novel microwave-based bacterial detector. Infections linked to Clostridium difficile are a significant cause of suffering. In hospitals, the organism is primarily acquired through the faecal-oral route as spores excreted by infected patients contaminate the healthcare environment. Microwave-based spore disruption is the focus of this project offers a potential rapid diagnostic method to detect spores, including C. difficile spores by making them release DNA which is then detected. One of the limiting factors of this method was the power required and it was hypothesised that by using a new microwave cavity and adding nanoparticles, the DNA release from spores can be achieved with less power. First, the spore surface properties of the different isolates of C. difficile were compared. A significant variation in both spore morphology and spore hydrophobicity of clinical isolates of C. difficile was observed. In particular, the "pineapple-like" shape of strains was associated with higher hydrophobicity in spores, while the loose outer exosporium layer was associated with lower hydrophobicity. The isolates were then tested for DNA release in response to microwaving. Spores were shown to release single-stranded, but no double stranded DNA. The spores were also not visibly changed by microwave exposure, suggesting a non-destructive mechanism of disruption. To study this mechanism further, the microwave system was updated to remove overall sample heating and tested under electric fields, magnetic fields and a combination of the two. The electric field was shown to be causing the disruption of spores, field showed a positive correlation with increasing disruption. Finally, the spores with tested with microwaves and nanoparticles, where nanoparticles showed a significant improvement in two of the four tested isolates. A computer model of the spore and nanoparticle interactions was made, which offered a plausible mechanism for the nature of microwave mediated disruption and the improvement in disruption caused by nanoparticles.
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Parsa, Nitin. "Non Linear Interaction of Microwaves with Ferroelectric Materials." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1451999954.
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Jayatissa, Thilini. "Expediting the Consolidation of Clayey Soils Utilizing Microwaves." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7310.
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Post-construction settlement has been an issue in the field of construction due to the excessive time taken for the dissipation of pore water pressure. This is significant for construction carried out on clayey soils primarily due to the low permeability of clayey soils. Therefore, attention has been directed at finding means of increasing the rate of pre-consolidation. Recent research has focused on the effects of temperature on consolidation. It has been shown that elevated temperature increases the hydraulic conductivity of pore water due to both the reduction of viscosity and differential volumetric expansion of soil and water. This results in an increase in the rate of pore pressure dissipation. In addition, it has been proven that compressibility properties also improved at elevated temperature and subsequently, the rate of consolidation of the clay. This research aimed to study the feasibility of utilizing microwaves to expedite the aforementioned temperature elevation and the subsequent consolidation of a clay soil. A numerical model has been formulated using finite difference methods to theoretically predict the temperature rise and pore pressure dissipation. The results of the numerical model proved to be in general agreement with the experimental data. The feasibility of utilizing microwaves to raise the temperature of the soil sample was also evaluated practically by conducting bench-scale experiments. The use of microwave irradiation to rapidly increase the temperature of saturated clay was quantified by this research and was proven to be more efficient than currently used soil heating methodologies. Comparable consolidation experiments showed that increasing the temperature of the sample using microwave heating resulted in a higher rate of settlement when compared with the settlement of the non-heated sample while the ultimate percentage settlement of both were equal.
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Jakku, E. (Eino). "Evaluation of methods to simulate the properties of stripline structures." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514271890.
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A stripline structure is closed and therefore protected against surrounding EMI and it is easy to bury in multiplayer structures, which offer higher circuit density. This thesis focuses on the evaluation (and verification via actual structures) of the correct simulation of striplines and, as a new aspect, the advantages of using a dual-stripline. Multiple design methods and electromagnetic simulation systems were tested and properties of these are compared.
For a reliable design it is still necessary to use at least two tools, at first a very fast tool having excellent circuit parameter optimization methods and then some electromagnetic simulator, which can be used to the complete the realizable layout. That is, because all the electromagnetic simulators suffer from the same limiting factors, the memory capacity of the computer and the unacceptable calculation time.
It has been discovered through modelling that the "cat-eye" shape having many more and larger local inaccuracies at the thinned edge areas of the sintered conductor in LTCC structures increases the conductor losses. Therefore it is important to develop new manufacturing methods capable of producing better-shaped conductors.
A combination of broadside coupled parallel connected striplines has been tested both in High Temperature Superconducting ( HTS ) and LTCC materials. A two-conductor stripline, a dual stripline, raises the power handling capability of a microwave bandpass HTS filter. In addition, it offers the possibility to use a normal metal protection layer at the surface of the superconductor without degradation of electrical properties, thus increasing the power handling capability even more. The dual stripline solution in LTCC would offer some preferable properties in high power filters only.
The shape of the ground plane used for trimming the coupling between resonators was also found to have a remarkable influence on the quality factor of the resonator. A quite narrow ground strip can offer a much better quality factor with the same coupling level than a meshed or continuous ground plane, but it requires accurate design and manufacturing methods. It would help to design filters with lower loss in the passband without compromises in the attenuation outside the passband.
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Jordan, Jennifer L. "Contactless Radio Frequency Probes for High Temperature Characterization of Microwave Integrated Circuits." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1402066531.
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Havlíčková, Klára. "Design přístroje pro mikrovlnnou diatermii." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382620.
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My thesis is focused on design of a microwave diathermy therapeutic machine. Its main goal is to improve a shape, technical solution, ergonomics and visual aspects of nowadays microwave diathermy machines and to innovate this part of technology, ergonomics, economics and the usage of this device on the field of physiotherapeutical care.
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Yi, Changhyun. "InP-based heterojunction bipolar transistors for high speed and RF power applications : advanced emitter-base designs." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13083.
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Lin, Kuan-ting. "Site-diversity attenuation measurements at 28 GHz by radiometers for an earth-space path /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265143147216.
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Moriyama, Takahiro. "Nonlocal and local magnetization dynamics excited by an RF magnetic field in magnetic multilayers." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 152 p, 2009. http://proquest.umi.com/pqdweb?did=1650511361&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Zhou, Lin. "Simulations of emissivity in passive microwave remote sensing with 3-dimensional numerical solutions of Maxwell equations and fast algorithm /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5986.
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Ku, Harry, and ku@usq edu au. "High energy rate of joining thermoplastic composites using microwaves." Swinburne University of Technology, 2000. http://adt.lib.swin.edu.au./public/adt-VSWT20050418.140632.
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One of the most important areas of the application of industrial microwave technology for materials processing is curing polymers and polymer based composites, and this is currently in a state of considerable flux. Curing of thermosetting composites in multi-mode applicators and joining of a range of thermoplastics in ridged waveguides have been some of the major achievements in the field. This research extends the applications horizon of microwaves in the area of random fibre reinforced thermoplastic composites joining and places emphasis on the development of facilities and methodologies aiming at maximising bond quality. It discusses the fixed frequency microwave equipment used, including a 0.8 kW variable control power generator operating at 2.45 GHz, waveguide and a tuning piston designed for obtaining a standing wave at the seam of the butted and lapped test pieces. The effect of power input and cycle time is detailed together with the underlying principles of test piece material interactions with the electromagnetic field. The process of heterogenous joining, with filler material, or primer, of 33% by weight of random glass fibre reinforced nylon 66, polystyrene (PS) and low density polyethylene (LDPE), thermoplastic composites is mentioned together with the process of autogenous joining of 33% by weight of random carbon fibre reinforced polystyrene (PS) and low density polyethylene (LDPE). The weldability dependence on the dielectric constant, dielectric loss, and hence loss tangent of these materials is also described and investigated. Measurements of the dielectric properties were carried out using the waveguide transmission, probe kit and resonant cavity techniques. X-ray photoelectron spectroscopy for surface analysis was carried out to assess if the filler material had diffused into the parent thermoplastic composite materials. Bond strength measurements of the welded thermoplastic composites were obtained using tensile shear tests. A variable frequency microwave (VFM) facility was also used to join the thermoplastic composites and bond strength results obtained were compared with those procured by the fixed frequency microwave configuration.
From the measured data of LDPE/GF (33%), PS/GF (33%) and nylon 66/GF (33%), it was found that at relatively high temperatures and frequencies, these materials became less reflective and permitted more microwave energy to be absorbed. At the same time, their dielectric loss factor increased with temperature and frequency and enabled more of the absorbed energy to be converted to heat. Therefore, within limits, higher temperatures and higher frequencies were more suitable for microwave-assisted joining of the three materials tested. As to the primer/filler, only liquid rapid Araldite was found to be the most favourable in microwave-assisted joining of fibre reinforced thermoplastic (FRTP) composites because of its considerably high value of loss tangent. Another important finding was that the dielectric probe method was found to be the recommended technique to use for measurements of �ՄS and tan �� in microwave joining of materials out of all the methods applied. However, for low loss materials, the values of tan �� need to be acquired through the resonance cavity method.
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Bool, Christopher J. "The application of microwaves to some heterogeneously catalysed reactions." Thesis, University of Hull, 1997. http://hydra.hull.ac.uk/resources/hull:12765.
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Three heterogeneously catalysed reactions have been investigated using both conventional and microwave heating of the catalyst bed. The oxidative coupling of methane reaction has been widely studied using conventional methods of catalyst heating but only limited works have investigated the continuous microwave heating of catalysts. This research compares the two methods of catalyst heating in detail. Catalysts based on rare - earth oxides and chloride containing materials were studied. The combustion of methane reaction has also been studied under microwave and conventional heating methods. The reaction has attracted some attention in recent years with the increasing research in the area of natural gas powered vehicles. Emission regulations for the automotive industry are becoming increasingly stringent and the clean up of exhaust emissions from natural gas vehicles is of increasing interest. For both of the above reactions, the microwave heated example occurred at lower bulk temperatures than the conventionally heated reaction. However, documented equilibrium constant calculations show that the actual reaction temperature was far in excess of the observed bulk temperature. It is therefore postulated that there exist within the catalyst bed small areas which are at elevated temperature relative to the observed bulk temperature. Such areas are thought to be where the reaction actually occurs and have been termed "hot spots".
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Cardona, Amengual Javier. "Molecular simulations of the interaction of microwaves with fluids." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27631.
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The interaction of electromagnetic radiation with matter has led to a large number of interesting applications. The propagation of electromagnetic waves within materials is described by Maxwell’s equations. However, the fundamental understanding of the causes of the response of the material, defined by constitutive relations for its complex, frequency-dependent dielectric constant, can only be achieved through the study of processes occurring at the molecular scale. The fluctuation-dissipation theorem relates the frequency-dependent dielectric constant of a material to equilibrium fluctuations in its dipole moment. This fact can be used to determine dielectric properties from equilibrium molecular dynamics simulations for frequencies covering the microwave region of the electromagnetic spectrum (300 MHz – 300 GHz). In this work, the ability of current force fields to predict dielectric spectra of one component systems and mixtures is examined, showing accurate results when compared with experimental data for the systems under consideration. Additionally, the influence of temperature on the dielectric spectra is analysed, yielding equally satisfactory results. In the particular case of ethanol/water mixtures, the estimation of dielectric spectra at intermediate concentrations using molecular dynamics simulations outperforms the traditional use of mixing rules. The simulations of these systems reveal the importance of collaborative processes between groups of molecules, such as hydrogen bond networks, in the overall dielectric response. The reduction of the contribution of these processes as temperature increases confirms the weakening of these networks at high temperatures. The predicted dielectric properties are used in a heating model to estimate temperature profiles in microwave heating processes. Unexpected results are obtained which reveal the need for accurate determination of the electric field distribution within the workload in order to obtain representative heating profiles. In contrast, penetration depths are accurately determined from dielectric properties generated through molecular simulations.
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Lynch, Matthew Earl. "The Effect of Microwaves on Aqueous Corrosion of Glass." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34187.
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Glass corrodes in aqueous environments. The corrosion process is well-understood for many circumstances involving long periods of time at room temperature as well as processes that involve conventional heating, but the effect of microwave energy on glass corrosion has never been fully investigated. It was suspected that microwaves may alter or accelerate the aqueous corrosion processes that occur in glass which contribute to migration into foods or other materials. Lithium disilicate (Li2O-2SiO2) and commercial soda-lime glass were corroded using both conventional and microwave heating in this study. The results did not clearly show substantial differences in corrosion under the test conditions, but leave open the possibility of an altered mechanism in some circumstances. These findings suggest the need for testing at a lower microwave frequency, specifically 2.45 GHz.Master of Science
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Lynch, Matthew. "The Effect of Microwaves on Aqueous Corrosion of Glass." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/34187.
Full textAbstract:
Glass corrodes in aqueous environments. The corrosion process is well-understood for many circumstances involving long periods of time at room temperature as well as processes that involve conventional heating, but the effect of microwave energy on glass corrosion has never been fully investigated. It was suspected that microwaves may alter or accelerate the aqueous corrosion processes that occur in glass which contribute to migration into foods or other materials. Lithium disilicate (Li2O-2SiO2) and commercial soda-lime glass were corroded using both conventional and microwave heating in this study. The results did not clearly show substantial differences in corrosion under the test conditions, but leave open the possibility of an altered mechanism in some circumstances. These findings suggest the need for testing at a lower microwave frequency, specifically 2.45 GHz.Master of Science
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Salazar, Garza Gustavo Adolfo. "Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011818/.
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The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl]-N,N-diethylbenzenamine are reported. The employment of microwaves in the preparation of 1 decreased the reaction time from 48 to 2 hours compared to the conventional reflux method. Stoichiometry variations allows for selective preparation of either a mononuclear, 1, or binuclear, fac-[Re2Cl2(CO)6], 2, complex. The photophysical properties of 1 were analyzed finding that it possesses significant luminescence rigidochromism. The steady state photoluminescence emission spectra of 1 in solution shift from 550 nm in frozen media to 610 nm when the matrix becomes fluid. Moreover, a very sensitive emission spectral analysis of 0.1 K temperatures steps shows a smooth transition through the glass transition temperature of the solvent host. Furthermore, synthetic modifications to L have attained a family of ambipolar compounds that have tunable photophysical, thermophysical and other material properties that render them promising candidates for potential applications in organic electronics and/or sensors - either as is or for their future complexes with various transition metals and lanthanides.
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Devaraj, Kiruthika. "The centimeter- and millimeter-wavelength ammonia absorption spectra under jovian conditions." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42806.
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Accurate knowledge of the centimeter- and millimeter-wavelength absorptivity of ammonia is necessary for the interpretation of the emission spectra of the jovian planets. The objective of this research has been to advance the understanding of the centimeter- and millimeter-wavelength opacity spectra of ammonia under jovian conditions using a combination of laboratory measurements and theoretical formulations. As part of this research, over 1000 laboratory measurements of the 2-4 mm-wavelength properties of ammonia under simulated upper and middle tropospheric conditions of the jovian planets, and approximately 1200 laboratory measurements of the 5-20 cm-wavelength properties of ammonia under simulated deep tropospheric conditions of the jovian planets have been performed. Using these and pre-existing measurements, a consistent mathematical formalism has been developed to reconcile the centimeter- and millimeter-wavelength opacity spectra of ammonia. This formalism can be used to estimate the opacity of ammonia in a hydrogen/helium atmosphere in the centimeter-wavelength range at pressures up to 100 bar and temperatures in the 200 to 500 K range and in the millimeter-wavelength range at pressures up to 3 bar and temperatures in the 200 to 300 K range. In addition, a preliminary investigation of the influence of water vapor on the centimeter-wavelength ammonia absorptivity spectra has been conducted. This work addresses the areas of high-sensitivity centimeter- and millimeter-wavelength laboratory measurements, and planetary science, and contributes to the body of knowledge that provides clues into the origin of our solar system. The laboratory measurements and the model developed as part of this doctoral research work can be used for interpreting the emission spectra of jovian atmospheres obtained from ground-based and spacecraft-based observations. The results of the high-pressure ammonia opacity measurements will also be used to support the interpretation of the microwave radiometer (MWR) measurements on board the NASA Juno spacecraft at Jupiter.
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Möller, Cecilia. "Design and Experiments with High Power Microwave Sources : The Virtual Cathode Oscillator." Doctoral thesis, KTH, Rymd- och plasmafysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104794.
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High-Power Microwaves (HPM) can be used to intentionally disturb or destroy electronic equipment at a distance by inducing high voltages and currents.This thesis presents results from simulations and experiments with a narrow band HPM source, the vircator. The high voltages needed to generate HPM puts the vircator under great stress, especially the electrode materials. Several electrode materials have been tested for endurance and their influence on the characteristics of the microwave pulse. With the proper materials the shot-to-shot variations are small and the geometry can be optimized in terms of e.g. output power or frequency content. Experiments with a resonant cavity added to the vircator geometry showed that with proper tuning of the cavity, the frequency content of the microwave radiation is very narrow banded and in this case the highest fields are generated. The vircator can be built in different geometries. Four different vircator types are investigated and the coaxial vircator is found to have advantages as a high radiated power and the possibility to vary the polarization during operation.Since HPM pulses are very short and have high field strengths, special field probes are needed. An HPM pulse may shift in frequency during the pulse and therefore it is very important to be able to compensate for the frequency dependence of the entire measurement system. The development and use of a far-field measurement system is described.QC 20121122
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Smit, Johannes Petrus. "Model for microwave absorption and heat transfer in a combination washer dryer / by J.P. Smit." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9697.
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The work presented within this dissertation focusses on the development of affinite element method (FEM) model for the microwave absorption and heat transfer within a microwave combination washer dryer (MCWD). FEM will be used to aid in the implementation of more advanced fluid dynamics such as laminar or turbulent flow, that may be present within the system. The intended use of the model is to aid a South African based company in the development of a control system for the MCWD. The model development presented focusses on the washing cycle of the MCWD and will therefore not take into account the drying cycle of the system. The target of the microwave heating within the model will be distilled water as the dielectric constant of water is a know quantity.
Various literature sources on microwave absorption and heat transfer models can be found, but none specific to the topic of the combination washer dryer. By reviewing literature from various sources, the finite element method was selected as the modelling technique and the COMSOL® software package was selected as the tool for developing the model.
A model for the MCWD will be developed within the COMSOL® environment which in turn implements FEM as a technique to solve the model. The model development is broken into nine stages. Stage one start by modelling the heat transfer within the washing drum. Each consecutive stage expands the model by adding features or model domains. Model verification takes place in parallel to the development by verifying each stage before moving to the next stage. The stage eight and nine models, which represent a full three dimensional model of the system, are selected to be validated as the final models. Stage eight models the system without an enclosure and makes use of convective cooling boundary conditions on the boundary of the air enclosed within the system enclosure. Stage stage nine models the system with the aluminium enclosure of the system and also implements convective cooling boundary conditions on the outer boundary of the aluminium. The boundary between the enclosed air and aluminium enclosure is implemented as a normal convective heat transfer boundary between a gas and solid.
Data capturing is done using the dSpace® platform. Sensors to log the microwave power and system temperature are selected and optimal placement of the sensors is evaluated. The capturing platform is interfaced to the sensors by an in-house developed signal conditioning board.
Model validation is completed by comparing the response of the model to the practical system. Numerous simulations are completed to select the optimal configuration of the model that provides the optimal response.
The stage eight model was found to be more accurate then the stage nine model with respect to the difference between the simulated and expected response over the whole domain of the transient temperature response. A further method implemented to easily compare the results of various simulations is by comparing the average absolute temperature of the response over the whole domain of the transient response. The average absolute temperature is calculated by taking absolute difference between the expected results and the model response at each time step within the response domain and then to average the absolute difference. This enables the comparison of two responses using two values. Needles to say this method should not be used alone and should be used in conjunction with a comparison over the full response domain. Use of the average absolute temperature difference is aimed at filtering the results from a selection of results which warrants a more in depth investigation. Using a comparison of the average absolute temperature difference of the target in the 500 W model, it was found that their respective values are 2:92 °C and 11:36 °C. The stage eight model computation time was far less than the stage nine model and is therefore recommended for further development.
The final conclusion was made that the stage eight model represents the system fairly accurately at this stage and warrants further development by expanding the model to account for the drying cycle of the MCWD. The term fairy accurate is used to describe the results as further improvement of the model is definitely possible with regards to the accuracy of the transient response of the system. Further improvement of the model response may be possible by implementing a smaller mesh size or launching an in depth study on the effect of the various material thermal properties on the response of the system during various stages. For instance below a certain temperature the response closely represents the expected response and above that temperature the response various greatly from the expected response.
Future work on the model include, to change the target from distilled water to an actual representation of the textiles intended to be washed within the MCWD. This will require a study into how the various parameters such as the density and dielectric constant, of the heterogeneous mixtures of textiles and water, can be combined for use into the model. As a next step in the expansion of the model, the model can be configured to account for the drying cycle of the system which will require the model to account for the phase changes that the water will undergo.Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013.
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Prabahar, Jasila. "Localization of Stroke Using Microwave Technology and Inner product Subspace Classifier." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-111585.
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Stroke or “brain attack” occurs when a blood clot carried by the blood vessels from other part of the body blocks the cerebral artery in the brain or when a blood vessel breaks and interrupts the blood flow to parts of the brain. Depending on which part of the brain is being damaged functional abilities controlled by that region of the brain is lost. By interpreting the patient’s symptoms it is possible to make a coarse estimate of the location of the stroke, e.g. if it is on the left or right hemisphere of the brain. The aim of this study was to evaluate if microwave technology can be used to estimate the location of haemorrhagic stroke. In the first part of the thesis, CT images of the patients for whom the microwave measurement are taken is analysed and are used as a reference to know the location of bleeding in the brain. The X, Y and Z coordinates are calculated from the target slice (where the bleeding is more prominent). Based on the bleeding coordinated the datasets are divided into classes. Under supervised learning method the ISC algorithm is trained to classify stroke in the left and right hemispheres; stroke in the anterior and posterior part of the brain and the stroke in the inferior and superior region of the brain. The second part of the thesis is to analyse the classification result in order to identify the patients that were being misclassified. The classification results to classify the location of bleeding were promising with a high sensitivity and specificity that are indicated by the area under the ROC curve (AUC). AUC of 0.86 was obtained for bleedings in the left and right brain and an AUC of 0.94 was obtained for bleeding in the inferior and superior brain. The main constraint was the small size of the dataset and few availability of dataset with bleeding in the front brain that leads to imbalance between classes. After analysis it was found that bleedings that were close to the skull and few small bleedings that are deep inside the brain are being misclassified. Many factors can be responsible for misclassification like the antenna position, head size, amount of hair etc. The overall results indicate that SDD using ISC algorithm has high potential to distinguish bleedings in different locations. It is expected that the results will be more stable with increased patient dataset for training.
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Strydom, M. L. "Design of equal division microwave power dividers." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53353.
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Thesis (MScEng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: Equal division microwave power dividers are investigated in this study. A wideband Wilkinson power divider and a wideband directional coupler with a centre frequency of 10 GHz were built. The design of the directional coupler is scaled, such that it can be used between 18 and 40 GHz. The details of the electromagnetic analyses of these structures are discussed and physical implementation issues are investigated. In a complementary study to the design of planar microwave dividers, the FDTD computational method was implemented and used to analyse the Wilkinson divider and the 18 to 40 GHz directional coupler. Results are compared to those obtained from commercial numerical method packages and in the case of the Wilkinson divider, to measured results. Suggestions are made for improvements in the implementation of the directional coupler and methods for a more efficient FDTD implementation are discussed.
AFRIKAANSE OPSOMMING: Mikrogolf drywings verdelers wat gelyk verdeel, word in hierdie studie ondersoek. ’n Wyeband Wilkinson verdeler en wyeband gerigte koppelaar met ’n senter frekwensie van 10 GHz is gebou. Die onwerp van die gerigte koppelaar is ook geskaleer sodat die ontwerp gebruik kan word tussen 18 en 40 GHz. Die details van die elektromagnetiese analise van hierdie strukture word bespreek en kwessies rondom die implementering van die strukture word ondersoek. In ’n komplementere studie, is die Eindige Verskil Tyd Gebied numeriese metode (Engels: FDTD) geimplimenteer en gebruik om die Wilkinson en die 18 tot 40 GHz gerigte koppelaar te analiseer. Resultate word vergelyk met resultate verkry met numeriesie metodes geimplimenteer in kommersiele pakkette, en in die geval van die Wilkinson verdeler, ook met gemete resultate. Aanbevelings word verder gemaak vir verbeterings in die implementering van die gerigte koppelaar asook metodes om ’n meer effektiewe FDTD kode te implementeer.
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Vega, Sánchez Berta. "New insights in vulcanization chemistry using microwaves as heating source." Doctoral thesis, Universitat Ramon Llull, 2008. http://hdl.handle.net/10803/9292.
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La vulcanització per microones és un procés madur i no hi ha dubte sobre la seva eficiència per produir articles de cautxú d'alta qualitat. Les microones són conegudes no només per la seva capacitat d'accelerar els processos i augmentar la eficiència de la transferència energètica, sinó que també són capaces en certs casos de canviar els camins de reacció. Hi ha evidències, basades en canvis en propietats físiques al comparar productes vulcanitzats amb el mètode convencional i amb microones, que indiquen que alguns canvis poden succeir al treballar amb diferents fonts d'escalfament. No obstant això, hi ha una falta d'informació sobre els efectes que les microones tenen en la química de la vulcanització. Per tant, el principal objectiu d'aquesta tesi es basa en estudiar la vulcanització assistida amb microones des d'una nova perspectiva, centrant-se en els efectes d'aquesta radiació en els ingredients principals de les formulacions de cautxú, en el mecanisme de vulcanització, en la reticulació de la xarxa polimèrica i també en el procés de devulcanització.La primera part de la feina va consistir en desenvolupar i optimitzar tots els mètodes analítics necessàris per explorar totes les etapes del procés de vulcanització i identificar tots els intermedis formats. Estudis de Model Compound Vulcanization (MCV) utilitzant esqualè com a molècula model s'han realitzat per entendre millor la influència d'aquesta radiació en el mecanisme de la reacció, encara que alguns experiments també s'han realitzat amb mostres de cautxú natural. Tècniques com HPLC-MS, MALDI-TOF o GPC s'han utilitzat per caracteritzar les mostres de MCV, mentre que mesures d'inflament, de tensió-elongació, compressió i duresa s'han realitzat per caracteritzar les mostres de cautxú natural.
Dos dels sistemes de vulcanització més comuns han estat estudiats (sulfenamides i tiurams). A més, s'ha donat un especial èmfasi a l'estudi de la influència de les microones en el sistema activador, intentant reduir el contingut de ZnO i cercar, a través de diverses estratègies, substituts més amigables amb el medi ambient. Finalment, tot el coneixement adquirit en aquests estudis s'ha utilitzat per optimitzar el comportament devulcanitzant del disulfur de difenil (DPDS) amb l'ajut de les microones, demostrant que les microones poden ajudar a avançar en la recerca d'una solució al problema del reciclatge dels residus de cautxú.
La vulcanización por microondas es un proceso maduro y no cabe duda sobre su eficiencia para producir artículos de caucho de alta calidad. Las microondas son conocidas no sólo por su capacidad de acelerar los procesos y aumentar la eficiencia de la transferencia energética, sino que también son capaces en ciertos casos de cambiar los caminos de reacción. Hay evidencias, basadas en cambios en propiedades físicas al comparar productos vulcanizados con el método convencional y con microondas, que indican que algunos cambios pueden suceder al trabajar con diferentes fuentes de calentamiento. Sin embargo, hay una falta de información sobre los efectos que las microondas tienen en la química de la vulcanización. Por lo tanto, el principal objetivo de esta tesis se basa en estudiar la vulcanización asistida por microondas desde una nueva perspectiva, centrándose en los efectos de esta radiación en los ingredientes principales de las formulaciones de caucho, en el mecanismo de vulcanización, en la reticulación de la red polimérica y también en el proceso de devulcanización.
La primera parte del trabajo consistió en desarrollar y optimizar todos los métodos analíticos necesarios para explorar todas las etapas del proceso de vulcanización y identificar todos los intermedios formados. Estudios de Model Compound Vulcanization (MCV) utilizando escualeno como molécula modelo se han realizado para entender mejor la influencia de esta radiación en el mecanismo de la reacción, aunque algunos experimentos también se han realizado con muestras de caucho natural. Técnicas como HPLC-MS, MALDI-TOF o GPC se han utilizado para caracterizar las muestras de MCV, mientras que medidas de inflamiento, de tensión-elongación, compresión y dureza se han realizado para caracterizar las muestres de caucho natural.
Dos de los sistemas de vulcanización más comunes han sido estudiados (sulfenamidas y tiuramos). Además, se ha dado un especial énfasis al estudio de la influencia de las microondas en el sistema activador, intentando reducir el contenido en ZnO y buscar, a través de diversas estrategias, substitutos más amigables con el medio ambiente. Finalmente, todo el conocimiento adquirido en estos estudios se ha utilizado para optimizar el comportamiento devulcanitzante del disulfuro de difenilo (DPDS) con ayuda de las microondas, demostrando que las microondas pueden ayudar a avanzar en la búsqueda de una solución al problema del reciclaje de los residuos de caucho.
Microwaves vulcanization is a mature process and there is no doubt about its efficiency on producing high quality goods. Microwaves are found not only to speed up the processing and increase the energy transfer efficiency, but also to be in some cases able to change reaction pathways. There are some evidences, based on changes in physical properties when comparing conventional and microwaves vulcanization, that suggest that some changes occur when working with different heating sources. However, there is a lack of information of the effects of MW in vulcanization chemistry. Therefore, the principal aim of this thesis consists of studying microwave-assisted vulcanization from a new perspective, focusing on the effects of this radiation in the main ingredients of a rubber compound, in the vulcanization mechanism, in the final crosslinked network and also in the devulcanization process.
The first part of the work consisted in developing and optimizing all the analytical methods necessary to explore all the steps of vulcanization process and identifying all the intermediates formed. Model Compound Vulcanization (MCV) studies, using squalene as a model molecule, have been used to understand better the influence of this radiation in the reaction mechanism, even though some tests have been also performed in natural rubber samples. Techniques as HPLC-MS, MALDI-TOF or GPC have been used to characterize the MCV samples, whereas swelling measurements, stress-strain measurements, compression set or hardness have been used to characterized natural rubber samples.
Two of the most common vulcanizing systems have been studied (using sulfenamide and/or thiuram accelerator types). In addition, a special emphasis has been given to the study of the microwaves influence on the activator system, trying to reduce ZnO contents and finding more environmental friendly substitutes through different strategies. Finally, all the knowledge acquired in all these studies has been used to optimize the devulcanizing behavior of diphenyl disulfide (DPDS) with the help of microwaves, proving that microwaves can help to advance in the search of a solution to the problem of waste rubber recycling.
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Kalra, Aashish. "Dewatering of fine coal slurries by selective heating with microwaves." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4536.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Crowder, I. D. "The use of microwaves to control pests of stored products." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371914.
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Suckling, James Rowland. "Transmission of microwaves through subwavelength slits and holes in metal." Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426088.
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Haslett, Christoper. "Modelling and measurement of the diffraction of microwaves by buildings." Thesis, University of South Wales, 1993. https://pure.southwales.ac.uk/en/studentthesis/modelling-and-measurement-of-the-diffraction-of-microwaves-by-buildings(7ca4ddff-7a5f-4e29-b49d-3c66d859a1e2).html.
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Much of the recent growth in microwave communication systems has occurred within urban areas. Private satellite and point to point microwave services have meant that microwave antennas are a common site on the roofs of offices. With the increase in system density comes the increase in the probability of mutual interference between systems sharing the same frequency band. However, the urban location of these systems means that there is also a greater possibility of a building obstructing the interference path, thus providing protection. Because the introduction of microwave systems into an urban environment on such a scale is a relatively recent event, little information was available regarding the effect of a building on a radio path at microwave frequency. This thesis provides a procedure by which the diffracted field in the shadow of a building may be determined. Diffraction models are developed based on Fresnel Integral methods and tested against results obtained from a measurement campaign conducted at a frequency of 11.2 GHz using real buildings as the diffracting obstacles. The diffraction model developed is extended from originally considering a two-dimensional great circle path to one which considers multiple path diffraction, typically via the roof and around the sides of the building. It has therefore been possible to formulate procedures suitable for incorporation into CCIR recommendations whereby the presence of a building may be considered when determining coordination distance and evaluating practical interference threats on specific paths. Finally methods by which the diffraction mechanism investigated may be incorporated into generalised signal strength prediction procedures that would consider other mechanisms, such as building scatter, are put forward.
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Feldman, Andrew F. "Multiple scattering of microwaves from soil surface and vegetation canopies." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119332.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 67-71).
A multiple scattering radiative transfer model is developed for use in global retrieval algorithms of microwave geophysical parameters. This attempts to both improve soil moisture and vegetation attenuation and scattering parameter retrievals under moderate to dense canopy covers and capture the full microwave vegetation signature. The model is developed using a ray tracing method of first-order interactions with canopy constituents larger than 21 cm (e.g. woody biomass). It introduces only one new variable, [omega]₁ representing scattering from these constituents, making it almost as computationally efficient to implement as the commonly used tau-omega (zeroth-order) model. With concerns for vegetation cover changes with climate change, there is motivation to monitor vegetation cover properties and respective available surface water availability. The retrieval of microwave vegetation attenuation and scattering parameters provides a unique opportunity to monitor vegetation parameters in addition to commonly used optical remote sensing of vegetation techniques. The model is applied within the recently developed and hereby enhanced Multi-Temporal Dual Channel Algorithm (MT-DCA) framework. The algorithm is implemented over Africa using SMAP 36 km brightness temperature radiometric measurements using both zeroth and first-order radiative transfer models. The first-order radiative transfer model is determined to be more sensitive to surface emission resulting in an improved surface emission signature from retrievals. The retrieved [omega]₁ are also greatest in forests noting the presence of woody biomass and resulting in first-order emission contributing to 5% of the total emission. Consequently, changes from zeroth to first-order retrievals occur primarily in vegetated regions where [omega]₁ is non-zero. Non-zero [omega]₁ additionally results in improved fit of parameters to SMAP measurements. Without a comprehensive forest in-situ measurement campaign, it is inconclusive whether the introduced first-order radiative transfer model improves retrievals over SMAP and SMOS baseline retrievals. Additionally, further work in developing global retrieval algorithms aimed at retrieving both surface and vegetation microwave parameters amongst moderate to dense vegetation is encouraged.
by Andrew F. Feldman.
S.M.
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Ding, Ming Sheng. "Modelling and measurement of the scatter of microwaves by buildings." Thesis, University of South Wales, 1994. https://pure.southwales.ac.uk/en/studentthesis/modelling-and-measurement-of-the-scatter-of-microwaves-by-buildings(ab8b0911-5e4f-48ed-882c-d646b5df266f).html.
Full textAbstract:
The growing usage and demand for microwave communications has led to the increase in system density, particularly in urban areas, and consequently to the increase in the probability of mutual interference between systems sharing the same frequency band. Satellite and point to point microwave communication systems might have to rely on site shielding to reduce the level of this co-channel interference. In urban areas, there is a great possibility of a building obstructing the interference path, thus providing protection. However, there could be more than one interference path. Scattered interference from other buildings in the vicinity of the site is one which can be found to be almost as harmful as the direct interference. Although site shielding has long been identified as an interference reduction technique, most studies have been devoted to the protection obtained from the obstruction of interference paths, namely diffraction. There is little information available regarding the effects of building scatter in site shielding. The work reported in this thesis was set to carry out theoretical and experimental investigations and characterisation of building scatter. The studies are aimed at the effects of building scatter on site shielding at microwave frequencies. Building scatter prediction models are developed based on Fresnel-Kirchhoff diffraction theory and verified against results obtained from measurement campaigns conducted at a frequency of 11.2 GHz using firstly a perfectly conducting reflector and later a number of buildings in urban environments as the scattering obstacles. Scattering prediction models are developed as extending to that originally applicable to the far field for use in the near and very near field regions of the scattering surface. The very near field model is found to be particularly useful in site shielding applications in urban environments. Furthermore, it has been possible to establish the scattering characteristics in terms of angular and distance dependence of the scattering coefficient using the expansions of the Fresnel integral with appropriate approximations. The effects of building features and surface variations, e.g. protruding and recessed features, windows and surface deviations, are analysed and characterised. These effects are particularly significant in the interpretation of measurement results obtained from buildings in typical urban environments. The thesis provides a prediction procedure which radio system planners and design engineers can use for determining the effects of building scatter on the site shielding factor for specified radio path geometries. The procedure is expected, through UK study group 3, to add considerably to a revised ITU-R (CCIR) procedure and recommendations for building scatter effects in radiowave propagation. The work has also contributed regularly to the technical output of European COST project 235.
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Jones, Robin Ellis. "Use of microwaves for the detection of corrosion under insulation." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10527.
Full textAbstract:
Corrosion Under Insulation (CUI) is a widespread problem throughout the oil and gas industry, and is a major cause of pipeline failure. CUI occurs on pipelines fitted with thermal insulation; the insulation itself is protected from the environment by a layer of metallic cladding and sealed to prevent water ingress. This cladding can deteriorate from age or become damaged, allowing the ingress of water into the insulation, which allows corrosion of the external pipe surface to initiate. This corrosion can proceed at an accelerated rate due to the elevated process temperature of the pipe, compromising the integrity of the pipeline. The detection of this type of corrosion is an ongoing problem for the oil and gas industry, as the insulation system conceals the condition of the pipe. Therefore, there is a requirement for a long-range, screening inspection technique which is sensitive to the first ingress of water into the insulation, in order to provide an early warning of areas of a pipeline at risk from CUI. This thesis describes the development of a new inspection technique which employs guided microwaves as the interrogating signal. Such guided microwaves provide a means of screening the length of a pipeline for wet insulation, by using the structure of a clad and insulated pipeline as a coaxial waveguide to support the propagation of electromagnetic waves. Areas of wet insulation will create impedance discontinuities in the waveguide, causing reflections of the incident microwave signal, allowing the water patches to be detected and located. The performance of such a guided wave inspection system is intrinsically linked to the signal-to-coherent-noise ratio (SCNR) that can be achieved. Therefore, the value of the SCNR that the technique is capable of achieving is of central importance to this thesis. The excitation system is optimised to maximise the SCNR, whilst the effect of typical pipeline features such as bends, pipe supports and the various types of insulation which can be used, are studied to quantify the effect on the SCNR. A wide variety of methods are employed throughout the development of the guided microwave technique described in this thesis. Theoretical methods are employed in the initial stages to enable the development of a model to describe electromagnetic wave propagation in the large coaxial waveguides formed by pipelines. Numerical simulation techniques are employed when there are too many parameters to study for experimentation to be a viable option, and to study complex problems for which no analytical solution exists. Experiments are conducted in the laboratory using a model setup which employs metallic ducting to represent an insulated pipeline. These experiments are performed to demonstrate the practical feasibility of the technique, and to study pipeline features in a controlled environment. Finally, experiments are performed in the field on a section of real industrial pipeline, in order to validate the accuracy of the model experimental setup in representing conditions which exist on real pipelines. The main findings of the thesis are that it is possible to excite a guided microwave signal in a large coaxial waveguide with a high SCNR. Experiments revealed that the technique is highly sensitive to the presence of water in the waveguide. Measurements of the effect of different types of insulation demonstrated that rockwool causes a very low attenuation of the microwave signal, while polyurethane foam insulation has a slightly higher attenuation coefficient. An investigation into the effect of bends determined that, whilst significant mode conversion occurs at a bend, the transmission coefficient of the TEM mode is high for typical bend angles and bend radii in small diameter pipes. The behaviour of the signal at a typical pipe support was also examined; the reflection from the support was minimal, whilst the transmission beyond the support remained relatively high. Whilst there is still further work to be done before this technique can be applied in the field, the major aspects of practical implementation that could affect the technique have been investigated here, and the results consistently indicate the feasibility of the technique for long-range screening of insulated pipelines for water.
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Vliet, F. E. "Microwaves. When waves matter over kleine zaken met grote gevolgen /." Enschede : University of Twente [Host], 2009. http://doc.utwente.nl/60625.
Full text
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Spadoni, Paolo <1980>. "Nonlinear/electromagnetic co-simulation of microwaves and millimeter-waves links." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/935/1/Tesi_Spadoni_Paolo.pdf.
Full textAbstract:
The Ph.D. thesis describes the simulations of different microwave links from the
transmitter to the receiver intermediate-frequency ports, by means of a rigorous circuit-level
nonlinear analysis approach coupled with the electromagnetic characterization of the transmitter
and receiver front ends. This includes a full electromagnetic computation of the radiated far field
which is used to establish the connection between transmitter and receiver. Digitally modulated
radio-frequency drive is treated by a modulation-oriented harmonic-balance method based on
Krylov-subspace model-order reduction to allow the handling of large-size front ends.
Different examples of links have been presented: an End-to-End link simulated by making
use of an artificial neural network model; the latter allows a fast computation of the link itself when
driven by long sequences of the order of millions of samples. In this way a meaningful evaluation of
such link performance aspects as the bit error rate becomes possible at the circuit level.
Subsequently, a work focused on the co-simulation an entire link including a realistic simulation of
the radio channel has been presented. The channel has been characterized by means of a
deterministic approach, such as Ray Tracing technique. Then, a 2x2 multiple-input multiple-output
antenna link has been simulated; in this work near-field and far-field coupling between radiating
elements, as well as the environment factors, has been rigorously taken into account. Finally,
within the scope to simulate an entire ultra-wideband link, the transmitting side of an ultrawideband
link has been designed, and an interesting Front-End co-design technique application has
been setup.
50
Spadoni, Paolo <1980>. "Nonlinear/electromagnetic co-simulation of microwaves and millimeter-waves links." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/935/.
Full textAbstract:
The Ph.D. thesis describes the simulations of different microwave links from the
transmitter to the receiver intermediate-frequency ports, by means of a rigorous circuit-level
nonlinear analysis approach coupled with the electromagnetic characterization of the transmitter
and receiver front ends. This includes a full electromagnetic computation of the radiated far field
which is used to establish the connection between transmitter and receiver. Digitally modulated
radio-frequency drive is treated by a modulation-oriented harmonic-balance method based on
Krylov-subspace model-order reduction to allow the handling of large-size front ends.
Different examples of links have been presented: an End-to-End link simulated by making
use of an artificial neural network model; the latter allows a fast computation of the link itself when
driven by long sequences of the order of millions of samples. In this way a meaningful evaluation of
such link performance aspects as the bit error rate becomes possible at the circuit level.
Subsequently, a work focused on the co-simulation an entire link including a realistic simulation of
the radio channel has been presented. The channel has been characterized by means of a
deterministic approach, such as Ray Tracing technique. Then, a 2x2 multiple-input multiple-output
antenna link has been simulated; in this work near-field and far-field coupling between radiating
elements, as well as the environment factors, has been rigorously taken into account. Finally,
within the scope to simulate an entire ultra-wideband link, the transmitting side of an ultrawideband
link has been designed, and an interesting Front-End co-design technique application has
been setup.