Dissertations / Theses on the topic 'Modelling of microwave systems'
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Ehlers, Richard Alfred. "Modelling of packaging systems in microwave fields." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621389.
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REALINI, SABRINA. "ANALYSIS OF THE STRIP OPTICAL SYSTEM FOR CMB POLARIZATION MEASUREMENTS." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/783084.
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Nowadays, the detection of B-mode polarization anisotropies on large angular scales in the Cosmic Microwave Background polarization pattern is one of the major challenges in observational cosmology. In fact, it would give us an evidence in favor of the inflationary paradigm, shedding light on the physics of the very early Universe. Unfortunately, the amplitude of the signal is extremely low, at fractions of µK, and its detection requires high sensitivity instruments with thousands of detectors, a rigorous control of systematic effects, and a precise knowledge of the foreground polarized emission of our Galaxy.
The Large Scale Polarization Explorer is one of the upcoming experiments devoted to the observation of the CMB polarization on large angular scales. It is based on two independent instruments: the STRIP ground-based telescope and the SWIPE balloon-borne mission.
This thesis has been carried out in the context of the development of the STRIP instrument, a coherent polarimeter array that will observe the microwave sky from the Teide Observatory in Tenerife in two frequency bands centred at 43 and 95 GHz through a dual-reflector crossed-Dragone telescope of 1.5 m aperture.
We present the implementation of the realistic electromagnetic model of the STRIP telescope, which includes all its optical elements and the surrounding structures. Since accurate predictions and measurements of the beam shape are essential both during the instrument design phase and for an in-depth knowledge of the whole-instrument response, we performed detailed optical simulations of the beam radiation properties.
The results have been essential to assess the impact of the optical response on CMB polarization measurements when observing the sky with the nominal scanning strategy. This activity was mandatory because the optics is one of the major limiting factors for high precision measurements.
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Salah, Adham M. S. "Investigation of Integrated Decoupling Methods for MIMO Antenna Systems. Design, Modelling and Implementation of MIMO Antenna Systems for Different Spectrum Applications with High Port-to-Port Isolation Using Different Decoupling Techniques." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/18427.
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Multiple-Input-Multiple-Output (MIMO) antenna technology refers to an antenna with
multiple radiators at both transmitter and receiver ends. It is designed to increase the data rate in
wireless communication systems by achieving multiple channels occupying the same bandwidth
in a multipath environment. The main drawback associated with this technology is the coupling
between the radiating elements. A MIMO antenna system merely acts as an antenna array if the
coupling between the radiating elements is high. For this reason, strong decoupling between the
radiating elements should be achieved, in order to utilize the benefits of MIMO technology.
The main objectives of this thesis are to investigate and implement several printed MIMO
antenna geometries with integrated decoupling approaches for WLAN, WiMAX, and 5G
applications. The characteristics of MIMO antenna performance have been reported in terms of
scattering parameters, envelope correlation coefficient (ECC), total active reflection coefficient
(TARC), channel capacity loss (CCL), diversity gain (DG), antenna efficiency, antenna peak gain
and antenna radiation patterns.
Three new 2×2 MIMO array antennas are proposed, covering dual and multiple spectrum
bandwidths for WLAN (2.4/5.2/5.8 GHz) and WiMAX (3.5 GHz) applications. These designs
employ a combination of DGS and neutralization line methods to reduce the coupling caused by
the surface current in the ground plane and between the radiating antenna elements. The minimum
achieved isolation between the MIMO antennas is found to be better than 15 dB and in some
bands exceeds 30 dB. The matching impedance is improved and the correlation coefficient values
achieved for all three antennas are very low. In addition, the diversity gains over all spectrum
bands are very close to the ideal value (DG = 10 dB).
The forth proposed MIMO antenna is a compact dual-band MIMO antenna operating at
WLAN bands (2.4/5.2/5.8 GHz). The antenna structure consists of two concentric double square
rings radiating elements printed symmetrically. A new method is applied which combines the
defected ground structure (DGS) decoupling method with five parasitic elements to reduce the
coupling between the radiating antennas in the two required bands.
A metamaterial-based isolation enhancement structure is investigated in the fifth proposed
MIMO antenna design. This MIMO antenna consists of two dual-band arc-shaped radiating
elements working in WLAN and Sub-6 GHz 5th generation (5G) bands. The antenna placement
and orientation decoupling method is applied to improve the isolation in the second band while
four split-ring resonators (SRRs) are added between the radiating elements to enhance the
isolation in the first band.
All the designs presented in this thesis have been fabricated and measured, with the simulated
and measured results agreeing well in most cases.Higher Committee for Education Development in Iraq (HCED)
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Palierakis, Y. "Non-intrusive flow measurement of pneumatically conveyed solids; physical modelling and application of spatial windowing to improve microwave and electrostatic sensors : Conveyed solids velocity measurement systems based on transit time correlation and th." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371496.
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Three sensor systems measuring particle velocity in gas-solids flows have been studied. These are the microwave Doppler flow sensor, the electrostatic sensor, and the microwave sensor for correlation measurement, all utilizing different principles of operation. The Doppler sensor is based on the Doppler frequency shift observed when microwaves are backscattered by moving targets. An analysis of the process of Doppler signal generation and a computer model based on this analysis have been presented. A novel feature of this work is the implementation of partial screening of the flow field which improves the shape of the Doppler spectrum and results in a mean Doppler frequency proportional to the flow velocity and independent of the flow profile. The electrostatic sensor is based on the principle of monitoring the charge induced on metallic surfaces by charged particles moving in their neighbourhood. A theoretical analysis of the spatial performance of the sensor along with a computer model and experimental verification are presented. Principally, ring type of sensors have been examined and the streched band electrostatic sensor is introduced (SBES). The advantage gained with the introduction of the stretched band electrostatic sensor is a uniform sensitivity across the plane of the sensor. The microwave correlation sensor follows the principles of previous ultrasonic and laser correlation flovrneters. That is, "a transmitted beam penetrates the flow field, suffers modulation, and is detected by receivers placed on the other side of the flow field. An analysis of the principles has been presented and a simplified computer model has been used for system design studies. The study presented here shows that a microwave correlation sensor is viable device for measuring solids velocity. Wherever possible direct comparisons of the properties and the performance of the three sensors are made in order to draw conclusions as to which sensor is best for a specific industrial application. Engineering, environmental and safety problems which might be encountered in the practical implementation of the sensors are discussed. In addition, areas of uncertainty where further work is required are summarized.
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Aboualmal, Abdulhadi M. A. "Analysis and modelling of the impact of anomalous propagation on terrestrial microwave links in a subtropical region, based on long-term measurements : statistical analysis of long-term meteorological and signal strength measurements in a subtropical region and investigation of the impact of anomalous refractivity profiles on radio propagation in terrestrial microwave wireless systems." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14804.
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Prevailing propagation phenomena in certain areas play a vital role in deciding terrestrial wireless systems performance. Vertical refractivity profile below 1 km is a critical parameter for designing reliable systems; noting that there is a shortage of upper-air data worldwide. Anomalous phenomena may cause severe signal fading and interference beyond the horizon. The objectives of this thesis are to investigate dominant refractive conditions in the subtropical Arabian Gulf region, develop new approaches and empirical models for evaluating vertical refractivity profiles and relevant propagation parameters in the low troposphere, and to examine the impact of frequently experienced anomalous phenomena on terrestrial microwave links. Twenty-three years of meteorological measurements, from 1990 to 2013, are utilized using spatially separated surface stations and a single radiosonde in the United Arab Emirates (UAE). Profiles of sea level, surface and upper refractivity components are statistically analysed. Three major atmospheric layers; namely 65 m, 100 m and 1 km above the ground are studied to analyse relevant propagation parameters such as sub-refraction, super-refraction, anomalous propagation probability parameter β0 and point refractivity gradient not exceeded for 1% of time. The effective earth radius factor k is investigated using a new weighted averaged approach. In addition, the seasonal structure of atmospheric ducting is dimensioned within 350 m layer above ground. Finally, microwave measurement campaign is conducted using multiple radio links operating in UAE using various frequency bands. The link budget simulations are compared with the signal strength measurements. Fading scenarios are studied against the observed anomalous conditions and several recommendations are concluded.
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Lundgren, Nils. "Modelling microwave measurements in wood /." Luleå, 2005. http://epubl.luth.se/1402-1757/2005/61.
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Vegh, Viktor. "Numerical modelling of industrial microwave heating." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/37144/7/37144_Digitised%20Thesis.pdf.
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The numerical modelling of electromagnetic waves has been the focus of many research areas in the past. Some specific applications of electromagnetic wave scattering are in the fields of Microwave Heating and Radar Communication Systems. The equations that govern the fundamental behaviour of electromagnetic wave propagation in waveguides and cavities are the Maxwell's equations. In the literature, a number of methods have been employed to solve these equations. Of these methods, the classical Finite-Difference Time-Domain scheme, which uses a staggered time and space discretisation, is the most well known and widely used. However, it is complicated to implement this method on an irregular computational domain using an unstructured mesh.
In this work, a coupled method is introduced for the solution of Maxwell's equations. It is proposed that the free-space component of the solution is computed in the time domain, whilst the load is resolved using the frequency dependent electric field Helmholtz equation. This methodology results in a timefrequency domain hybrid scheme. For the Helmholtz equation, boundary conditions are generated from the time dependent free-space solutions. The boundary information is mapped into the frequency domain using the Discrete Fourier Transform. The solution for the electric field components is obtained by solving a sparse-complex system of linear equations. The hybrid method has been tested for both waveguide and cavity configurations. Numerical tests performed on waveguides and cavities for inhomogeneous lossy materials highlight the accuracy and computational efficiency of the newly proposed hybrid computational electromagnetic strategy.
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Dibben, David. "Numerical and experimental modelling of microwave applicators." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/237037.
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This thesis presents a time domain finite element method for the solution of microwave heating problems. This is the first time that this particular technique has been applied to microwave heating. It is found that the standard frequency domain finite element method is unsuitable for analysing multimode applicators containing food-like materials due to a severe ill-conditioning of the matrix equations. The field distribution in multimode applicators loaded with low loss materials is found to be very sensitive to small frequency changes. Several solutions at different frequencies are therefore required to characterise the behaviour of the loaded applicator. The time domain finite element method is capable of producing multiple solutions at different frequencies when used with Gaussian pulse excitation; it is therefore ideally suited to the analysis of multimode applicators. A brief survey of the methods available for the solution of the linear equations is provided. The performance of these techniques with both the frequency domain and time domain finite element methods is then studied. Single mode applicators are also analysed and it is found that the frequency domain method is superior in these cases. Comparisons are given between the calculated results and experimental data for both single mode and multimode systems. The importance of experimental verification being stressed. The choice of element type is an important consideration for the finite element method. Three basic types of element are considered; nodal, Whitney edge elements and linear edge elements. Comparisons of the errors with these elements show that Whitney elements produce a consistently lower error when post-processing is used to smooth the solution. The coupled thermal-electromagnetic problem is investigated with many difficulties being identified for the application to multimode cavity problems.
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Schoeman, Marlize. "Interpolation-based modelling of microwave ring resonators." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1192.
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Sum, Kam Chung. "Combined microwave optoelectronic modelling for semiconductor lasers." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337319.
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Turati, Paolo. "FDTD modelling of nanostructures at microwave frequency." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/9062.
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The thesis which is hereby presented describes a study of the numerical modelling of the coupled interaction of nanostructures with electromagnetic fields in the range of microwaves. This is a very ambitious task and requires a thorough and rigorous implementation of new algorithms designed to this purpose. The first issue to be encountered is the characterisation and the physical understanding of the behaviour of a nanostructure. The term itself, nanostructure, defines any device which has a nanometric size in at least one dimension, regardless of its material and geometry, hence it is a very wide definition. Carbon Nanotubes (CNT), quantum dots and quantum wells fall into this category, for example, and in electronics these structures are generally composed of semiconductor materials, like Silicon or Gallium Arsenide. The first step to take, in order to model such objects from an electronics point of view, is to solve the Schrodinger equation. The Schrodinger equation is a very general formula, widely used in quantum physics, which, when provided with a certain electrical potential in a material, determines the behaviour of the electrons in this material. Needless to say, the electrical potential is the DNA of a material or, in other words, it is the physical property which affects the propagation of electrons and therefore makes a material conducting or non-conducting. Nanostructures are often composed of several materials, hence the potential is not constant and, with opportune geometries, it is possible, in principle, to guide the electron currents through the device, as, for example, a channel in a MOSFET. This principle holds for very small structures where the electron transport can be considered ballistic, i.e. when the structures are smaller than the free mean path of the particle. The behaviour of the electrons is affected both by external factors, such as temperature or applied electric and magnetic fields, and internal factors, such as the electron mobility or the doping concentration, which are dependent on the used materials. This parameters play a very important role whilst modelling the behaviour of particles such as electrons and in this work the main focus is the study of the impact of external electromagnetic fields. The electromagnetic fields (EM fields) are composed of an electric field component and of a magnetic field component, which can be analysed separately in order to better understand the response of nanostructures to their application. A rigorous analysis is presented by showing numerical results, obtained with the modelling of the Schrodinger equation, compared with the expected theoretical results, exploiting simple structures, where it is possible to calculate the solutions analytically. The second part of thesis focuses on the impact of the EM fields on the nanostructure, hence the combined effect of both electric and magnetic fields affecting the electrons' propagation, and the mutual coupling of the fields with the quantum effects. Indeed the study of nanodevices for microwave applications requires to consider the contribution of a parameter called quantum current density, which accounts for the quantum effects generated by the structure. This is normally ignored in conventional devices because the quantum contributions are negligible but, by using opportune materials and opportune geometries, these currents become relevant and they may have an impact on the propagation of the EM fields. For this reason a consistent part of the thesis is dedicated to investigate the mutual coupling between EM fields and quantum effects, by implementing the Maxwell-Schrodinger coupled model. A chapter is dedicated to the novel approaches taken in order to tackle the issues and the limits of the numerical implementation; in particular two solutions are presented, nonuniform domains and the parallelisation of the algorithm. These approaches are vital whilst modelling numerically such physical problems since the required computational capacity increases with the accuracy requirements. Solving the presented algorithms conventionally would limit the potential of the method and thus a thorough study has been made in order to improve the efficiency of the simulations. In the last chapter, three different scenarios are presented, each one of them showing different features of the coupled model. The results are illustrated and discussed, including the limits due to the chosen approximations. References to the analytical solutions are provided in order to validate the obtained numerical results.
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Brooks, Clive Raymond. "GaN microwave power FET nonlinear modelling techniques." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4306.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The main focus of this thesis is to document the formulation, extraction and validation of nonlinear models for the on-wafer gallium nitride (GaN) high-electron mobility (HEMT) devices manufactured at the Interuniversity Microelectronics Centre (IMEC) in Leuven, Belgium. GaN semiconductor technology is fast emerging and it is expected that these devices will play an important role in RF and microwave power amplifier applications. One of the main advantages of the new GaN semiconductor technology is that it combines a very wide band-gap with high electron mobility, which amounts to higher levels of gain at very high frequencies. HEMT devices based on GaN, is a fairly new technology and not many nonlinear models have been proposed in literature. This thesis details the design of hardware and software used in the development of the nonlinear models. An intermodulation distortion (IMD) measurement setup was developed to measure the second and higher-order derivative of the nonlinear drain current. The derivatives are extracted directly from measurements and are required to improve the nonlinear model IMD predictions. Nonlinear model extraction software was developed to automate the modelling process, which was fundamental in the nonlinear model investigation. The models are implemented in Agilent’s Advanced Design System (ADS) and it is shown that the models are capable of accurately predicting the measured S-parameters, large-signal singletone and two-tone behaviour of the GaN devices.
AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie tesis is om die formulering, ontrekking en validasie van nie-lineêre modelle vir onverpakte gallium nitraat (GaN) hoë-elektronmobilisering transistors (HEMTs) te dokumenteer. Die transistors is vervaaardig by die Interuniversity Microelectronics Centre (IMEC) in Leuven, België. GaN-halfgeleier tegnologie is besig om vinnig veld te wen en daar word voorspel dat hierdie transistors ʼn belangrike rol gaan speel in RF en mikrogolf kragversterker toepassings. Een van die hoof voordele van die nuwe GaN-halfgeleier tegnologie is dat dit 'n baie wyd band-gaping het met hoë-elektronmobilisering, wat lei tot hoë aanwins by mikrogolf frekwensies. GaN HEMTs is 'n redelik nuwe tegnologie en nie baie nie-lineêre modelle is al voorgestel in literatuur nie. Hierdie tesis ondersoek die ontwerp van die hardeware en sagteware soos gebruik in die ontwikkeling van nie-lineêre modelle. 'n Intermodulasie distorsie-opstelling (IMD-opstelling) is ontwikkel vir die meting van die tweede en hoër orde afgeleides van die nie-lineêre stroom. Die afgeleides is direk uit die metings onttrek en moet die nie-lineêre IMD-voorspellings te verbeter. Nie-lineêre onttrekking sagteware is ontwikkel om die modellerings proses te outomatiseer. Die modelle word geïmplementeer in Agilent se Advanced Design System (ADS) en bewys dat die modelle in staat is om akkurate afgemete S-parameters, grootsein enkeltoon en tweetoon gedrag van die GaN-transistors te kan voorspel.
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Alsadi, Majid Hamid Nassar. "Modelling of electromagnetic material properties at microwave frequencies." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12531/.
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In recent years, electromagnetic interference (EMI) has raised serious issues in terms of the unintentional radiation that disrupts the near proximity equipment from working properly. One solution to reduce the effects of EMI is the use of electromagnetic shielding. Carbon fibre composite (CFC) material is a promising customised product that has entered numerous industrial areas due to its attractive properties like high strength, low weight, and the resistance to chemical substances and corrosion. CFC has started to be used as electromagnetic shields, for example modern computer cases. However, not much is known about its electromagnetic behaviour. This research derives various models for CFC materials for the purpose of achieving better understanding to their interaction with electromagnetic waves at microwave frequencies. Throughout this research, the electrical properties of different materials have been investigated in terms of their shielding effectiveness (SE). The modelling was performed using the transmission-line modelling (TLM) method. The digital filter (DF) technique was used for small structures that are embedded in the system under modelling. In this way, the space mesh can be turned into coarser mesh. While maintaining the same accuracy, this technique has substantially saved on computational resources and has increased the speed of the modelling process. This in turn, has made it more feasible to model large scale practical systems. The formulae of DF cascading were derived to allow modelling systems of multiple embedded structures. Simulated models were validated by comparing them with the corresponding conventional fine mesh results. One-dimensional models were validated with the available analytic solution. Experimental measurements were conducted on panels made of this anisotropic material, which has manifested frequency-dependent characteristics that satisfy Drude model. These measurements have validated the corresponding numerical electromagnetic models. The final product of this study is gaining better knowledge about the electromagnetic behaviour of different materials. This knowledge can help in predicting the shielding performance when these materials are used within large-scale systems.
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Flockhart, Craig. "Simulation of microwave heating using transmission line modelling." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319922.
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Louw, Willem J. "Microwave heating of multiphase materials : modelling and measurement." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/21217.
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Thesis (MScIng)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Both coaxial probe and waveguide (WG) measurement systems for electric and magnetic material property extraction were investigated. These measurement techniques were used to determine electrical properties of an inhomogeneous rock sample in its solid and crushed states. A lumped element model of the probe was used and permittivity was determined by the inversion algorithm developed by Stuchly and Stuchly. To support this technique it was compared to a full wave inversion algorithm and referenced to properties of the same samples but determined by a resonant cavity technique. The Nicholson, Ross and Weir inversion algorithm was used to determine material properties from WG measurements. As a reference, the same techniques were applied to a well defined material. It was found that neither of the measurement techniques could measure low loss factors or conductive materials and literature values were used in these cases. Various simulation models of the multiphase ore in both its solid and crushed states are presented. These models were utilised in finite-difference time-domain (FDTD) simulations of different microwave (MW) cavities. Simulation and experimental S-parameter comparisons are presented. The level of accuracy achieved varies as a function of the geometrical representation and material properties. After an S-parameter comparison with simulation results it was concluded that the electrical properties of both the solid and crushed rocks have been well determined for MW cavity design. Predicted and measured field distributions in cavities were also compared and it is shown that accurate models of multiphase materials become especially important in the determination of field distributions in and around different rock phases. Recommendations for the suggested material property determination and verification processes are presented. A specific application of this work is in the field of microwave assisted comminution.
AFRIKAANSE OPSOMMING: ’n Koaksiale probe en golfgeleier (WG) stelsels vir die bepaling van materiaal eienskappe (elektries en magneties) word gebruik met die doel om ’n nie-homogene rotsmonster te karakteriseer. Die ekstraksie algoritme van Stuchly en Stuchly word gebruik om die materiaal eienskappe te bepaal vanaf die gemete S11-parameter. Hierdie ekstraksie metode word vergelyk met ’n vol golf ekstraksie van permitiwiteit vanaf dieselfde gemete data. Beide die ekstraksie metodes word dan vergelyk met resonante holte meetings van dieselfde materiale. Die Nicholson, Ross en Weir ekstraksie algoritme word toegepas op meetings wat gedoen is deur die golfgeleier stelsel. As ’n verwysing word dieselfde tegnieke toegepas op ’n bekende materiaal en daar is gevind dit stem goed ooreen behalwe dat nie een van die twee meet tegnieke lae verlies faktore kan meet nie. Verder kan nie een van die twee sisteme geleidende materiale meet nie. Vir sulke gevalle is waardes nageslaan. Verskeie simulasiemodelle van die rots word voorgestel vir beide soliede en vergruisde monsters. Hierdie modelle word gebruik in FDTD simulasies van verskeie mikrogolftoevoegers met die oog om ’n vergelyking te tref tussen gesimuleerde en gemete S-parameters. Verskillende vlakke van akkuraatheid is bereik en is ’n funksie van die geometrie en die materiaaleienskappe van die model. Nadat gemete en gesimuleerde S-parameters vergelyk is, is gevind dat die materiaal eienskappe van beide die soliede en vergruisde rots monsters goed bepaal is vir mikrogo lf toevoeger ontwerp. Voorspelde en gemete veldverspreidings word ook vergelyk en dit is veral hierso van belang om ’n realistiese model van die nie-homogene monster te gebruik. Sekere voorstelle word gemaak om die verskillende aspekte van die meet van ma teriaaleienskappe en simulasiemodelle te kan verfyn. ’n Spesifieke toepassing van hierdie werk is in mikrogolf ondersteunde skeiding van minerale en erts.
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Bokhoree, Chandradeo. "Mathematical modelling of microwave-enhanced chemical vapour infiltration." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/35280.
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With their excellent high temperature mechanical, chemical and thermal properties, fibre reinforced ceramic matrix composites have emerged as an important class of materials having a wide range of applications in various technological fields. Microwave Enhanced Chemical Vapour Infiltration (MECVI) has been recognized as a new process route because of its ability to conserve the reliability and durability of the precursor materials. The primary advantage of using microwaves is that they cause an inverse temperature profile to be formed that prevents entrapment of accessible porosity and greatly accelerates the process. However, to develop the MECVI process further, a complete understanding of the effects of the process parameters on the infiltration mechanism and processing time is necessary. Modelling efforts can offer an insight into the critical factors in this process and suggest ways to optimize processing. A 2-D mathematical model investigating the densification of SiCf/SiC composites by microwave enhanced Chemical Vapour Infiltration (CVI) under forced-flow of the gaseous reactants is presented.
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DI, GIACOMO Valeria. "ELECTRON DEVICE NONLINEAR MODELLING FOR MICROWAVE CIRCUIT DESIGN." Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2389216.
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The electron device modelling is a research topic of great relevance, since the performances
required to devices are continuously increasing in terms of frequency, power and linearity: new
technologies are affirming themselves, bringing new challenges for the modelling community. In
addition, the use of monolithic microwave integrated circuits (MMIC) is also increasing, making
necessary the availability, in the circuit design phase, of models which are computationally efficient
and at the same more and more accurate. The importance of modelling is even more evident by
thinking at the wide area covered by microwave systems: terrestrial broadband, satellite communications, automotive applications, but also military industry, emergency prevention systems
or medical instrumentations.
This work contains a review of the empirical modelling approach, providing the description of
some well-known equivalent-circuit and black-box models.
In addition, an original modelling approach is described in details, together with the various
possible applications: modelling of nonquasi-static phenomena as well as of low-frequency
dispersive effects. A wide experimental validation is provided, for GaAs- and GaN-based devices.
Other modelling issues are faced up, like the extraction of accurate models for Cold-FET or the
more convenient choice of the data-interpolator in table-based models.
Finally, the device degradation is also treated: a new measurement setup will be presented, aimed
to the characterization of the device breakdown walkout under actual operating conditions for
power amplifiers.
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Walker, Dominic. "Modelling and characterisation of radar sea clutter." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252414.
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Robbins, Lynda E. "Modelling cryptographic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ31163.pdf.
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Zachariadis, V. "Modelling pedestrian systems." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1435418/.
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The thesis is organised in two parts. The objective of the first part is to review existing approaches to the simulation of microscopic pedestrian movement, to identify weaknesses and to propose an alternative model that addresses some of them. A three-layered classification framework is used to sort models based on their treatment of state-space, action-space and information-space. We identify three critical modelling parameters: the discretisation of the state space, the synchronisation of behavioural action (the cause) and its result (the effect), and the treatment of uncertainty and its impact on behaviour. We continue by presenting a pedestrian micronavigation model, which is driven by two types of actions taking place in distinct spatiotemporal contexts; behavioural actions, applied using a discrete time and action-space platform, and physical actions, triggered in continuous time and space. Finally, we present simulation outputs for simple modelling exercises and demonstrate the flexibility of the proposed modelling framework in tackling scenarios that require more complex decision-making processes. The second part focuses on route choice modelling. We start by discussing the effect of spatial morphology and configuration on pedestrian behaviour and routing decisions. Following the three-layered classification framework that was presented in the first part, we review methods of spatial abstraction and discuss their validity for representing state, action and information spaces for pedestrian routing. We propose a network-based abstraction of space derived from the visibility characteristics. In chapter 10, we address one of the most challenging aspects of pedestrian route-choice modelling: route-assignment under transient traffic conditions. The proposed route-choice models are based on structures that propagate feedback of experienced route costs and system-wide self-learning. This approach is appropriate for two reasons: it facilitates the integration of micro-navigation movement simulation with macroscopic route-choice behaviour modelling, and permits the simulation of variable levels of prior experience.
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Levin, Ari. "Modelling mechanical systems." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/19420.
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Education should be one of the highest priorities of any country. The ability to pass on knowledge and understanding effectively is a sign of a good educational system. From an engineering perspective, better teaching tools allow for greater understanding by the students making them better engineers. Educational aids have been with us for a long time. Inventions from the abacus to the personal computer, have aided engineering students in faster understanding and application of their work. These aids are costly and sometimes become affordable only when outdated and redundant. A low-cost device that does not date would be the educationalist's ideal solution. To this end, a concept model of a conveyor sorting system was developed using Lego as the design medium. The model is a conveyor belt along which coloured blocks are sorted into bins by pneumatic cylinders. The model is controlled by a personal computer and the Lego interface box. The software is written in Visual Basic.
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Somasiri, Nalinda Prasad. "Advanced electromagnetic modelling of multilayer monolithic microwave integrated circuits." Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406933.
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Khraisheh, Majeda Abdel Majeed. "Investigation and modelling of combined microwave and air drying." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387929.
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singh, Ranjit. "Characterisation and modelling of microwave high electron mobility transistors." Thesis, University of Leeds, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702130.
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Kumar, Chandan. "Modelling intermittent microwave convective drying (IMCD) of food materials." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/85437/1/CHANDAN_KUMAR_Thesis.pdf.
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This thesis develops comprehensive mathematical models for an advanced drying technology Intermittent Microwave Convective Drying (IMCD). The models provide an improved physical understanding of the heat and mass transport during the drying process, which will help to improve the quality of dried food and energy efficiency of the process, as well as will increase the ability of automation and optimization. The final model in this thesis represents the most comprehensive fundamental multiphase model for IMCD that considers 3D electromagnetics coupled with multiphase porous media transport processes. The 3D electromagnetics considers Maxwell's equation and multiphase transport model considers three different phases: solid matrix, liquid water and gas consisting water vapour and air. The multiphase transport includes pressure-driven flow, capillary diffusion, binary diffusion, and evaporation. The models developed in this thesis were validated with extensive experimental investigations.
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Holder, David John. "Characterisation and modelling of Heterostructure Bipolar Junction Transistors." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305433.
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Marín, Garcia Jordi. "Off-axis holography in microwave imaging systems." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/285129.
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En las pasadas décadas, la investigación en tecnología de terahercios fue únicamente motivada por instrumentación para los campos de astrofísica y ciencias de la tierra. La principal línea de investigación de estos campos comprende la detección, identificación y mapeo mediante espectroscopia molecular de bandas de emisión y absorción de gases a baja presión. Este campo fue el mayor foco de desarrollo que permitió en primer lugar el desarrollo de instrumentación y tecnología a bandas de terahercios. En contraposición con su uso en campos científicos, la radiación de terahercios es una de las bandas de radio-frecuencia menos usadas en el ámbito comercial. La escasez de fuentes, sensores, sub-sistemas e instrumentos ha dificultado en los últimos años la proliferación de aplicaciones para un mayor público de consumo. La combinación de los últimos avances tecnológicos provenientes del campo científico, así como el descubrimiento de nuevas aplicaciones ha despertado de nuevo el interés por este campo, lo que ha supuesto un nuevo impulso económico para el desarrollo a estas frecuencias tanto a nivel público como privado.
Además del mencionado interés científico, la radiación de terahercios tiene características muy atractivas como por ejemplo una buena resolución espacial (comparada con menores frecuencias), penetración en materiales, capacidades espectroscópicas, absorción por humedad y niveles bajos de energía.
El trabajo desarrollado en esta tesis es parte de un proyecto de investigación a nivel nacional Español denominado Terasense. El interés principal de este proyecto es equipar las instituciones de investigación académicas con un nuevo conjunto de instrumentación y capacidades para poder desarrollar proyectos en el estado del arte en el campo de ondas milimétricas y sub-milimétricas.
El objetivo principal de esta tesis es explorar la viabilidad de sistemas de imagen en microondas y ondas milimétricas basados en técnicas holográficas mediante medidas de intensidad. En este documenta se estudia principalmente el uso de la técnica holográfica con referencia desplazada. No solo desde un punto de vista teórico sino especialmente desde un punto de vista experimental y práctico. En la tesis, diferentes experimentos y dispositivos son simulados, diseñados e implementados. La ida y vuelta entre software y hardware ha permitido la creación de un marco de desarrollo para el test de las diferentes técnicas de imagen estudiadas. El rango de frecuencia escogido como meta para este proyecto es la banda de frecuencia W (75-110 GHz). Sin embargo, muchos experimentos han sido desarrollados primero en banda X (8-12 GHz) para desarrollar la experiencia necesaria requerida para trabajar a frecuencias superiores en el rango de las ondas milimétricas.In past decades research in terahertz technology was solely motivated by instruments for topics such as astrophysics, planetary and earth sciences. Molecular line spectroscopy detection, identification and mapping of thermal emission and absorption signatures from low pressure gases comprised the main focus for most scientific requirements and motivated the development of terahertz instrumentation and technology. In spite of the scientific contributions of terahertz radiation, its spectrum is still one of the least used electromagnetics bands in commercial use. The unavailability of sources, sensors, sub-systems and instruments has been a cumbersome issue over the past years for its wide-spread use in commercial instrumentation. The combination of technological advances coming from the space-based community, along with the emergence of new applications, have managed to drive again the interest from both public and private sectors which has renown and skyrocketed the funding and research in terahertz applications. Aside from the aforementioned scientific interest, terahertz radiation has appealing characteristics such as good imaging resolution (as compared to lower frequencies), material penetration, spectroscopic capabilities, water absorption and low energy levels. The work of this thesis is part of a Spanish national research project called Terasense. The main focus of the project is to equip national academic research institutions with a completely new set of instrumentations and capabilities in order to advance towards the current state of the art in millimeter and sub-millimeter wave technologies. The main objective of this thesis is to explore the viability of microwave and millimeter-wave imaging systems based on intensity-only holographic techniques. This dissertation is mostly focused on the Off-Axis Holography technique. Not only from a theoretical perspective but specially from an actual implementation standpoint. In order to do so, different experimental setups and devices have been designed and manufactured. Iteration between hardware and software has created a framework for devising and testing different imaging techniques under consideration. The frequency range W-Band (75-110 GHz) has been chosen as the main goal for all systems under study, however different setups will first be constructed, characterized and tested at X-Band (8-12 GHz) in order to build up the expertise required to work at millimeter-wave frequencies.
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Niotaki, Kyriaki. "Design of efficient microwave power amplifier systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284935.
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In the future communication systems, it is of key importance that the transceivers are capable of operating in multiple frequency bands and with complex signals. In this context, the power amplifier is a critical component of the transceiver, since it is responsible for most of the total power consumption in base stations and portable devices. Apart from the power consumption, the design of power amplifier systems must account for multi-band/broadband capabilities, high peak-toaverage power ratio signals and the mismatch effect caused by the various operating conditions. Hence, the design of power amplifier topologies that enhance the total system efficiency and reliability is a challenging task.
This PhD dissertation introduces novel power amplifier architectures and solutions for modern communication systems. The contributions of this thesis can be divided in two parts. The first part deals with the study and design of power amplifier systems. It is of major importance that these designs provide linear amplification and operation at multiple frequency bands, which will permit the reduction of the cost and size of the devices. Additionally, we investigate the possibility to harvest the dissipated power from the power amplification process. For the development of the prototypes, lumped-element topologies, transmission line implementation and Substrate Integrated Waveguide (SIW) technology are adopted.
In the second part of the thesis, novel matching networks are introduced and their properties are studied. In particular, resistance compression topologies are proposed to overcome the performance degradation associated with the sensitivity of nonlinear devices to environmental changes. These networks can be adopted in modern power amplifier architectures, such as envelope tracking and outphasing energy recovery power amplifier topologies, in order to provide improved performance over a wide range of operating conditions.Es primordial que los transceptores de los futuros sistemas de comunicación sean capaces de operar en múltiples bandas de frecuencia y con señales complejas. En este contexto, el amplificador de potencia es un componente crítico del transceptor dado que su consumo energético supone la mayor parte del consumo tanto de las estaciones base como de los dispositivos móviles. Aparte del consumo energético, los nuevos diseños de sistemas de amplificación de potencia deben considerar aspectos como la capacidad de operar en múltiples bandas o en banda ancha, el uso de señales con alta relación de potencia pico a potencia media (PAPR) y el efecto de desadaptación que aparece bajo las diferentes condiciones de funcionamiento. Por lo tanto, el diseño de nuevas topologías para amplificadores de potencia que mejoren la eficiencia total del sistema y la fiabilidad es una tarea compleja. Esta tesis doctoral presenta nuevas arquitecturas de amplificadores de potencia y soluciones para los sistemas de comunicación modernos. Las contribuciones de esta tesis se pueden dividir en dos partes. La primera parte se centra en el estudio y diseño de sistemas de amplificación de potencia con el fin de proporcionar amplificación lineal y funcionamiento en múltiples bandas de frecuencia, lo que permitirá reducir el coste y tamaño de los dispositivos. Además, se investiga la posibilidad de reutilizar la energía disipada en el proceso de amplificación de potencia. Para el desarrollo de los prototipos, se utilizan topologías hibridas, implementaciones con líneas de transmisión y tecnología de guía de onda integrada en sustrato (SIW). En la segunda parte de la tesis, se proponen redes de adaptación y se estudian sus propiedades. En particular, se proponen topologías de compresión de resistencia para minimizar el efecto que producen en el rendimiento la sensibilidad de los dispositivos no lineales a los cambios ambientales. Estas redes pueden ser utilizadas en arquitecturas modernas de amplificadores de potencia como pueden ser las topologías envelope tracking y outphasing energy recovery con el fin de proporcionar un rendimiento mejorado bajo múltiples condiciones de funcionamiento.
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Petersson, Magnus. "Microstrip Solutions for Innovative Microwave Feed Systems." Thesis, Linköping University, Department of Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1034.
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This report is introduced with a presentation of fundamental electromagnetic theories, which have helped a lot in the achievement of methods for calculation and design of microstrip transmission lines and circulators. The used software for the work is also based on these theories.
General considerations when designing microstrip solutions, such as different types of transmission lines and circulators, are then presented. Especially the design steps for microstrip lines, which have been used in this project, are described. Discontinuities, like bends of microstrip lines, are treated and simulated. There are also sections about power handling capability of microstrip transmission lines and different substrate materials.
In the result part there are computed and simulated dimensions of the microstrip transmission lines used in the prototype system. Simulations of conceivable loads in the cavity illustrate quantitatively the reflection coefficient. Even practical measurements are made in a network analyzer and are presentedin this part.
Suitable materials and dimensions for the final microwave feed transmission line system for high powers are then presented. Since circulators are included in the system a basic introduction to the design of these in stripline and microstrip techniques is also made.
At last conclusions, examinations of the designed system and comparisons to the today’s systems are made.
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Grice, Della Diane. "Microwave effects in condensed phase chemical systems." Thesis, University of Hull, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397082.
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Bashri, Mohd Saiful Riza. "Wearable devices for microwave head diagnostic systems." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33243.
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Although current head imaging technologies such as magnetic resonance imaging (MRI) and computed tomography (CT) are capable of providing accurate diagnosis of brain injuries such as stroke and brain tumour, they have several limitations including high cost, long scanning time, bulky and mostly stationary. On the other hand, radar-based microwave imaging technology can offer a low cost, non-invasive and non-ionisation method to complement these existing imaging techniques. Moreover, a compact and wearable device for microwave head imaging is required to facilitate frequent or real-time monitoring of a patient by providing more comfort to the patient. Therefore, a wearable head imaging device would be a significant advantage compared to the existing wideband microwave head sensing devices which typically utilise rigid antenna structure. Furthermore, the wearable device can be integrated into different microwave imaging setups such as real-time wearable head imaging systems, portable systems and conventional stationary imaging tools for use in hospitals and clinics. This thesis presents the design and development of wearable devices utilising flexible antenna arrays and compact radio frequency (RF) switching circuits for wideband microwave head imaging applications. The design and characterisation of sensing antennas using flexible materials for the wearable head imaging device are presented in the first stage of this study. There are two main variations of monopole antennas that have been developed in this research, namely trapezoidal and elliptical configurations. The antennas have been fabricated using different flexible substrate materials such as flexible FR-4, polyethylene terephthalate (PET) and textile. Wideband performances of the antennas have been achieved by optimising their co-planar waveguide feeding line structures. Importantly, the efficiencies of the fabricated antennas have been tested using a realistic human head phantom by evaluating their impedance matching performances when operating in close proximity to the head phantom. The second stage of the study presents the development of wearable antenna arrays using the proposed flexible antennas. The first prototype has been built using an array of 12 flexible antennas and a conformal absorbing material backed with a conductive sheet to suppress the back lobe radiation of the monopole antennas. Additionally, the absorber also acts as a mounting base to hold the antennas where the wearable device can be comfortably worn like a hat during the measurement and monitoring processes. The effect of mutual coupling between adjacent antennas in the array has been investigated and optimised. However, the use of the absorbing material makes the device slightly rigid where it can only be fitted on a specific head size. Thus, a second prototype has been developed by using a head band to realise a stretchable configuration that can be mounted on different sizes of human heads. Furthermore, due to the stretchable characteristic of the prototype, the antennas can be firmly held in their positions when measurements are made. In addition, fully textile based sensing antennas are employed in this prototype making it perfectly suitable for monitoring purposes. Low cost and compact switching circuits to provide switching mechanism for the wearable antenna array are presented in the third stage of this study. The switching circuit is integrated with the antenna array to form a novel wearable microwave head imaging device eliminating the use of external bulky switching network. The switching circuit has been built using off-the-shelf components where it can be controlled wirelessly over Bluetooth connection. Then, a new integrated switching circuit prototype has been fabricated using 6-layer printed circuit board (PCB) technology. For the purpose of impedance matching for the radio-frequency (RF) routing lines on the circuit, a wideband Microstrip-to-Microstrip transition is utilised. The final stage of this study investigates the efficacy and sensitivity of the proposed wearable devices by performing experiments on developed realistic human head phantoms. Initially, a human head phantom has been fabricated using food-based ingredients such as tap water, sugar, salt, and agar. Subsequently, lamb's brains have been used to improve the head phantom employed in the experiments to better mimic the heterogeneous human brain. In terms of imaging process, an interpolation technique developed using experimental data has been proposed to assist the localisation of a haemorrhage stroke location using the confocal delay-and-sum algorithm. This new technique is able to provide sensible accuracy of the location of the blood clot inside the brain. The wearable antenna arrays using flexible antennas and their integrations with compact and low cost switching circuits reported in this thesis make valuable contribution to microwave head imaging field. It is expected that a low-cost, compact and wearable radar-based microwave head imaging can be fully realised in the future for wide range of applications including static scanning setup in hospitals, portable equipment in ambulances and as a standalone wearable head monitoring system for remote and real-time monitoring purposes.
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Alhossin, Saad Mohamed. "Novel antenna design for microwave RFID systems." Thesis, University of Newcastle upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548001.
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Strawser, Richard E. "MEMS Electrostatic Switching Technology for Microwave Systems." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin974746046.
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Sanga, Essau C. M. "Microwave assisted drying of composite materials : modelling and experimental validation." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38271.
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Model materials with discretely varying loss factors under microwave fields, were studied with respect to drying characteristics. In the first part numerical simulations were conducted to study the fluid flow and heat transfer in a rectangular microwave cavity where cylindrical samples were heated by microwave. The Reynolds numbers studied in this work were 2800, 5600 and 11200 based on the entrance diameter to the rectangular microwave cavity. Heat transfer results in terms of Nusselt numbers for the Reynolds number ranges studied are presented and discussed.In the second part of the study a mathematical model was developed to describe heat and mass transfer of a model material under microwave fields. The dynamic temperature and moisture profiles of cylindrical composite samples subjected to microwave and convective energy were determined and validated at microwave power density levels of 0.20 W/g, 0.3 W/g and 0.4 W/g based on initial weight of the sample. Model results were compared with experimental data and found to agree within 1.0--2.6%. Predicted temperature profiles at selected locations within the model material were also showed a good agreement with experimental data. However, a significant discrepancy between the numerical and experimental temperature results occurred after t > 30 minutes. This might have been due to localized overheating, or to mathematical model overestimation.
Lastly, a quality evaluation of the dried samples was also performed. Quality attributes evaluated were surface color, shrinkage and rehydration capacity. Samples dried as a special case of biological material were of better quality when compared to other samples.
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Taylor, Melita Clare. "Modelling the microwave transmission of metal arrays using modal matching." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3543.
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This work explores the interaction of electromagnetic radiation with periodic metal-dielectric composite materials. In particular, the majority of the studies explore the role of evanescent diffraction in the regime where the wavelength of the incident radiation is of the order of the period of the array just below the onset of diffraction. The underlying aim of the thesis is to build on the current knowledge and gain deeper understanding into the causal mechanism of the electromagnetic response of these periodic materials. Developments in metamaterial research have led to a resurgance of interest in the use of periodic metallic surface to control the transmission of electromagnetic radiation. The response of these surfaces can be `tuned' to provide the required response simply by altering the geometric parameters of the material. Numerical modelling techniques are often used to predict the response of such structures. However, the aim of this work is to gain a deeper understanding of the reasons for the response and therefore an analytical modal matching method has been used. The modal matching method provides the opportunity to extract greater understanding of the resonant phenomena by linking them to specific mathematical terms in the analytical formulation. The modal matching technique is initially used to study the response from a single layer bigrating comprising a square array of square holes in a PEC sheet and its complementary system of a square array of square PEC patches. The importance of evanescent diffraction in both resonant phenomena and tunneling responses is discussed and it is shown that complete transmission (reflection) is supported by these structures even for very high (low) metal occupancy. This technique is extended and adapted to describe a variety of structures in chapters 5 and 6, exploring how resonant excitation of surface waves via evanescent diffraction leads to highly interesting electromagnetic responses. In chapter 7, alternating multilayer stacks of two different subwavelength meshes provide an observable one-dimensional topological mode in a physical system for particular mesh configurations.
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Joelsson, Andreas, and Jonathan Ohlsson. "Indoor propagation modelling at microwave frequencies in a server environment." Thesis, Linköpings universitet, Fysik och elektroteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119980.
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The Link¨oping site is the first of Ericsson’s three information and communication technology centres. This facility will house the company’s complete portfolio and use the latest cloud technology in order to enable the research and development engineers to more efficiently test and develop new technologies. In the test lab environment there is a high capacity microwave telecommunication system called MINI-LINK. These systems operate at much higher frequencies than more traditional telecommunication systems. In the test lab these systems are communicating with a cable interface instead of its intended air interface. The purpose of this thesis is to evaluate the potential leakage of this system in the test lab environment. The evaluation of the leakage in the test lab is done by developing an empirical path loss model for the desired frequencies used by the equipment in the test lab. This model is later implemented in a leakage simulation tool designed in Matlab, which simulates and displays the leakage power in a 2D plane. This report mainly focuses on the process of determining the constants and the implementation of the path loss model.
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Desai, Renoo. "Transmission line modelling of heating in a domestic microwave oven." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303126.
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Xue, Hongxi. "Modelling and analysis of GaAs dual gate MESFETS microwave mixers." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238153.
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Bunting, Jeremy. "The modelling and measurement of noise in microwave FET oscillators." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254670.
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Holmström, Patrik. "Modelling manufacturing systems capability." Licentiate thesis, KTH, Production Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4054.
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Any way of making the manufacturing industry more efficient is always of great interest due to the contribution of manufacturing to the society. A major asset within manufacturing is information about manufacturing systems, as a base when making decisions. The most essential information within manufac-turing industry would be the manufacturing systems capability information. That information would include information about the resource, used process and produced product. Although important, manufacturing systems capability models are rare, and the information seems to be challenging to model.
The purpose of this thesis is to model manufacturing systems capability with focus on the machining industry.
In order to model manufacturing system capability, existing information standards has been used as a frame of reference. Some information standards have been evaluated on industrial cases and sometimes modified to serve a specific purpose. The information standards have been evaluated to first separately represent product, process and resource. Thereafter have the infor-mation standards been evaluated to represent all three domains together.
ISO10303-214 (AP214) has been modified and evaluated to represent any process within manufacturing. The state of the product and the state of used manufacturing system are described and connected to every relevant process step.
AP214 with ISO10303-224 (AP224) has been used together with a developed method, to describe manufacturing system capability within machining. Within the limitations of AP224 geometrical feature description, the capability of a manufacturing system can be defined and connected to a product description. Using similar feature based description for the capability and the product description, products manufacturability can be evaluated.
Also ISO14649 and ISO10303-238, both also known as STEP-NC, are treated in this thesis as enablers to describe manufacturing system capability. STEP-NC is shown to describe manufacturing systems within machining where the product, process and resource are collectively described. In order to describe capability and evaluate products manufacturability, STEP-NC has to be extended from describing/modelling one configuration of a manufacturing system to describe a set of configurations.
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Holmström, Patrik. "Modelling manufacturing systems capability /." Stockholm : Royal Institute of Technology, Industrial Engineering and Management, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4054.
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Bateman, Nicola. "Modelling manufacturing systems flexibility." Thesis, De Montfort University, 1998. http://hdl.handle.net/2086/10678.
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The flexl.bility to change product and processes quickly and economically represents a significant competitive advantage to manufacturing organisations. The rapid rise in global sourcing, has resulted in manufacturers having to offer greater levels of customisation, thus a wider product range is essential to an organisation's competitiveness. The rate at which new products are introduced to the market has also increased, with greatly reduced development times being essential to a new product's market success. Hence there is a strong need to have a flexible manufacturing system such that new products may be introduced rapidly. These drivers have made the need for flexibility within manufacturing systems of great importance. However, there are many types of flexibility and to ensure that organisations correctly target these types of flexibility there is a need to measure fleXlbility, because, measuring fleXlDility allows manufacturers to identify systems which will improve their performance. This research, therefore, has focused on the development measures for two types of flexibility ie. mix fleXlDility and product flexibility. These represent the ability to change between the manufacture of current products i. e. mix flexibility and the ability to introduce new products i.e. product fleXlDility. In order to develop effective measures for these types of fleXlbility a conceptual model has been developed, which represents the current and potential future product range of manufacturing systems. The methodology developed for measuring mix and product flexibility has been successfully applied in two companies. These companies represent diverse manufacturing environments. One operates in high volume chemical manufacture and the other in low to medium volume furniture manufacture. Through applying this methodology in these two companies it has been demonstrated that the methodology is generic and can be used in a wide range of companIes.
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Su, Xiangyao. "Modelling of pharmaceutical systems." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241495.
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Duan, Zhenhua. "Modelling of hybrid systems." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242213.
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Tarokh, M. J. "Systems reliability performance modelling." Thesis, University of Bradford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715427.
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Kelso, Margaret Black. "A study of the use of combined thermal and microwave modelling of body regions for microwave thermography." Thesis, University of Glasgow, 1995. http://theses.gla.ac.uk/1107/.
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Microwave thermography has been used for the objective assessment of inflammation in the knee joints and wrist and finger joints of patients suffering with rheumatoid arthritis by comparison with similar information obtained from a control group of subjects. Combined microwave and thermal modelling has been used to estimate the effective blood supply to the anterior intra-articular region of the patella, and the perfusion of the quadriceps muscle in both groups. 2-D numerical modelling was compared with results obtained using 1-D modelling. Microwave thermography has also been used for the detection of breast cancer. However, problems such as high false positive detection rates have occurred due to natural cyclical breast temperature changes. The thermal behaviour of the normal breast throughout the menstrual cycle has been investigated and it is shown that microwave thermography is capable of detecting temperature variations in the female breast corresponding to the ovulatory and luteal phase of the menstrual cycle. Combined microwave and thermal modelling estimated the effective perfusion of the normal breast to be in the range 0.2 - ˜ 2 kg m-3s-1. This is consistent with previous work. Microwave thermography is a quick, simple technique which clinicians can easily use. It is non-invasive, passive and causes the patient no distress. By using combined microwave and thermal modelling it is possible to estimate tissue blood perfusions and water contents and compare them with expected values. The technique has many potential applications and will hopefully find a secure niche in clinical medicine.
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Srivastava, Y. "Large signal modelling of coupled-cavity travelling wave tubes." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379740.
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McDowall, David Stewart. "Concurrent mixed mode modelling of active strip antennas." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239014.
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Malan, Daniel Hugo. "Parallel finite element analysis for microwave heating systems." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621900.
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Lees, Jonathan. "Doherty amplifier structures for modern microwave communication systems." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56074/.
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The Power Amplifier (PA) is a critical component in any mobile communications system with performance that is very sensitive to RF envelope dynamics. Achieving the required linearity demanded by evolving communications systems invariably involves increasing PA complexity at the cost of reducing PA efficiency the consequences of which are severe and include for example reduced operational time for portable communications devices and perhaps less obviously the significant running, capital and thermal management costs associated with mobile communication system base-stations. The Doherty PA is one of a number of elegant architectures that have been developed to address this problem, and although conceived and patented in the 1930's, has only recently become established as a means of enhancing efficiency in microwave PA applications. The Doherty is renowned for its elegant simplicity however, the realisation of functional Doherty PAs using modern microwave devices is problematical and hindered by many hidden complexities, which are in general brought about by the complex, 'load-pulling' action of two active devices that conspire to cause a variety of performance related problems. Although harmonic behaviour is important, understanding device interaction at a fundamental level has been found to be the critical factor in achieving good overall Doherty performance. With this in mind, this thesis concentrates initially on developing an extensive understanding of fundamental device interaction through the use of a novel Doherty measurement approach which involves replacing the classical Doherty's symmetrical input power division arrangement with independent, phase-coherent excitations. The resulting insight has meant that it has been possible to introduce more focused measurement techniques including harmonic analysis and waveform engineering in order to further explore individual device behaviour. The extensive use of harmonic load-pull measurement systems and the direct synthesis of the impedance environments that exist within the Doherty have allowed a number of device technologies to be considered within the application environment resulting in the realisation of GaAs and GaN Doherty prototypes. As a direct result of this analysis, a number of optimisation approaches have been identified that involve the dynamic adjustment of relative input magnitude, relative input phase and relative device bias, which has in turn exposed the various design trade-offs that exist between linearity and efficiency within the Doherty. Other work includes the development of modulated measurement systems and specialised excitations that allow the meaningful comparison between measured single-tone and modulated performance, as well as allowing more comprehensive investigations into Doherty linearity under varying IF impedance conditions.