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Experimentální bezdrátový spoj v kmitočtovém pásmu 60 GHz
Lambor, Jiří ; Polívka, Milan (oponent) ; Raida, Zbyněk (vedoucí práce)
Práce se zabýva problematikou spojů v kmitočtovém pásmu 60 GHz. V této oblasti je vykazován vysoký útlum atmosférou způsobený rezonancí molekul kyslíku. Toho může být využito pro oddělení jednotlivých vytvořených sítí. V dokumentu jsou porovnány dostupné transceivry několika výrobců. Dále je práce zaměřena na návrh, simulaci a výrobu soustavy napáječe a antény pracující na kmitočtu 60 GHz. Trychtýřová anténa je navrhunta na technologii SIW
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Speciální reflektory pro širokopásmové dipólové antény
Velička, Pavel ; Goňa, Stanislav (oponent) ; Raida, Zbyněk (vedoucí práce)
Práce pojednává o speciálních vlnitých reflektorech pro širokopásmové antény. Vlnité reflektory jsou rozděleny na typ H a typ E. Z těchto typů je následně vytvořena jejich kombinace. Všechny tři typy reflektorů byly simulovány a následně analyzovány. Dále se práce zabývá různými druhy širokopásmových dipólů, které jsou postupně umísťovány nad zkoumané reflektory. Takto vytvořené reflektorové antény jsou pak porovnávány. U antén s nejlepšími parametry pak simulujeme přenos mezi dvěma anténami. Všechny simulace byly provedeny v programu CST Microwave Studio. Vybrané antény byly realizovány a změřeny. Následnými simulacemi jsme zjišťovali příčiny rozdílů mezi simulovanými a měřenými výsledky.
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Antennas for Wireless Body Area Networks
Hebelka, Vladimír ; Schejbal, Vladimír (oponent) ; Vrba,, Jan (oponent) ; Raida, Zbyněk (vedoucí práce)
The dissertation thesis is focused on the proposing a general synthesis approach to the design of the antenna operating in proximity of human body models. The critical parameters comprise the antenna impedance matching, polarization properties and radiation patterns. The elementary investigation is done on simplified human body models, where we strictly define material properties. For advanced simulations, we have to consider more details in the model. Simulations are confronted with the measurement on real saples. In This thesis we will include the problems of interaction between an antenna and a human body.
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Probabilistic Neural Networks for Special Tasks in Electromagnetics
Koudelka, Vlastimil ; Tučková,, Jana (oponent) ; Hartnagel, Hans Ludwig (oponent) ; Raida, Zbyněk (vedoucí práce)
The thesis deals with behavioural modelling techniques capable solving special tasks in electromagnetics which can be formulated as approximation, classification, probability estimation, and combinatorial optimization problems. Concept of the work lies in applying a probabilistic approach to behavioural modelling. Examined methods address two general problems in machine learning and combinatorial optimization: ”bias vs. variance dilemma” and NP computational complexity. The Boltzmann machine is employed to simplify a complex impedance network. The Parzen window is regularized using the Bayesian strategy for obtaining a model selection criterion for probabilistic and general regression neural networks.
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Textile Integrated Waveguide Components
Cupal, Miroslav ; Polívka, Milan (oponent) ; Joler, Miroslav (oponent) ; Raida, Zbyněk (vedoucí práce)
The thesis is focused on the research of structures based on the Textile Integrated Waveguide (TIW). Attention is turned to the electrical characterization of textile materials (textile substrates, yarns) to be used for the implementation of textile-integrated antennas, reconfigurable and active circuits. The thesis deals with the design of multilayer transitions between a microstrip line on a conventional substrate and textile-integrated lines. Second, a concept of the textile-integrated switch is presented. The switch is controlled by conductive posts which are connected or disconnected by DC driven PIN diodes to form open or closed walls. Finally, the design methodology for textile-integrated circularly polarized antennas operating in ISM bands up to 24 GHz is proposed. All the design procedures were verified by simulations and measurements of real samples manufactured by screen-printing using a silver polymer paste. For bonding semiconductor components, conductive silver adhesives were used. Screen-printed components were compared with reference structures manufactured from a self-adhesive copper foil.
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Terahertz Antenna Arrays for Communications
Warmowska, Dominika ; Joler, Miroslav (oponent) ; Pokorný, Michal (oponent) ; Raida, Zbyněk (vedoucí práce)
The thesis is focused on the research of THz antenna arrays to be used for communications. Attention is turned to modeling metallic surfaces at THz frequencies, a proper characterization of gold conductivity, its relation to Drude model and corresponding measurements. Moreover, the best methods for modeling thin metallic layers (depending on the skin depth related to the metal thickness) are presented. An optimized element of a THz 2×2 antenna array designed for the application of communications is developed in a way that enables an expansion to a larger array. The expansion ability is demonstrated on a 4×4 antenna array which is presented in the thesis too. The designed antennas achieve parameters better than the state-of-art antennas. The presented antennas radiate circularly polarized wave at THz frequencies, operate in a wide bandwidth, have a high gain and are of a compact size. In the thesis, an 8×8 antenna array with a beam steering capability is presented. The main beam of the antenna array can be controlled in two dimensions. A high gain of the radiated circularly-polarized wave can be achieved that way. Different approaches to modeling antennas with thin metallic layers are compared and the best methods are recommended from the viewpoint of different requirements. The designed 2×2 and 4×4 antenna arrays are manufactured using a microfabrication technology. Each step of the fabrication is described in detail and discussed. The reflection coefficient at the input of antennas is measured and compared with simulations. Discrepancies in results are associated with surface roughness which is analyzed by a scanning probe microscope and a scanning electron microscope. By down-scaling the developed THz antenna, a low-profile high-gain antenna for Ka-band space applications is designed. The presented antenna achieves better results than state-of-art CubeSat antennas. The antenna performance is verified by a prototype to be operated at 9 GHz, and the radiation characteristics are experimentally confirmed.
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Aktivní anténa se zdvojovačem kmitočtu
Tomíček, Martin ; Černý, Petr (oponent) ; Raida, Zbyněk (vedoucí práce)
Tato práce je zaměřena na analýzu planární antény pracující na dvou kmitočtech s využitím zdvojovače kmitočtu. Je zde popsán návrh antény i její modelování v programu ANSOFT Designer. Je zde kladen požadavek, aby pracovní frekvence byly 900 MHz a 1,8 GHz a aby anténa pracovala s vidy TM10 a TM01.
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Finite Element Time Domain and Its Applications
Cigánek, Jan ; Dědková, Jarmila (oponent) ; Karban, Pavel (oponent) ; Raida, Zbyněk (vedoucí práce)
The thesis deals with modeling dispersive media by the finite-element time-domain method. Mathematical model including dispersive models is proposed and finite element approximation of this model is presented. Three of the most commonly used dispersive models are investigated, namely the Debye model, the Lorentz model and the Drude model. The techniques for implementing these dispersive models are described. Presented techniques are incorporated into a finite element method. Finally, a new method based on a digital filtering technique is presented. Various test examples are used to verify all the developed methods. Achieved results are discussed, and possible improvements of methods are suggested.
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Antenna Arrays with Synthesized Frequency Response of Gain
Všetula, Petr ; Polívka,, MIlan (oponent) ; Bonefačic, Davor (oponent) ; Raida, Zbyněk (vedoucí práce)
In the thesis, we present a method of the synthesis of a dipole antenna array with prescribed spectral and spatial filtering capabilities. Thanks to the spatial filtering capabilities, the main lobe direction and the value of gain vary negligibly over the operating band. Thanks to the spectral filtering capabilities, the value of gain is maximal in the operating band and minimal out of the operating band. In order to synthesize a dipole array with prescribed filtering capabilities, amplitudes, phases and dimensions of antenna elements are optimized. The initial optimization is speeded up by considering an idealized antenna array when evaluating objective functions. Since the optimization comprises requirements on the main lobe direction, the value of gain and impedance matching, a multi-objective optimization is used. The optimized antenna array is analyzed by a full-wave simulator to verify results of the synthesis. Finally, the synthesized dipole array is manufactured and its performance is experimentally verified.
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Tištěné nositelné antény
Trubák, Jan ; Láčík, Jaroslav (oponent) ; Raida, Zbyněk (vedoucí práce)
Ve své práci se zabývám návrhem planární antény na textilním substrátu. Anténa pracuje na frekvenci 5,8 GHz. Parametry vyrobené antény porovnávám s charakteristikami nasimulovanými v programu ANSYS HFSS a snažím se dosáhnout co nejlepší shody počítačového modelu s reálnou anténou měřením relativní permitivity textilního substrátu, výpočtem optimálních rozměrů motivu planární antény a vhodnými úpravami simulace.
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