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Transmitting antenna with dual circular polarisation for indoor antenna measurement range
Mrnka, Michal ; Hazdra, Pavel (referee) ; Raida, Zbyněk (advisor)
The purpose of the thesis is to design transmitting antenna based on septum polarizer solution for indoor measurement range. The antenna is considered for both senses of circular polarization. The design is divided into three main sections. First section is devoted to analysis and selection of a suitable waveguide. Ridge waveguide as a crucial part of a septum polarizer is mentioned in this section. Second part is the most critical; here the septum polarizer is analyzed and based on simple procedure also designed. Two suitable horn apertures are then developed as a part of the third section. Individual transmitting antenna parts are assembled together into one model and simulated with excellent results for axial ratio, cross-polarization discrimination, return loss and isolation between ports.
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Antenna system for car radar
Zechmeister, Jaroslav ; Hazdra, Pavel (referee) ; Láčík, Jaroslav (advisor)
This thesis deals with the design of lens antennas for automotive radar in 77 GHz bandwidth. The work explains methods of designing waveguides as well as horn antennas and dielectric lens. A simulation of three designed horn antennas is performed in CST Microwave Studio. Antennas with spherical and hyperbolical lens are simulated as well and subsequently optimized for maximal gain. The thesis also investigates effects of the lens permittivity on its properties. Furthermore, the work deals with a design of an antenna system with minimalized antenna coupling. Nylon, ABS and photopolymer lens are designed and compared afterwards. ABS and photopolymer lens were produced by 3D print
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Planar fractal filter on defected ground substrate
Kufa, Martin ; Hazdra, Pavel (referee) ; Raida, Zbyněk (advisor)
The diploma thesis is focused on the design of planar filters combining fractal layouts and defected ground substrates. The diploma thesis can be divided into three main parts. First, basic knowledge about fractals is presented (creation of Minkowski Island and Koch loop, e.g.). Then, the principle of defected ground structure is described, and a combination of fractal motives with a defected ground structure is briefly introduced. Properties of investigated structures are verified by CST Microwave Studio and Ansoft HFSS. Second, different defected ground structures under the 50 transmission line are designed, and conventional equivalent filters are created. Filters are simulated and compared. In final, the investigated filters are recalculated for the substrate Arlon 25N, simulated, manufactured, measured and confronted with a conventional filter on the defected ground substrate.
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Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers
Voves, J. ; Pošta, A. ; Davydova, Marina ; Laposa, A. ; Povolný, V. ; Hazdra, P. ; Lambert, Nicolas ; Sedláková, Silvia ; Mortet, Vincent
Epitaxial growth of diamond is critically important for the fabrication of diamond-based electronic devices. The emerging study of the epitaxial diamond growth on the (113) vicinal surfaces evidences highly needed high growth rates and low structural defects concentrations with both p- and n-type doping. In this work, we compare the morphology and dopant concentration incorporation of heavily boron-doped (113) epitaxial diamond layers with conventionally studied (100) and (111) epitaxial layers. Epitaxial layers were grown using resonance cavity Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) system. The surface morphology of epitaxial layers was studied by optical microscopy and atomic force microscopy, whereas the boron incorporation homogeneity was determined by Raman spectroscopy mapping.
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Structure defects in SiC radiation detectors
Zetek, Matyáš ; Belas, Eduard (advisor) ; Hazdra, Pavel (referee)
Silicon carbide (SiC), is a wide band gap (2.4 eV < Eg < 3.3 eV) semiconducting material well known for its potential applications in high-temperature, high-power, high-frequency or hard radiation resistant devices. In this thesis, we are broadening elementary knowledge about this material. We identify energy levels in the material, using Photo-Hall effect spectroscopy supported by the temperature dependency of classic Hall effect measurement and temperature dependent photoluminescence. This knowledge is essential to allow SiC application as a radiation detector.
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Charge transport in semiconducting radiation detectors
Pipek, Jindřich ; Belas, Eduard (advisor) ; Hazdra, Pavel (referee)
This thesis is focused on study of charge transport in semiconducting radiation detectors. Theoretical calculations of current waveforms based on continuity equation and drift-diffusion equation are done. Useful approximations of current waveforms for detector with shallow electron trap are discussed. Monte Carlo simulation of the current waveforms is proposed and applied to fit experimental current waveforms measured using laser-induced transient current technique and for evaluation of charge transport parameters of the detector such as electric field profile, trapping and detrapping time of traps, drift mobility and other parameters. Detectors prepared from semi-insulating GaAs and CdZnTe single crystals are tested using electrical, spectroscopic and optical characterization techniques.
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Antenna system for car radar
Zechmeister, Jaroslav ; Hazdra, Pavel (referee) ; Láčík, Jaroslav (advisor)
This thesis deals with the design of lens antennas for automotive radar in 77 GHz bandwidth. The work explains methods of designing waveguides as well as horn antennas and dielectric lens. A simulation of three designed horn antennas is performed in CST Microwave Studio. Antennas with spherical and hyperbolical lens are simulated as well and subsequently optimized for maximal gain. The thesis also investigates effects of the lens permittivity on its properties. Furthermore, the work deals with a design of an antenna system with minimalized antenna coupling. Nylon, ABS and photopolymer lens are designed and compared afterwards. ABS and photopolymer lens were produced by 3D print
|
|
|
Transmitting antenna with dual circular polarisation for indoor antenna measurement range
Mrnka, Michal ; Hazdra, Pavel (referee) ; Raida, Zbyněk (advisor)
The purpose of the thesis is to design transmitting antenna based on septum polarizer solution for indoor measurement range. The antenna is considered for both senses of circular polarization. The design is divided into three main sections. First section is devoted to analysis and selection of a suitable waveguide. Ridge waveguide as a crucial part of a septum polarizer is mentioned in this section. Second part is the most critical; here the septum polarizer is analyzed and based on simple procedure also designed. Two suitable horn apertures are then developed as a part of the third section. Individual transmitting antenna parts are assembled together into one model and simulated with excellent results for axial ratio, cross-polarization discrimination, return loss and isolation between ports.
|
|
|
Planar fractal filter on defected ground substrate
Kufa, Martin ; Hazdra, Pavel (referee) ; Raida, Zbyněk (advisor)
The diploma thesis is focused on the design of planar filters combining fractal layouts and defected ground substrates. The diploma thesis can be divided into three main parts. First, basic knowledge about fractals is presented (creation of Minkowski Island and Koch loop, e.g.). Then, the principle of defected ground structure is described, and a combination of fractal motives with a defected ground structure is briefly introduced. Properties of investigated structures are verified by CST Microwave Studio and Ansoft HFSS. Second, different defected ground structures under the 50 transmission line are designed, and conventional equivalent filters are created. Filters are simulated and compared. In final, the investigated filters are recalculated for the substrate Arlon 25N, simulated, manufactured, measured and confronted with a conventional filter on the defected ground substrate.
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