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Diffraction on Spatial and/or Deep Objects
Hrabec, Aleš ; Petráček, Jiří (referee) ; Kotačka, Libor (advisor)
This discourse deals with a theoretical study of the radiation passage through a diffraction screen with non-zero size in the propagation direction of the radiation, i.e. the radiation passage through a three-dimensional object. Without any loss of generality, we solve the problem for cylindrical cavity in metal. The task exceeds evidently standard scalar theory of diffraction, thus we solve the problem using a waveguiding theory. Following the principles of the electromagnetic theory, we derive required formulae to determine mode distribution at the entry of the cavity. Further, we solve numerically the radiation propagation through the cavity, then we actually seek for radiation distribution at the very end of the cavity. This yields, with a help of the discrete Fourier transform, an intensity distribution of Fraunhofer diffraction pattern, consequently compared with an intesity distribution of the radiation pattern of Fraunhofer diffraction on infinitely thin circular opening having the radius of the cylinder cavity under study. A comparison of such patterns results to a conclusion, that the cavity length has a significatn influence on the diffraction pattern and more importantly, that the scalar diffraction theory appears incorrect for a coherent light passage through cavities longer than their radius squared. Similarly, the same conclusion is inversely proportional to a wavelength of the interacting radiation. Finally, we mention an existence of the so called "focal regime", when the radiation repeatedly exhibits roughly one order increased intensity on the symmetry axis of the cavity.
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Half-mode substrate integrated waveguide horn antenna
Černý, Matěj ; Mikulášek, Tomáš (referee) ; Láčík, Jaroslav (advisor)
This thesis is about technology of half-mode substrate integrated waveguide (HMSIW) and options proposal of horn antenna fouden on this technology. Based on gained findings HMSIW horn antenna was modeled in program CST Microwave Studio. Main attention is focused on impact geometrical parameters of antenna on it´s emitting and on reflecting ratio at the entrance of antenna. Achieved gain of main lobe was 6 dBi, which is misalignmented to required direction of angle 30°. Antenna has a working frequency 10 GHz.
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Substrate integrated waveguide filter
Vyskočil, Jiří ; Tkadlec, Roman (referee) ; Láčík, Jaroslav (advisor)
In this thesis is discussed a filter design of a band-pass substrate integrated waveguide filter on the frequency of 5 GHz. It also includes design theory, filter synthesis, filter analysis in the program CST Microwave Studio® and the results of measurement on a vector network analyzer. The analysis results are compared with the measured results. Good agreement between simulated and measured results is observed.
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Network for high-frequency on-body communication
Halas, David ; Láčík, Jaroslav (referee) ; Kokolia, Martin (advisor)
This work focuses on the design of a network for high-frequency communication on the human body. The thesis is focused on the design of two-band antennas, namely 2.4 GHz and 5.8 GHz. The antenna is integrated into the textile and works close to the human body. The introduction describes the problem of spreading electromagnetic waves along the human body. Further, the thesis deals with the applicability of different types of antennas for integration on the textile substrate. Based on the simulations performed, a suitable antenna is selected for the purpose. The simulation program used is the CST Microwave Studio. In the end, the antennas were optimized, subsequently manufactured and their parameters measured.
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Textile waveguide
Pelikán, Michal ; Schejbal, Vladimír (referee) ; Raida, Zbyněk (advisor)
Diploma thesis is focused on manufacturing process of waveguide filter. Thesis is divided to 8 chapters. There is summarized theory of possible execution of waveguide filter, used materials, their influence and risks during production. Then are described possible steps of realization and necessary relations for its design, simulation and also practical realization. At conclusion are summarized, compared and described reached results.
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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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Time domain edge finite elements
Cigánek, Jan ; Motl, Milan (referee) ; Raida, Zbyněk (advisor)
Diplomová práce se zabývá metodou hybridních (hranových a uzlových) konečných prvků ve frekvenční i časové oblasti. Tato metoda je použita pro analýzu vlnovodu parallel-plate, v kterém jsou umístěny dvě dielektrické vrstvy. Jako ukončení vlnovodu je implementována dokonale přizpůsobená vrstva označována PML. Projekt řeší možný výběr PML vrstvy v časové oblasti. Metoda je programována v programu MATLAB a výsledky jsou porovnány s programem COMSOL Multiphysics.
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Modeling waveguides by time-domain finite elements
Fasora, Pavel ; Motl,, Milan (referee) ; Raida, Zbyněk (advisor)
The thesis deals with frequency domain finite elements and time domain finite elements. Derivation of the wave equation, generation of the discretization mesh and the composition of matrices for solving wave equation are presented. Exploitation of COMSOL Multiphysics for the analysis of the electromagnetic wave propagation in a wave guide is explained. Finally, in this thesis is described the m-file of MATLAB for analyzing electric field intensity of the waveguide in longitudinal direction to both domain. In last part is concisely exposed perfect match layers.
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Waveguide-SIW transitions
Bednarský, Vojtěch ; Láčík, Jaroslav (referee) ; Špůrek, Jan (advisor)
This work deals with the design of waveguide transitions. In this work I describe two usually used types of waveguides and that is classical rectangular waveguide with standardized designation WR-10, which is designed for working frequency 94GHz. The second type will be a waveguide integrated into the substrate called SIW. In the first part, numerical models of waveguides are calculated and transitions are created. Numerical models are simulated in CST Microwave Studio. Transitions are constructed in two types. Horizontal transition and orthogonal transition. The results of the first part are obtained dimensions of parameters from numerical models and S-parameters of transition sets.
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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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