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Modeling antennas of the VUT 100 aircraft
Starý, Vladimír ; Tobola,, Pavel (referee) ; Raida, Zbyněk (advisor)
The thesis is aimed to analyze parameters of antennas, and work out the computer, which can be used to the modeling of the radiation of antennas of the VUT 100 aircraft. First, used antennas are divided according to the operation frequencies, and the polarization. Second, a MATLAB program is developed and described. The program computes radiation patterns at different frequencies for the different location of antennas on the VUT aircraft. Finally, the MATLAB optimization program is develop and described. The program changes the position of antennas so that the requirements of aircraft producer can be met.
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Synthesis of electromagnetic bandgap structures
Šedý, Michal ; Kovács, Peter (referee) ; Raida, Zbyněk (advisor)
In microwave frequency band, the planar technology is mainly used to fabricate electronic circuits. Propagation of surface waves belongs to the significant problem of this technology. Surface waves can cause unwanted coupling among particular parts of the structure and can degrade its parameters. The problem can be solved using an electromagnetic band gap structure (EBG). These periodic structures are able to suppress surface waves in different frequency bands. This thesis is focused on the modeling of these structures in the program COMSOL Multiphysics.
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Synthesis of microwave resonators
Šeděnka, Vladimír ; Dědková, Jarmila (referee) ; Raida, Zbyněk (advisor)
The thesis deals with microwave resonators synthesis in Matlab environment. Due to the multi-objective optimization, the shape of the resonátor is subsequently changed to fit requested frequency properties. Particle swarm optimization and frequency domain finite element method are used. Accuracy of the different number of elements was tested. Values of several optimization parameters were balanced to reach the maximal efficiency of the optimization.
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Neural networks for EMC modeling of small airplanes
Koudelka, Vlastimil ; Goňa,, Stanislav (referee) ; Raida, Zbyněk (advisor)
This thesis deals with neural modeling of electromagnetic field inside small aircrafts, witch can contain composite materials in their construction. Introduction to neural networks and its application in EMC of small airplanes is discussed in the first part of the text. In the second part of this thesis we design a simple EM model of small airplane. The airplane is simulated by two parallel dielectric layers (the left-hand side wall and the right hand side wall of the airplane). The layers are put into a rectangular metallic waveguide terminated by the absorber in order to simulate the illumination of the airplane by the external wave (both of the harmonic nature and pulse one). Numerical analyses are performed to search the relations between the distribution of an electromagnetic field inside the aircraft and electric parameters of model walls. The results of numerical analyses are used to train two types of neural network. In this way we can obtain accurate continuous model of electromagnetic field inside the aircraft. For the comparison with neural networks a multi-dimensional cubic spline interpolation is provided also. Neural classifiers are also investigated. We use them for classification of imaginary composite materials in terms of EMC. The nearest neighbour algorithm is applied as a classic approach to problem of classification.
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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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Improving antenna parameters by the application of metamaterials
Šporik, Vladimír ; Hertl, Ivo (referee) ; Raida, Zbyněk (advisor)
The thesis is focused on the design of a planar resonant-type antenna, which exploits a proper combination of left- and right-handed properties of transmission lines. This transmission line is called CRLH TL and is based on Sievenpiper mushroom structure. Advantages of the proposed antenna concept are demonstrated by a detailed comparison of its basic properties with the properties of a conventional patch antenna.
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Modeling metamaterial microwave resonators
Zvolenský, Tomáš ; Kovács, Peter (referee) ; Raida, Zbyněk (advisor)
Práce je věnována modelování mikrovlnných rezonátorů z metamateriálů (materiálů se záporným indexem lomu). V úvodu je rozebráno, co metamateriály jsou, jak se vytvářejí a které jejich vlastnosti jsou podstatné při návrhu rezonátorů. Následuje návrh planárního rezonátoru z metamateriálů. Pro tento účel byly naprogramovány funkce počítající rozměry jednotlivých součástí struktury. Simulace navržené struktury probíhala v programu Zeland IE3D. Simulované struktury byly optimalizovány s ohledem na požadované kmitočty rezonance. První rezonátor sestával z jedné elementární buňky, druhý ze dvou buněk, naladěných na rozdílné kmitočty. Rezonátory byly vyrobeny a experimentálně byly ověřeny jejich vlastnosti.
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Modeling frequency selective surfaces in COMSOL Multiphysics
Höhn, Tomáš ; Oliva, Lukáš (referee) ; Raida, Zbyněk (advisor)
Metoda konečných prvků implementovaná v programu COMSOL Multiphysics je využívána k analýze tzv. free-standing kmitočtově selektivních povrchů ve 3D. Tyto modely jsou následně doplněny o periodické okrajové podmínky. Dále jsou free-standing povrchy doplněny o vrstvy dielektrika a je zkoumán jejich vliv na modul činitele odrazu. V analytické části jsou vyhodnoceny vlivy počtu elementů diskretizační mřížky na přesnost výsledku a délku výpočtů. Výsledky jsou srovnávány vzhledem k výsledkům uvedeným v literatuře [5]. V závěrečné části práce je vysvětlen postup při generování m-file pro obdélníkový element a použití globálního optimalizačního algoritmu PSO, který automaticky upravuje rozměry vodivého motivu tak, aby bylo dosaženo průběhu modulu činitele odrazu podle požadovaného průběhu.
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Computing directivity patterns in Comsol Multiphysics
Ryšánek, Martin ; Lukeš, Zbyněk (referee) ; Raida, Zbyněk (advisor)
The individual project – Computing directivity patterns in Comsol Multiphysics. In the first part, the theoretical background for monopole antennas is reviewed. The second part is focused on the analysis of several types of monopoles in COMSOL Multiphysics, and on the calculation of their radiation patterns and impedances. Finally, simulation results are presented and discussed.
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