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Antennas with metamaterial radomes
Martínek, Luděk ; Tkadlec, Roman (referee) ; Pítra, Kamil (advisor)
This thesis deals with microstrip antennas covered by the metamaterials. First, are described planar antennas, their problems and the emergence of surface waves. 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. It is shown how the EBG structure in the function superstate improve directivity and antenna gain. Radiation conventional microstrip antenna with metallo-dielectric EBG superstrate and with the purely dielectric double-layer superstrate is described. The both structures are designed and simulated in CST Microwave Studio program. Further is described the antenna radiation with so-called mushroom structure and metallo-dielectric EBG superstate. The structure is again designed and simulated in CST MWS program. Finally, there are two structures with metallo-dielectric superstate implemented and measured.
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Design of diplexer based on coaxial resonators
Štěpánek, Michal ; Tkadlec, Roman (referee) ; Wolanský, David (advisor)
This thesis deals with the analysis of coaxial cavity filters and synthesis of generic topology of these filters. Transfer function comes out the synthesis, which is based on low-pass prototype and similarity with real structure. The next aim of this thesis is to build the basic software for coaxial cavity filters synthesis from engaged characteristic parameters of the filter. This work also includes the analysis of coupling matrix synthesis based on transfer function, where we can use direct coupling or cross-coupling between resonators. The last point is focused on the diplexer filter based on specified parameters and obtained coupling matrix. Entire diplexer model is optimized using Tuning-Space Mapping method.
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Dual-Band Helix Antenna for WiFi band
Šrajbr, Michal ; Tkadlec, Roman (referee) ; Pítra, Kamil (advisor)
This master’s thesis is focused on the properties and types of helical antennas. The helical antenna work in the different modes. These modes are described in this thesis. There are also discussed possibility for design a dual-band helical antennas. The main aim of this work is the selection of a suitable solution and design a dual-band helical antenna for the WiFi band working at resonance frequencies of 2,4 GHz and 5 GHz. The simulation of this antenna was performed in the program CST Microwave studio.
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Wideband planar antennas
Špatenka, Vojtěch ; Tkadlec, Roman (referee) ; Wolanský, David (advisor)
In this master´s thesis an issue of broadband planar antennas was analyzed. Firstly, the basic elements that affect bandwidth, such as the influence of the dieletric substrate, suitable shape or feeding network, were described. Furthermore technics that can be used to widen the band of the planar antennas were described. These technics were applied to a chosen type of a planar antenna. This antenna was modeled and simulated for desired dielectric substrate in CST STUDIO SUITE 2010 software. Feeding network with power dividers was designed for the antenna array. In order to obtain a higher gain, the antenna was implemented into the 2x2 element array. The results of the simulation are evaluated in the conclusion.
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Wideband Sinuous Antenna with Dual Polarization
Haloda, Jiří ; Tkadlec, Roman (referee) ; Pítra, Kamil (advisor)
This paper deals with sinuous broadband antenna, witch operating frequency 1 to 6 GHz. The antenna parameters, which change their physical dimension were shown in this paper. Antenna structure is planar and feeding network line have to be planar too. There are different ways to describe and construct from unbalanced to balanced line by baluns. There are also design impedance transform to match antenna in this paper. The simulation and measured results are showen the antenna has wideband character.
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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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Measurement of the near field distribution
Macháček, Ivan ; Tkadlec, Roman (referee) ; Nováček, Zdeněk (advisor)
The aim of this work was to prepare measuring workplace, perform the verication measurement, including the measurement phase, on the cylindrical surface. Measured data were compared with theoretical assumptions and were calculated directional patterns. Probes for measurement in the near sield were designed and realized.
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Optimizing coaxial filters by Tuning-Space Mapping in CST
Wolanský, David ; Tkadlec, Roman (referee) ; Raida, Zbyněk (advisor)
This thesis deals with optimization of coaxial cavity filters. It thoroughly describes optimization method Tuning – Space Mapping (TSM) in CST Studio. It focuses on the explanation of the fine and the coarse model and their mutual link. The whole algorithm is illustrated and tested on the third-order coaxial cavity filter working in the band of 880 – 960MHz. In order to check the function of TSM, the algorithm is applied on fourth-order filter, triplet filter and quadruplet filter. Another part of the thesis focuses on the automatization of the whole optimization procedure. Macros for automatic determination of calibration constants and automatic calibration process between the coarse and the fine model are proposed and programmed in CST. The complete optimization procedure is applied on optimization of seventh-order filter with two cross couplings.
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Near field of the dipole antennas
Beran, Vlastimil ; Tkadlec, Roman (referee) ; Nováček, Zdeněk (advisor)
The thesis describes the radiation of dipole antennas in near field area. More methods for evaluation of spatial dipole field arrangement are compared. The work target for practical use is to create software for simulation of near field values placed in planar or cylindrical observation plane. The computer programme is applicable to single dipole or dipole array. The limits for human body exposition of non-ionizing radiation are here implemented for compliance purpose in hygienic evaluations. The simulated results of field distribution are possible to display as graphs or save to data file. The results of own calculation are compared with results obtained by some commercial software as well by measurement of field components under model conditions.
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