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Study of gel electrolytes properties by MR methods
Mrnka, Michal ; Gescheidtová, Eva (referee) ; Bartušek, Karel (advisor)
Theoretical part of the work deals with explanation of nuclear magnetic resonance phenomenon, relaxation processes in system of nuclear spins, basic techniques for measurement of relaxation times. There are described diffusion and techniques for diffusion coefficient measurement including method for suppressing the background gradient. Experimental part describes preparation of gel electrolytes samples and measurement of relaxation times. Sodium salt was used as a conductive agent. There is interpreted dependence of relaxation times on polymerization times and on concentration of conductive agent in gels.
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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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Radiation efficiency measurements of dielectric resonator antennas using Wheeler method
Sedler, David ; Mikulášek, Tomáš (referee) ; Mrnka, Michal (advisor)
Bachelor thesis discusses the dielectric resonators as antenna elements. This work includes description field rectangular resonators, possible dielectric materials, shapes and feeds, e.g. coaxial probe, microstrip line or substrate integrated waveguide. In project is listed measuring radiation efficiency of antennas in general and method used wheeler cavity. Bachelor thesis contains design of waveguide with proposal of dielectric resonator. Design of the antenna was conducted in software CST Microwave Studio and there are demonstrated results of simulations. Radiation efficiency of the dielectric resonator antenna was measured by the Wheeler method and the efficiency received from the measured gain. The work included the measured results together with a comparison of the measurements of both methods and simulations.
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Vibrational energy harvesting demonstrator
Uhliar, Marek ; Götthans, Tomáš (referee) ; Mrnka, Michal (advisor)
The aim of the thesis is to solve the problem of energy collection from vibrations, transformation into electric energy, which can be suitably used by the end device. In the next section, the reader is acquainted with possible circuits that can be used to process the collected electrical energy. The last part of the thesis deals with the design of the auxiliary circuits for energy collection and with the design of the demonstration device, which will use the converted energy to measure the air temperature and humidity. The measured values will then be displayed on the LCD.
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Antena integrated to automobile seat
Gulda, Tomáš ; Mrnka, Michal (referee) ; Cupal, Miroslav (advisor)
This thesis is focused on the design of the antenna integrated to automobile seat. Thesis explains the basics of RFID technology, and how RFID works. Especially explains the design of tag, which works in the UHF band. The tag was designed in the CST Microwave studio, where simulations were realized to verify basic properties of the tag such as S11 parameter and directivity. The thesis also contains simulation of the impact of automobile seat on the directivity. Here is the description of how the antenna was made on a textile substrate and here are also measured properties of the antenna.
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Heart rate measurement using pulse oximetry on unconventional parts of the human body
Varmužová, Zdeňka ; Mrnka, Michal (referee) ; Cupal, Miroslav (advisor)
This study deals with the method of measuring heart rate using pulse oximetry. It describes the basic principles of this method for determining both heart rate and blood oxygenation. It examines the possibilities of placing the sensor on non-standard places of the human body. It also discusses the possible shortcomings of the method as well as the inaccuracies of measurements in certain places on the body and the possibilities of mounting the sensor and the use of the product in ordinary life. Later it presents the design for the heart rate measuring device used on the selected body part, that is forehead, and compares it with commercialy available products.
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Perforated Dielectrics and Higher-Order Mode Dielectric Resonator Antennas
Mrnka, Michal ; Bonefačić, Davor (referee) ; Mrozowski, Michal (referee) ; Raida, Zbyněk (advisor)
Práce se zabývá buzením vyšších módů v kvádrových a válcových dielektrických rezonátorových anténách pro účely zvýšení zisku. Pomocí numerických simulací jsou studovány vlastnosti a limity anténních prvků. Je zkoumáná vzájemní vazba mezi dielektrickými rezonátorovými anténami pracujícími s vyššími vidy a na základě výsledků je možno usuzovat o vhodnosti těchto prvků k popužití v anténních řadách. V práci je popsán analytický model efektivní permitivity perforovaných dielektrik, který respektuje anizotropní povahu tohoto materiálu. Model je založen na Maxwell Garnettové aproximácií nehomogenních materiálů. Dále jsou studovány povrchové vlny na perforovaných substrátech a je ověřena použitelnost teoretického modelu i v tomto případě. Nakonec jsou studovány dielektrické rezonátorové antény vytvořené pomocí perforací v dielektrickém substrátu a je demonstrováno zhoršení určitých vlastností takových antén.
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Circularly polarized dielectric resonator antenna
Zechmeister, Jaroslav ; Kufa, Martin (referee) ; Mrnka, Michal (advisor)
This thesis discusses the design circularly polarized dielectric resonator antennas for ISM band 5,8 GHz. In this work are explained and compared different ways of resonator feeding. There are also discussed the possibility of generating a circular polarization from a aperture feeding. Two methods of generating circular polarization in dielectric resonator antennas are simulated in CST Microwave Studio. This methods are C-shaped slot and cross slot. For antenna with cross slot feeding is also simulated effect of the manufacturing process to characteristics proposed antenna. The antenna is made, measured and the results are compared with simulations.
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Wireless power transfer by inductive coupling for biomedical applications
Studený, Jakub ; Dřínovský, Jiří (referee) ; Mrnka, Michal (advisor)
The bachelor thesis deals with wireless power transfer implemented using a couple of inductively coupled planar coils. A procedure for designing planar coils using the Wheeler method is described as well as the process of simulating wireless transmission in a 3D electromagnetic field simulator. The conclusion of the thesis is devoted to the implementation of the designed coils with adaptive circuits, measurement of transmission by vector analyzer, investigation into the impact of coil distance, and mutual rotation of the coils and the materials interposed the between coils.
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Substrate integrated dielectric resonator antenna
Jedlička, Lukáš ; Horák, Jiří (referee) ; Mrnka, Michal (advisor)
The bachelor´s thesis deals with the design of the dielectric resonator antenna in the microwave band X, where the resonator is made by air perforations. The antenna is made by two layers. The antenna is supplied by the substrate integrated waveguide. The design of the dimensions to achieve the desired resonance frequency of the dielectric resonator and integration of resonator is described. The whole antenna is designed in the CST Microwave Studio software.
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