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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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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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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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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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Energy harvesting demonstrator
Kaděra, Petr ; Mikulášek, Tomáš (referee) ; Mrnka, Michal (advisor)
This semestral thesis is focused on radio frequency energy harvesting. The thesis describe parts of network that are essential for conversion of radio frequency energy into DC. It deals with various solutions to the given problem. The aim of the thesis is to design a proper antenna with supplemental circuits for commercial Powercast P2110B receiver which combines the function of a rectifier and a step-up DC/DC converter.
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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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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 Polarization for Indoor Antenna Measurement Range
Mrnka, M. ; Vélim, J.
The presented paper describes design of an original transmitting antenna for specific indoor far-field measurement range. The antenna is able to generate both senses of the circular polarization with high polarization purity by using stepped septum polarizer inside a waveguide. Very high suppression of the side lobes is achieved by utilization of the higher order modes in the aperture of the final horn antenna which is directly connected to the septum polarizer. The antenna was simulated and optimized in CST Microwave studio, measured and the data compared. Excellent agreement between simulation and experiment was achieved.
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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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Study of gel electrolytes properties by MR methods
Kořínek, R. ; Vondrák, Jiří ; Bartušek, Karel ; Mrnka, M.
In this paper are introduced basic methods for measuring the properties of the gel structure during polymerization, particularly relaxation times T1, T2 spin density and diffusion coefficients. We can obtain these parameters using the MR pulse sequences. To measure of relaxation time T1 are used SR techniques (Saturation Recovery) and IR techniques (Inversion Recovery) usually. To measure of relaxation time T2 can be used SE (Spin Echo) technique. To measure diffusion coefficinets are used PFG-SE and PFG-SSE methods (Pulsed Field Gradient Spin Echo a Pulsed Field Gradient Stimulated Echo) and of course their modification. Experiment itself is described sample preparation of gel electrolytes and to measure their relaxation times.
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