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MW Converter for SW Receiver
Lejsková, Alena ; Lukeš, Zbyněk (referee) ; Šebesta, Jiří (advisor)
This thesis concerns about the network synthesis of receivers with the demand for conversion of the input signal and a following implementation of assigned converter. At first it introduces the readers with the basic division of radio waves and with parts, which are important for a high-quality receiver, then it deals with general properties of input networks of receivers, division of parts and kinds of connection, that are used in the communications. The concept of connection is intended to nonspecialists too, that is why it describes step by step each of parts of the network, including the calculation or possible solution and the choice of convenient parts. The aim is also to present the frequency conversion as an important part of signal receiving that we want to use in communication systems.
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Autonomous outdoor system for growing plants
Schmidt, Dominik ; Lukeš, Zbyněk (referee) ; Petržela, Jiří (advisor)
This diploma thesis deals with maintaining possibilities for appropriate climatic conditions in outdoor greenhouse. The importance for growing plants is an appropriate temperature, humidity and adequate supply of water. The aim of the study is to suggest an apparatus sustaining beforehand defined conditions in the greenhouse with minimal requirements for maintenance. Apparatus uses analogue control by applying photosezistor and thermistor. For power supply are DC-DC converters used.
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Automatic Antenna Tuner
Šváb, Jaroslav ; Lukeš, Zbyněk (referee) ; Šebesta, Jiří (advisor)
This degree work deals with the design and implementation of an automatic antenna tuner for short-wave transmitters. The device works within the short-wave range in (1.5 MHz - 30 MHz) band according to the selection of the given frequency. Its principle is that the tuner has a small range of adapted impedances, but it is usually sufficient for fine tuning of most deviations in the system of antenna 50 - feeder 50 - transceiver outlet 50 . It is also equipped with memories which the settings for the individual bands or frequency segments are stored into. Then the transition from one band to another is quick, easy and, first of all, safe, which is a great advantage. In automatic mode, a SWR limit from which the tuner should start to tune can be set. Interconnection with a TRX is not necessary in a fully automatic mode, the device tunes automatically after keying if the set limit of SWR has been exceeded. The automatic tuning is very quick with this device, if the antenna being tuned is not stored in the memory the tuning lasts ca 0.5 - 6 s, if the tuner uses the memory. It could be said that the work with the tuner is without problems, it is possible to learn to control it in a short time. The tuner is small and light. The result of the whole project is a compact device controlled by the user by means of push buttons.
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Optimization of multiband antennas using MATLAB environment
Žabokrtský, Michal ; Lukeš, Zbyněk (referee) ; Oliva, Lukáš (advisor)
The theme of this Bachelor thesis is the optimalization with the help of global methods and their implementation in MATLAB. Firstly, the theory of planar antennae, the ways of their use and the power supply options are analysed. As the next item, the general theory of optimalization is described. Firstly, the theories of local and global optimalization methods are mentioned. The method of Particle Swarm Optimization was chosen from the global optimalization methods. Its theory is explained and the way of applying it to optimalization of the planar antenna is mentioned. In the following part, the implementation of PSO algorithm to MATLAB environment and the usage of this method, programmed to optimalize a provided model of planar antenna in COMSOL Multiphysics, are described. The model was succesfully optimalized to required frequences (1,8 GHz and 2,4 GHz). The results of the optimalization are presented in this part, too – changes of frequency in iteration, changes of the particular measures in iterations. As the following step, the verification of the acquired results was performed in CST Microwave Studio. After considering the differences of results between COMSOL Multiphysics a CST Microwave Studio, an adjustment of the antenna to the required frequency had to be made. At the end, the results of the adjusted antenna are presented (development of return loss of antenna S11, radiating pattern and current distribution in the antenna).
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Design of reflector antenna for special radar applications
Kačmařík, Ivo ; Oliva, Lukáš (referee) ; Lukeš, Zbyněk (advisor)
The aim of this bachelor’s thesis was to design small parabolic reflector antenna in program CST Microwave Studio and it’s execution and verifying of it’s parameters by the laboratory measurements. Basic demands were rational proportions of the antenna and it’s good electrical properties, especially optimization of impedance matching and directional characteristics.
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Planar antenna arrays for RFID applications
Pochobradský, Jakub ; Horák, David (referee) ; Lukeš, Zbyněk (advisor)
This thesis describes the basic principles of radio frequency identification, basic characteristics of patch antennas, the possibility of their feeding and design of planar antenna series. Are discussed, impedance matching options. The selected antenna arrays were realised, measuring their parameters was down and measured parameters was compared with simulation results.
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Antenna for receiving of DVB-T signal
Šmarda, Marek ; Lukeš, Zbyněk (referee) ; Pokorný, Michal (advisor)
The content of this work is to study selected antenna systems suitable for receiving of DVB – T. The various antenna systems will be simulated in the program for the simulation of electromagnetic field (e.g, CST Studio) and the simulation results will be commented (e.g. graphs and diagrams of radiation). Selected antenna system will be made and experimentally measured.
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Automatic antenna analyser
Dufek, Ivo ; Šebesta, Jan (referee) ; Lukeš, Zbyněk (advisor)
This project is dealing with methods of measuring impedances of the antenna systems in the frequency range from the low frequencies to the very high frequencies. There is a discussion about different methods of measuring impedance and each technique is critically evaluated. In terms of this project is compared few types of the professional antenna analyzers. According to this comparison there was made the concept of my own antenna analyzer. There is a detailed description of the design of this device’s important parts including software equipment. Designed instrument has been built and tested.
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