National Repository of Grey Literature 53 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Antenna system for wireless microphones
Bartoš, Adam ; Lukeš, Zbyněk (referee) ; Láčík, Jaroslav (advisor)
Master's thesis deals with the design of an antenna system for wireless sound transmission used mainly in professional sound reinforcement. The introductory part deals generally with wireless microphones, frequency bands used and proven antenna types. Next, this work deals with signal distribution that is realized using the antenna splitter. The antenna parts is focused on easy production and real usage, therefore were selected antennas with appropriate properties suitable for small series production. This thesis includes simulation of each device, their real construction design and measurements of built prototypes and final products. All three produced devices – the rack splitter, /4 antenna and Helix antenna are fully working, achieve good parameters and are ready for further manufacturing and easy modifications in case of frequency band change requirement. The conclusion includes an overall assessment of the results achieved.
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.
Tunable loop antenna for ham radio
Šmerda, Jaroslav ; Šrámek, Petr (referee) ; Lukeš, Zbyněk (advisor)
This bachelor thesis is focused on the design and construction of loop antenna that can tune the stepper motor using capacitors. The antenna is designed for short waves used by radio amateurs. My task is to establish an antenna tuning using 4-position stepper motor controlled by a microprocessor, which will set the stepper motor to the positions that will change the capacity of capacitors needed to tune the antenna for the frequency band.
Measuring the velocity of projectiles by laser beam
Šmerda, Jaroslav ; Šebesta, Jiří (referee) ; Lukeš, Zbyněk (advisor)
Muzzle velocity is the speed of bullets, guns at the moment it leaves the barrel of a gun. Since this is a parameter related to the storyline, which takes place only shortly after the bullet leaves the barrel, this figure is the transition ballistics. The aim of this work is to design and construct a device for measuring the speed. Measurement consists in measuring the interval at which the bullet crosses the two laser beams. From this data, the performance will be calculated.
Power amplifier for shortwave radioamateur bands
Smutný, Štěpán ; Šebesta, Jiří (referee) ; Lukeš, Zbyněk (advisor)
The amplifier is designed in the class AB, for which is typical acceptable efficiency and relatively low quiescent power consumption. As active components, the MOSFETs transistors are used. Their quadratic transfer characteristic allows for a gain control by means of quiescent current setting. The principle of MOSFETs function will be described, along with their utilization in the class AB amplifier. Since the amplifier processes signals in the shortwave band, parasitic capacitances of the transistors reduces gain greatly. Therefore, these capacitances will have to be compensated by positive feedback. First, the function of the amplifier will be verified in PSPICE program, then design or selection of real components (including transformers, heat sink and bias control) will be carried out. By performing measurement on assembled amplifier, we have verified the gain control (doubling the quiescent current increases gain by 3dB). If the quiescent current is set to 1250mA, the gain exceeds 20dB in the range from 1.4MHz to 13.5MHz. Gain at high frequencies was achieved thanks to compensation by positive feedback.
L-band antenna and low noise amplifier
Kučera, Ondřej ; Lukeš, Zbyněk (referee) ; Záplata, Filip (advisor)
This master thesis is dealing with a system for receiving meteorological images from satellites placed on lower orbit. Furthermore it gives basic information about satellites NOAA, METOP and FY. It also includes derivations of equations, that define minimal requirements for receiving antenna and LNA. From reached parametres, energetic balance for connection of the satellite and Earth is calculated. The main part of the master thesis is designing of low-noise amplifier for L band. LNA is implemented on the substrate FR4 and Arlon DiClad 870, circuit is designed with elements of parametres, which are spread out or concentrated. The last part of the thesis describes design of antenna for reception of meteorological images.
RFID reader antenna
Trubák, Jan ; Lukeš, Zbyněk (referee) ; Mikulášek, Tomáš (advisor)
This thesis is focused on the design of the antenna to a specific application XY. Emphasis is placed on a narrow antenna beam width, which will ensure full-fledged profit for the tag directly below the antenna. This thesis presents a total of five proposals that could be used by XY application. This thesis also presents the results of field measurements, which confirm the improved characteristics of the antenna with parasitic patch.
Mini-whip antenna
Pařízek, Tomáš ; Lukeš, Zbyněk (referee) ; Raida, Zbyněk (advisor)
The thesis deals with the impedance matching of electrically very short antennas to the real resistance 50 . The antenna is considered as an input of an emitter follower, which plays the role of the impedance transformer. This follower transforms a large complex input impedance, which is typical for electrically short antennas, to a real output resistance. The output impedance was matched by appropriate matching circuitry to 50 in the frequency band of operation.
Design of analog control device for mini glasshouse
Řehák, Martin ; Lukeš, Zbyněk (referee) ; Petržela, Jiří (advisor)
Nowadays there are several options how to grow plants that do not come from our climatic belts are used to implement the greenhouses, where the artificially simulated environments, in which plants can vegetate. This work deals with the issue, plant growing in climates that are not for the plants of the rainforest, characteristic. It was necessary to create a greenhouse in which to guarantee the basic conditions for their growth. Such as humidity, temperature and lighting. He was taken into account at the design and implementation of the website.
Design of analog control device for mini glasshouse
Řehák, Martin ; Lukeš, Zbyněk (referee) ; Petržela, Jiří (advisor)
Nowadays there are several options how to grow plants that do not come from our climatic belts are used to implement the greenhouses, where the artificially simulated environments, in which plants can vegetate. This work deals with the issue, plant growing in climates that are not for the plants of the rainforest, characteristic. It was necessary to create a greenhouse in which to guarantee the basic conditions for their growth. Such as humidity, temperature and lighting. He was taken into account at the design and implementation of the website.

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