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Wireless doorbell with digital voice transmission
Partsch, Patrik ; Šebesta, Jiří (referee) ; Mikulka, Jan (advisor)
The master´s thesis deals with a design and layout of wireless doorbell with digital voice transmission. It also includes the nRF9E5 circuit analysis. In the beginning of the document there is characterization of the problem in general. Next part describes a layout example for the application schematic, a layout of printed circuit board and a layout of software. nRF9E5 is a true single chip system with fully integrated RF transceiver, 8051 compatible microcontroller and a four input 10 bit AD converter. Despite of all studies of available literature I have found only very little particular information related to this matter. In general, the main aim of this work is to make the wireless doorbell with digital voice transmission. Further, ilustrated schematics are enclosed as a attachement of this thesis.
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Methods for evaluation of quality of automotive filters
Sedlák, Jiří ; Drexler, Petr (referee) ; Mikulka, Jan (advisor)
This bachelor thesis deals with theoretical research, description and design of three individual methods of defective air filters detection. Individual methods are described and compared in terms of their technical difficulty and expected efficiency. These methods are optical test, acoustic test, pressure test and the method of detection of gas CO2. All researched methods were proved practically and the measurements of detection of defective air filters were taken. The defect of air filter was detected by use of optical test.
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Operating parameters of LED light sources
Janík, Daniel ; Mikulka, Jan (referee) ; Havlíková, Marie (advisor)
The aim of the thesis is to introduce the basic photometric quantities and operating parameters of LED light sources, according to which the light sources are evaluated and compared. The thesis examines effects of high temperature and elevated stress on LED retrofits and a design of measurement methods to measure these influences. According to the proposed methods, nine samples of light sources were measured and compared to each other on a basis of the measurements. Comparison was made from the point of view of the energy as well as the quality of the produced light. The results were also compared to the parameters specified by the producers.
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Laser source with fiber-optic output
Roupec, Tomáš ; Mikulka, Jan (referee) ; Drexler, Petr (advisor)
This term project deals with the semiconductor laser components, and how it works. Additionally, there is an optical fiber ant networking with laser. It is written of power and cooling laser diodes and such information suggested the possible involvement of the laser diode. At the end of this work is designed laser´s exciter with charging and adjacent circuits.
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WLAN and Bluetooth Systems Coexistence
Mikulka, Jan ; Hanus, Stanislav (advisor)
The dissertation thesis deals with a WLAN and Bluetooth systems coexistence. A Bluetooth standard works in an unlicensed frequency band 2,402 – 2,480 GHz. This frequency band is also used by an IEEE 802.11b/g standard (Wi-Fi) which is the most extended representative of WLAN networks. Because Bluetooth and Wi-Fi systems operate in the same frequency band, a mutual signal degradation may appear, when devices are collocated in the same area. In the first part of the dissertation thesis there is a brief summary of 2,402 - 2,480 GHz frequency band regulations and its usage. There are described physical layers of Bluetooth and IEEE 802.11b/g standards and techniques used for a collision avoidance. The main part of the dissertation thesis deals with a development of a new Matlab Simulink model for investigations of the Bluetooth and Wi-Fi standards coexistence. Physical layer models and results of the coexistence simulations are verified by a measurement in real conditions with a help of a modern vector signal analyzer. The results are presented in a graphical form and a brief summary is attached at the end of each chapter. Corresponding tables of simulated and measured values are available in the enclosed CD.
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Design of magnetic bar-code read head
Kadlčík, Libor ; Drexler, Petr (referee) ; Mikulka, Jan (advisor)
Magnetic bar-code is composed from ferromagnetic bars printed on a substrate. The amount of ferromagnetic material is low, therefore reading magnetic barcode requires sensitive methods. Principle of methods of sensing both low-intensity magnetic field (fluxgates) and detecting low concentration of ferromagnetic material (resonant circuit, differential sensor) will be described. There are sensors producing frequency-modulated signal, therefore we focus on frequency demodulators as well. Signal acquired by sensor suffers from convolution distortion, reconstruction methods will be introduced. The assembled device consists of sensing oscillator, frequency demodulator, amplifier and reconstructing circuit. Frequency demodulation is done by phase-locked loop or differential demodulator. Reconstruction is based on detection of inflection points, producing square signal (representing bars of barcode). Design of these blocks is described. The device is able to read magnetic barcodes and reconstruct convolutionary distorted acquired signal. The differential demodulator exhibits low noise and low temperature drift (contrary to phase-locked loop). Signal produced by reading 2 mm wide bars is reconstructed without any problems, bars of width less than 1 mm cause troubles in certain cases (due to high degree of convolution distortion).
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Flash OFDM network efficiency
Jireček, Martin ; Mikulka, Jan (referee) ; Hanus, Stanislav (advisor)
The FLASH-OFDM networks (Fast Low-latency Access with Seamless Handoff-Orthogonal Frequency-Division Multiplexing) are insert to network of fourth generations. The system are set to fast data transfer. These networks have lower latency than network of third generations. On average is transmission speed for downlink cca 1,5Mb/s and for uplink cca 300-500kb/s. In connection with progress of high-speed network and systems with finite mobility (Bluetooth, IEEE 802.11), creationed want of new standard, which connect both merits. For WiMAX was defined new basic requirements: • mobility of user, • high-speed data transfer with roaming, • the lest latency of systém using aplications in real time, • high count of at the same time communication users in cell, • chance of better control QoS (Quality of Service).
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Study of substances transport in plants stalks
Doubek, Vladimír ; Kubásek, Radek (referee) ; Mikulka, Jan (advisor)
This thesis deals procedure nuclear magnetic resonance and next three of basic measuring technics NMR. Magnetic resonance exploit, that anyone proton and neutron have dynamics moment. Is based on monitoring response coring situated to magnetic field B0 and on interaction with HF electromagnetical wave. Measuring of response signal differ in feed RF pulse. Method spin echo (SE) is based on two pulses 90° and 180° in contrast by Inverse recovery (IR), where is it conversely.By method Hahn echo (measuring efficient relaxation time T2*) is brought 90° pulse. For all methods is final signal over stopping process captured in receiving inductor.
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Analog-digital module for electrical impedance tomography
Zimniok, David ; Mikulka, Jan
The present text introduces the concept of data collecting (voltages and currents) from a phantom connected to electrical impedance tomography. The concept involves a method for signal multiplexing from up to 256 electrodes and the current source for such probes. Considering the high number of electrodes and the estimated extended distances between the probes and the measuring card, the method recommends using probes to convert the measured voltage to a current loop, making them suitable for measuring small voltage levels in the millivolt range.
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Analog-digital module for electrical impedance tomography
Zimniok, David ; Hejtmánek, Tomáš (referee) ; Mikulka, Jan (advisor)
Tato bakalářská práce se zabývá elektrickou impedanční tomografií a jejími problémy. Prvním problémem je měření napětí v širokém rozsahu od milivoltů po desítky voltů. Druhým problémem je měření fáze impedance pomocí mikroprocesoru bez lidské pomoci. Také bylo třeba vyřešit problém s návrhem elektrod a s přenosem malého napětí na velké vzdálenosti mezi měřeným objektem a navrženým zařízením pro zpracování signálů. Ke zpracování signálů a komunikaci byl zvolen mikroprocesor ARM doplněný o zesilovač, který má nastavitelné zesílení a také lineární optočlen pro ochranu mikroprocesoru. Pro zajištění přenosu měřeného napětí na velké vzdálenosti bez ztráty dat je navržena aktivní sonda. Data jsou přenášena prostřednictvím proudové smyčky.
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