|
|
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.
|
|
|
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).
|
|
|
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).
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
Laboratory current source with direct digital synthesis
Pěčonka, David ; Hejtmánek, Tomáš (referee) ; Mikulka, Jan (advisor)
The work deals with the design of a laboratory generator with a current output for supplying elements with a maximum impedance in units of k. The text itself discusses the designs of individual parts of the device and the choice of suitable components for their implementation. The sub-chapters deal with the design process of the power supply and digital parts are followed by the mechanical construction of the source, which ends with the verification of the expected properties of the designed and constructed source. The result of the work is a source with a current output of up to ±10 mA with the possibility of parameterization of the frequency, amplitude and shape of the signal using control elements and also digitally using the universal serial bus. The signal is generated using a direct digital synthesis (DDS) system. The generator itself is supplied by a rechargeable battery.
|
|
|
Communication infrastructure for drone swarm
Kubant, Michal ; Mikulka, Jan (referee) ; Janoušek, Jiří (advisor)
This thesis deals with creation and testing of wireless communication network used for transmission of multimedia and telemetry data in swarm of unmanned aerial vehicles. In the first part of this work are presented functions of the IEEE 802.11ax and their possible usage. The second part if thesis describes configuration of network elements in the wireless network, and discusses maximum transmission speed. The third part presents testing of the assembled network, designs and use of protocols for multimedia streams in a swarm of drones. Also the results are briefly evaluated and illustrated. The fourth part analyzes the methodology of testing the network in the outdoor environment, it discusses the results obtained by using this methodology in different outdoor spaces, and further proposes suitable solutions for improving the efficiency and range of the wireless network.
|
|
|
Optimizing Image Reconstruction in Electrical Impedance Tomography
Dušek, Jan ; Brančík, Lubomír (referee) ; Sikora, inž Jan (referee) ; Mikulka, Jan (advisor)
Tato disertační práce pojednává o optimalizaci algoritmů pro rekonstrukci obrazu neznámé měrné vodivosti z měřených dat pořízených elektrickou impedanční tomografií. Danou problematiku zde věcně vymezuje několik různých prvků, zejména pak stručný matematický popis dopředné a inverzní úlohy řešené různými přístupy, metodika měření a pořizování dat pro rekonstrukci a přehled dostupných numerických nástrojů. Uvedenou charakteristiku rozšiřuje rozbor optimalizací parametrů modelu ovlivňujících přesnost rekonstrukce, způsoby paralelního zpracování algoritmů a souhrn dostupných zařízení pro měření tomografických dat. Na základě získaných poznatků byla navržena optimalizace parametrů matematického modelu, která umožňuje jeho velmi přesný návrh dle měřených dat. V této souvislosti dochází ke snížení nejistoty rekonstrukce rozložení konduktivity. Pro zefektivnění procesu získávání dat bylo navrženo zařízení k automatizaci tomografie s důrazem na cenovou dostupnost a snížení nejistoty měření. V oblasti tvorby numerického modelu byly dále zkoumány možnosti užití otevřených a uzavřených domén pro různé metody regularizace a hrubost sítě, a to s ohledem na velikost chyby rekonstruované konduktivity a výpočetní náročnost. Součástí práce je také paralelizace subalgoritmů rekonstrukce s využitím vícejádrové grafické karty. Předložené výsledky mají přímý vliv na snížení nejistoty rekonstrukce (optimalizací počáteční hodnoty konduktivity, rozmístění elektrod a tvarové deformace domény, regularizačních metod a typu domén) a urychlení výpočtů paralelizací algoritmů, přičemž výzkum byl podpořen vlastním návrhem jednotky pro automatizaci tomografie.
|
|
|
Virtual measuring instruments to support the education
Bilík, Petr ; Marcoň, Petr (referee) ; Mikulka, Jan (advisor)
This diploma thesis deals with the creation of the Virtual Measuring Instruments web application. This tool mainly enables us to simulate the real measuring instruments widely used in the laboratories of FEEC BUT. It is intended to serve students for initial acquaintance with specific devices. The theoretical part is focused on the research into the web applications programming and suitable programming languages to implement the proposed application are selected. Furthermore, the specific virtualized devices are described. The result of the experimental part consists in creating a universal application interface to extend the proposed application with other devices. Finally, the specific tests of the developed platform are presented.
|
guest ::
