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Controllable Frequency Filters with Modern Active Elements
Preclík, Milan ; Jeřábek, Jan (referee) ; Koton, Jaroslav (advisor)
The work deals with design of transformation cells suitable for realization of higher orders frequency filters with possibility of cutoff frequency control. At first, there is a common description of frequency filters and active elements like current and voltage conveyors. Furthermore assumptions of cutoff frequency control are defined which result in a convenient characteristical equation. Phylosophy of synthetic elements DP , EP , DS , ES including a possibility of change of cutoff frequency is next in line. By exploitation of synthetic elements theory new circuit’s schemes of transformation cells are searched. The work continues with the choice of appropriate transformation cells for resulting circuit’s solutions of frequency filters with possibility of cutoff frequency control by using transfer coefficients of active elements or with help of passive elements. The work concludes with verification of its proper function based on a simulation executed in OrCAD and with practical implementation of choosen circuit’s solution.
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Voltage Conveyors in Linear Blocks
Dohnal, Pavel ; Jeřábek, Jan (referee) ; Koton, Jaroslav (advisor)
The main goal of this diploma thesis will be realization of tunable frequency filters using voltage conveyors, that are only little explored yet. At the beginnig of diploma thesis the frequency filters and their types will be defined. The theory of voltage conveyors based on principle of duality results from the character of current conveyors. Accordingly these active components will be closely presented. At first there will be defined individual types of voltage conveyors and their closer characteristics. Then design methods of frequency filters using unconventional active components will be described. There will be defined the method of the total admitance net, subsequently design using synthetic components and at the end there will be presented method using follow graphs that will be used to design concrete circuit solution. Using follow graphs method will be found circuit solutions of current structures with unconventional active components. During searching circuit solutions will be very important the posibility to operate the quality factor. That can be obtained by two ways. One way is the activ operation which is done by coeficients of the activ component. Other way is operating using the passiv component. There are found 26 circuits that realize condition of active operating using two active and four passive components. One of these circuits will be chosen and simulated in simulation program PSpice. To compare both methods of operation there will be compiled some circuit with passive operating with two active and five passive components and one of the passive components will be able to operate the quality factor. This circuit will be simulated in the simulation program PSpice again. The circuit will be real compiled and experimentaly measured in laboratory. Results of this measurement will be compared with calculated values and with values acquired from the simulations.
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MPKT communication protocol extension on .NET platform
Görlich, Tomáš ; Malý, Jan (referee) ; Jeřábek, Jan (advisor)
This thesis is focused on extension of MPKT 2008 communication protocol. It has been made analysis of this protocol version and proposals to improve and extend this version with other options have been raised. It has been created a new version of the protocol on the basis of the proposals. Then the .NET platform has been presented and its architecture has been described. The C# language available on the .NET platform has been chosen to implement the new protocol version and its facilities for network communication and threading have been described. It has been said an assessment of the application of this programming language in practical lessons. A proposal to update tutorial texts has been made.
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Analysis of the wireless network security
Bencel, Jozef ; Koutný, Martin (referee) ; Jeřábek, Jan (advisor)
This master's thesis deals with security of wireless network standard 802.11. There are described security mechanisms as hide SSID, MAC address filtering, WEP, WPA, WPA2 protocols. There are described also the most often kinds of attacks (Denial of Service, disclosure WEP key, Man-in-the-Middle). The work contains investigation of used security mechanisms in wireless networks in parts of Brno. There were used NetStumbler and inSSIDer applications for this measurement. The last part of work contains measurement of security mechanisms (WEP, WPA, WPA2) effect to transfer rate from the point of view of the end user. The measurement was realized with Iperf application.
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Modern active elements and their behavior in linear circuit blocks
Kosztyu, Tomáš ; Jeřábek, Jan (referee) ; Koton, Jaroslav (advisor)
The topic of this master’s thesis was a frequency filters and their realization using modern active elements like UVC, UCC, VFA, CFA and OTA. The base point of this thesis was designed frequency filters with these active elements, when the shape of the transfer function will be identical for all structures and compare the characteristics of active elements. The proposed frequency filters are second order with one or two active elements. In the first part of thesis are discussed basic properties of frequency filters, their properties and distribution. Next are described the general characteristics of active filters and their basic elements such as operational amplifier OTA, VFA and CFA, and recently more frequently used voltage and current conveyor. The second part is the frequency filters designed with these elements is the same transfer function. Subsequently, simulations are done all the filters and obtained the frequency response. Finally, these filters are experimentally made and made practical measurements.
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Design of tunable frequency filters with modern current active elements
Stejný, Jiří ; Herencsár, Norbert (referee) ; Jeřábek, Jan (advisor)
This master´s thesis deals an active elements called digitally controlled current amplifier, multiple-output current follower and its usage in tunable frequency filters. These tunable frequency filters operate in a pure current mode. In the first part of this work are presented the different types of current active elements. Universal current conveyor, multiple-output current follower, digitally controlled current amplifier (UCC, MO-CF, DCCA). In the second part of this work are introduced particular methods of design tunable frequency filters. Special attention is given to using the design method of via autonomous circuits because it is one of the most. In the last part of this thesis are designed and computer-simulated individual multifunction tunable frequency filters with those already active yet elements. These filters were designed via autonomous circuits or modification of existing circuits. The functionality of the proposed filtres have been verified by computer simulation. Snap3 program was used for the symbolic analyse of circuit and OrCad PSpice program was used to simulate the characteristics of multifunction filters.
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Synthetic immittance dipoles using active current elements
Mráka, Michal ; Jeřábek, Jan (referee) ; Koton, Jaroslav (advisor)
This master thesis discusses the design of Synthetic immittance dipoles using active current elements. The introduction presents aktive current elemetns MO-CF and DACA as buildings blocks for analog filters that are able to process signals with frequencies up to ten megahertz. Methods of synthetic elements using active current elements design is described in this thesis.Is resulted from full addmitances net which contains one active current element Subsequently there are designed various types of frequency filters working in current mode. The functionality of designed filters was verified by computer simulation. Selected designed filter were practically verified with commercially available elelments and active element MO-CF. Measurements in the frequency domain were carried on. On all of types of filters are made sensitivity analysis.
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Communiacation software for terminal clients of a Linux server
Hanák, Karel ; Jeřábek, Jan (referee) ; Jelínek, Mojmír (advisor)
The thesis contains a proposal and implementation of an environment convenient for operation of network client applications which use common terminals. It also consists of implemented examples where the way of their usage is presented. The centralized way of communication is the basis. The approach is used also for the possibility of their joining with managing subsystems, i.e. unlimited ways of regulation of systems for real estate management, access to devices, user authority access to access data points to the devices. The environment is based on operation system Linux and database MySQL. Their realization is supposed on a server, in the network environment. This relates also to the overall security policy and this work also focused on social treatment of clients possibilities.
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Security of wireless computer networks IEEE 802.11
Škodák, Jaroslav ; Jeřábek, Jan (referee) ; Koutný, Martin (advisor)
This work describes available and used standards, protocols and mechanisms used to secure IEEE 802.11 wireless networks. In the next section are listed vulnerabilities and possible attacks against different types of security. The principles of individual attacks on authentication, WEP security and WPA/WPA2 personal mode are described and realized using various software especially linux program aircrack-ng. Password for WEP security is obtained by passive eavesdropping data, using ARP replay injection and by creating own frames. The last two methods are used to generate traffic on the network, which is captured and then used to derive the WEP password. By injecting ARP frames, password was found in the number 60 000 captured frames and about 180 000 frames of data was needed for passive method. Decryption of WEP frame was done by fragment and KoreK chopchop attacks. This decrypted frame could be used to create fake frames and obtain WEP password. Brute force attack is realized for security WPA (WPA2) personal mode (often due to lack of strong password) by comparing password (passphrase) from password list. Speed of comparing is about 200 passwords/s.
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Support for instruction in electric fire alarm systems
Macinka, Jiří ; Jeřábek, Jan (referee) ; Burda, Karel (advisor)
The master’s thesis „Support for instruction in electric fire alarm system” describes principles and engineering solution of electric fire alarm system. It is background for activity task about EPS for students in VUT in Brno. It illustrates how to act on this task and configuration fire panel and components EPS with the support of software FSP 5000. The practice contains proposal EPS with support in fire system designer.
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