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Abstract:
The Intel IXP2400 is a powerful and flexible network stream processor which promises to offer superior performance to currently deployed solutions while remaining cost effective. This report presents the design of a Virtual Private gateway based on the IXP2400 processor, implementing a subset of the Internet Protocol Security (IPsec) protocol.
The design is chosen through analysis and comparison of multiple possible designs. Performance of the design is optimised by performing manual design space exploration on a performance critical section of the system.
A framework for performance evaluation by simulation is presented. This framework is used to perform a complete analysis of the performance of the gateway. Performance and Quality of Service factors such as throughput, delay and jitter and measured for a variety of packet loads and configurations.
A complete description of the Internet Protocol Security standard is presented, along with an analysis of the algorithms required for implementation of the standard.
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Abstract:
The purpose of this project is to design and install part of the monitoring electronics required to monitor the status of a Dassaults 400Hz generator system. The temperature of the generator casing heatsink and pressure of the generator air cooling system need to be monitored. The results must be transmitted from the generator by wireless connection to a lab where the monitored characteristics are to be displayed. Research was done to find the most suitable and available components to satisfy the requirements.
The temperature of the generator casing heatsink is fully installed and operational, producing an accurate temperature output reading which is displayed to the user. The air pressure monitoring is designed and operational but not installed because the cooling system has not arrived at UCT yet. Further research and design was done to complete other areas of the monitoring system not stated in the scope of the project.
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Abstract:
This thesis was carried out by Irene Cruywagen under the supervision of Prof. M. Inggs. The terms of reference as drawn up by Irene Cruywagen and her supervisor were as follows:
The broad aim of this thesis was to develop experiments for the EEE 486F course, RF and Microwave Fundamentals, to provide comprehensive tutoring information on the HP 8410 Vector Network Analyser (VNA).
These tutorials and experiments should include the following:
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Abstract:
Polyphase filters are highly efficient structures for channelizing signals. When applied in firmware they are capable of running at very high data rates, owing to the parallelism they allow. This project's primary aim was to develop a firmware-based polyphase filter design tool, using open source tools wherever possible.
The project went through three stages of development: first, mathematical simulations were coded, second, a firmware design was developed and finally, the design was implemented on a USRP GNU Radio board. A simulation environment was developed to create a uniform way of applying and retrieving signals throughout these stages, which aided the testing and analysis of the polyphase filter's design. Potential improvements and optimizations are discussed in the conclusions.
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Abstract:
This report describes the implementation of a MATLAB user interface for the remote operation of an electrical resistance tomography instrument via an IP connection.
MATLAB code together with open source EIDORS reconstruction functions and existing C++ functions have been combined to form an easily modifiable, graphical user interface for data capture and image reconstruction. A description of the present state of the UCT tomography system is presented along mathematical theory used for image reconstruction.
An overview of TCP/IP communication between MATLAB and C++ is presented before the design functionality, coding and implementation of the remote client is discussed. The application of the remote MATLAB client in feedback control for a control volume within the measurement vessel is investigated. Performance testing of both remote imaging and control feedback are discussed. Conclusions are drawn based on these results and improvements recommended.
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Abstract:
This thesis sought to investigate the numerous methods of attaining extended depth of focus with the intention of comparing an implementation of a section of them.
This analysis was done against the backdrop provided in the background to the study. A comprehensive study of the methods relating to an approach consisting of a numerical construction of a single deep focus image from a collection of images obtained by performing mechanical scanning of the specimen on different image planes.
An alternative solution based on the use of a specially designed phase plate to use in the optical path that allows an extension of the depth of focus of the images observable was additionally investigated as well as the use of stereoscopic vision and digital holograms.
The result of the investigation revealed a number of possible approaches to resolving the challenge. Of the methods investigated two were implemented and contrasted against combineZ5, a freely available image processing application designed to enhance Depth of field. The purpose of such an investigation finds meaning against the backdrop provided by a world of technological evolution and the increased need for ubiquitous, low cost and efficient systems.
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Abstract:
This report focuses on the design and implementation of a C-band transceiver for the South African Synthetic Aperture Radar (SASAR II) project. The transceiver transmits and receives a chirp signal at a frequency of 5300 MHz and is designed to replace the existing X-band RF stage and interface with the existing system at an intermediate frequency of 1300 MHz.
A 3W power amplifier was supplied for the transmitter power stage, which required a new power supply unit (PSU) to be designed and built. The completed power supply provided output voltages 5V, 10V, 15V, -15V and ground and could supply up to 2A of current. The frequency distribution unit (FDU) was modified to produce two identical 4000 MHz local oscillator signals at 10 dBm for the up and down-conversion of the signal in the transmitter and receiver.
The power levels in the transmitter were tracked through each component and it was found that the C-band transmitter could interface with the existing system. A budget analysis of the C-band receiver compared favourably with the existing system budget with respect to signal and noise levels.
The transceiver was then designed and simulated using SystemView by Elanix. Given a 100 MHz chirp signal at 158 MHz the transceiver was able to up-convert the signal to 5300 MHz and then down-convert a received signal to 158 MHz. Filtering requirements were met in the simulation.
Components for the C-band transceiver were selected, however, the system was not constructed due to time constraints.
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Abstract:
Magnetic levitation is the process of levitating an object by exploiting magnetic fields. If the magnetic force of attraction is used, it is known as magnetic suspension. If magnetic repulsion is used, it is known as magnetic levitation.
In the past, magnetic levitation was attempted by using permanent magnets. Earnshaw’s theorem however, proves that this is mathematically impossible. There exists no arrangement of static magnets of charges that can stably levitate an object. There are however means of circumventing this theorem by altering its basic assumptions. The following conditions are exceptions to Earnshaw’s theorem:
Electromagnetic levitation works via the magnetic force of repulsion. Using repulsion though makes a much more difficult control problem. The levitating object is now able to move in any direction, meaning that the control problem has shifted from one dimension to three. There is much interest in levitation due to its possible applications in high speed transport technology. These applications can be broadly referred to as MagLev, which stands for magnetic levitation. A system which more closely resembles the work done in this thesis project is the MagLev cradle. The MagLev cradle is a system designed by Bill Beaty. It is able to levitate a small rod magnet for a few seconds at a time. This system suffers from serious instability. As such levitation can only be maintained for a few seconds.
The MagLev cradle utilizes an arrangement of up to 12 electromagnets and their control circuits in a 'v' configuration to levitate a bar magnet. The MagLev cradle uses rapid switching circuits to control current to the electromagnets. If the bar magnet falls too close to the electromagnet, the circuit switches on, thus applying more repelling force. If the bar magnet rises too high above the electromagnet, it turns off, thus removing the repelling force.
The system developed for this thesis uses the position sensing technique employed by the magnetic cradle. Hall Effect sensors are placed on each of the electromagnets in the system. Each electromagnet and its current control circuitry operates as an independent system to levitate part of a bar magnet.
The Hall effect sensor is a device that senses magnetic flux. It is also capable of detecting the magnetic flux orientation. It is placed on an electromagnet to sense the presence of the bar magnet we wish to levitate. The circuitry is configured such that is magnetic flux is detected; the system will energize the electromagnet in order to make the net magnetic flux with the hall effect sensor zero. Therefore this system electronically simulates the Meissner effect by repelling both north and south poles of a magnet. Experiments were also done to investigate various configurations of electromagnets in order to achieve stable magnetic levitation.
This current control circuit for the electromagnets used an opamp summer circuit and a power amplification stage (sink/source transistor circuit). Initial tests revealed that besides position sensing, speed information was required as well. This was achieved by adding a phase lead circuit, which negated the phase lag caused by the electromagnet (an inductive load) and the control circuitry.
Different configurations of electromagnets were used to attempt to levitate a bar magnet. The main problem that was soon identified was that of keeping the levitating bar magnet in the area above the electromagnets. Despite moving the electromagnets closer and further apart, the bar magnet could not be effectively trapped above the electromagnets. The bar magnet has a tendency to 'slide' off the ends, as the end magnets cannot react quickly enough to movements in the bar magnet. Thus current system lacks the control circuitry required to achieve stable electromagnetic levitation.
At present, pairs of electromagnets can effectively levitate part of a bar magnet which is supported at one end. If the necessary control circuit required to effectively hold the levitating bar magnet in position above the electromagnet can be designed, then a working system can be quickly realised.
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This page was last updated in September 2008 (RL)