Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2017. / This dissertation presents the development of a quadrature phase shift keying (QPSK) demodulator for nanosatellites that complies with both the limited resources associated with nanosatellites as well as the flexibility and configurability required for a software defined radio (SDR) platform. This research project is a component of a bigger project, which is to develop a high-speed receiver for nanosatellites, and aims to provide a practical solution to the need for communication technologies that support emerging nanosatellite applications, such as Earth observation and communications. The development of the QPSK demodulator follows an all-digital implementation approach. The main reason for selecting this approach is to have a system that is flexible and reconfigurable to comply with the SDR requirements. Another reason for selecting this approach is to comply with the low noise system, low power consumption as well as the small size and weight requirements associated with nanosatellites. The QPSK demodulator is implemented on an IGLOO2 Field Programmable Gate Array (FPGA), due to its robustness to radiation and high-speed capability. Initially, the techniques used to design each subsystem of the QPSK demodulator are selected. Then, algorithms to digitally implement the designed subsystems are produced. Thereafter, the code for the digital QPSK demodulator is written and verified in Matlab first. The simulation of the Matlab-based QPSK demodulator performs satisfactorily. Subsequently, the code to implement the QPSK demodulator on an FPGA (IGLOO2) has been written in Libero, using VHSIC Hardware Description Language (VHDL). The resulting FPGA-based QPSK demodulator has been emulated in Libero (an integration and development environment (IDE) for Microsemi FPGAs) using a test-bench as well as other analysis tools. The test-bench results are visualized using Modelsim. The results show that the demodulator can support data rates up to 13.25 Mbps if 16 samples-per-symbols are used, and up to 26.5 Mbps if 8 samples-per-symbols are used. It also has a very good bit-error-rate performance, which is simulated to be within a factor of 5 of the theoretical limit of QPSK modulation. Finally, the demodulator consumes less than 15 mW at the maximum operating speed. and has been coded to mitigate the effects of space radiation and noise contriution by the demodulator itself.

Tese de Mestrado Integrado. Engenharia Civil - Especialização em Estruturas. Faculdade de Engenharia. Universidade do Porto. 2011

Tese de mestrado integrado. Engenharia Civil. Hidráulica. Universidade do Porto. Faculdade de Engenharia. 2010

Tese de mestrado. Engenharia Electrotécnica e de Computadores (Área de especialização em Sistemas Digitais e Informática Industrial). Faculdade de Engenharia. Universidade do Porto. 2007

Dissertação apresentada para obtenção do grau de Mestre em Engenharia Biomédica (Área de especialização de Sinais e Imagens Médicas), na Faculdade de Engenharia da Universidade do Porto, sob a orientação do prof. Doutor Jorge Alves da Silva

Traditional telephony networks with their cumbersome and costly infrastructures are being replaced with voice being transmitted over the Internet. The Internet is a very commonly used technology that was traditionally used to transmit data. With the availability of large bandwidth and high data rates the transmission of data, voice and video over the Internet is gaining popularity. Voice is a real time application and the biggest problem it faces is the loss of packets due to network congestion. The Internet implements protocols to detect and retransmit the lost packets. However, for a real time application it is too late before a lost intermediate packet is retransmitted. This causes a need for reconstruction of the lost packet. Therefore, good reconstruction techniques are being researched. In this thesis a new concealment algorithm to reconstruct lost voice packets is reported. The algorithm is receiver based and its functionality is based on Time Scale Modifications of speech and autocorrelation of a speech signal. The new techniqhe is named the Modified Waveform Similarity Overlap Add , (WSOLA) technique. All simulations were performed in MATLAB.

The rapid growth of technology in recent decades has changed the whole dimension of communications. Today people are more interested in hands-free communication. In such a situation, the use a regular loudspeaker and a high-gain microphone, in place of a telephone receiver, might seem more appropriate. This would allow more than one person to participate in a conversation at the same time such as a teleconference environment. Another advantage is that it would allow the person to have both hands free and to move freely in the room. However, the presence of a large acoustic coupling between the loudspeaker and microphone would produce a loud echo that would make conversation difficult. Furthermore, the acoustic system could become instable, which would produce a loud howling noise to occur. The solution to these problems is the elimination of the echo with an echo suppression or echo cancellation algorithm. The echo suppressor offers a simple but effective method to counter the echo problem. However, the echo suppressor possesses a main disadvantage since it supports only half-duplex communication. Half-duplex communication permits only one speaker to talk at a time. This drawback led to the invention of echo cancellers. An important aspect of echo cancellers is that full-duplex communication can be maintained, which allows both speakers to talk at the same time. This objective of this research was to produce an improved echo cancellation algorithm, which is capable of providing convincing results. The three basic components of an echo canceller are an adaptive filter, a doubletalk detector and a nonlinear processor. The adaptive filter creates a replica of the echo and subtracts it from the combination of the actual echo and the near-end signal. The doubletalk detector senses the doubletalk. Doubletalk occurs when both ends are talking, which stops the adaptive filter in order to avoid divergence. Finally, the nonlinear processor removes the residual echo from the error signal. Usually, a certain amount of speech is clipped in the final stage of nonlinear processing. In order to avoid clipping, a noise gate was used as a nonlinear processor in this research. The noise gate allowed a threshold value to be set and all signals below the threshold were removed. This action ensured that only residual echoes were removed in the final stage. To date, the real time implementation of echo an cancellation algorithm was performed by utilizing both a VLSI processor and a DSP processor. Since there has been a revolution in the field of personal computers, in recent years, this research attempted to implement the acoustic echo canceller algorithm on a natively running PC with the help of the MATLAB software.

<p>There is a big interest for alternative investment strategies than investing in traditional asset classes. Commodities are having a boom dynamic with increasing prices. This thesis is therefore based on applying Modern Portfolio Theory concept to this alternative asset class.</p><p>In this paper we manage to create optimal portfolios of commodities for investors with known and unknown risk preferences. When comparing expected returns to actual returns we found that for the investor with the known risk preference almost replicated the return of the markets. The other investor with unknown risk preference also profited but not as efficient as the market portfolio.</p>

<p>Discharges of warfare bio aerosol clouds are powerful weapons in war and terror situations. A discharge of a small amount of a contagious substance can obliterate large areas. The discharges can usually not be seen with bare eyes, hence some tool needs to be used to find bio aerosol cloud discharges. One way is to use a lidar for the detection of clouds. By sending out a laser pulse into the atmosphere some of the light is scattered back. By measuring the backscattered light, the aerosol structure of the atmosphere can be obtained. If a cloud is hit by the laser beam, an increase of light is observed and the cloud can be detected and tracked.In this thesis a tool for simulating the elastic backscattered light has been developed. A graphical user interface for easier handling has also been developed. For automatic detection of clouds some detection algorithms have been tested. Another graphical user interface for presentation of the simulated lidar signals has also been constructed.The simulator is working well. A lot of different parameters can be changed for the lidar system, the atmosphere and the cloud type. The model works as a helpful tool for specifications of an elastic lidar system to be developed and also as a guide for expected system performance and ways to present the results.</p>

<p>The object of this thesis is to provide a MATLAB framework for nonlinear filtering in general, and particle filtering in particular. This is done by using the object-oriented programming paradigm, resulting in truly expandable code. Three types of discrete and nonlinear state-space models are supported by default, as well as three filter algorithms: the Extended Kalman Filter and the SIS and SIR particle filters. Symbolic expressions are differentiated automatically, which allows for comfortable EKF filtering. A graphical user interface is also provided to make the process of filtering even more convenient. By implementing a specified interface, programming new classes for use within the framework is easy and guidelines for this are presented.</p>