The aim of this work is to propose the involvement of a monitoring receiver for air band and its practical realization. The receiver is controlled from a PC via USB, after which it is transmitted simultaneously digitized audio signal. The receiver can be controlled from a PC, or some basic function by buttons.

The aim of this thesis is to innovate NCL 07 unit made by NAM system a.s. The new device is intended to have improved parameters and diminished dimensions. It should be fully comparable to similar products on market. In the first part there are described features and individual circuits of NCL07 unit. Further there is done an analysis to suggest modifications leading to reduce proportions of DPS and to enhance other parameters including SW design improvement. Theoretical part deals with selection of main measured values and methods of verification of measurement accuracy. There is also described theoretical basis used in the oncoming sections of the thesis. In the practical part there are presented procedures of designs of innovated product. In the conclusion there will be made testing of new unit and results will be compared to competitive commodities.

The main topic of this master´s thesis is a practical simulation of wireless mobile networks. For this purpose, the model simulating urban enviroment in which mobile nodes move according to desgined trajectories was created. The parameters of transmitted signal and impact of obstacles in the way of propagation were examined by the simulation. Number of obstacles and type of material of given obstacle was taken into consideration.

This thesis deals with demodulation, decoding RDS messages and an FM receiver in FPGA. It is the processing of data after A/D conversion of radio stereo signal. This work contains detailed theoretical knowledge of the RDS system, of the individual types of messages, their demodulation and subsequent decoding of individual services. There is theoretically analyzed in FPGA platform and implementation of RDS System and FM receiver.

This thesis analyzes the problem of design analog fiber optic link for transmission high frequency signals. Analog fiber optic link will be used in system for detection and localization a partial discharge activity MOSAD-PD-UHF, where will replace existing solution with coaxial cables, which is not appropriate for highly noise environment. MOSAD-PD-UHF system is developed in department of theoretical and experimental electrical engineering. At the first, MOSAD-PD-UHF system and individual parts of optical chain are theoretical described. In following part are compared a few commercially available analog fiber optic link and design of chosen transmit and receive module are described. . The thesis final part deals with construction of optical link and measured parameters are discussed.

Concern over the altering climate due to the release of anthropogenic greenhouse gases has caused a major shift in the developments of ways to minimise human impact on the climate. Solar energy is seen as one of the most promising sources to transform the energy market for low-carbon energy generation. Currently, solar power is generated via photovoltaic (PV) and concentrating solar power (CSP) technologies. The advantage of CSPs to scale up renewable energy to utility level, as well as to store thermal energy for electrical power generation when the sun is not available (after sunset or during cloudy periods) makes this technology an attractive option for sustainable clean energy. CSP development, however, is still in its infancy, and for it to be a competitive form of energy-generation technology, techno-economic developments in this field need to improve the efficiency and decrease the costs of this technology. A policy report by the European Academies’ Science Advisory Council (EASAC) (2011) indicated that central receiver (solar tower) CSP systems show the greatest margin for technological improvements (40% to 65% is estimated), and that an improvement in receiver technology could make the greatest contribution to increase efficiency. This study therefore focused on analysing the optical and thermal performance of a new proposed solar cavity molten salt receiver design for a central receiver CSP system using a numerical approach. In this study, the receiver’s performance was analysed by first selecting an existing heliostat field, Planta Solar 10 (PS-10). For the numerical analysis to reflect conditions that are as realistic as possible, numerical models for different aspects were selected and validated. For modelling the sun, the solar tracking numerical model proposed by Iqbal (1983) was selected and implemented after literature and comparison showed adequate results. The direct normal irradiation (DNI) was modelled by applying a clear sky model, with the parameterisation model C proposed by Iqbal (1983) as the chosen model. The variables in this model that were subject to temperature, and humidity values were more accurately presented by adding numerical approximations of the region’s actual weather data. The DNI model reflected realistic fluctuations. For the thermal modelling, a validation study was conducted on impingement flow heat transfer to select an appropriate Reynolds-averaged Navier-Stokes (RANS) model that would provide accurate results when conducting the thermal performance test on the receiver. The study concluded that the transitional Shear Stress Transport (SST) turbulence model performed the best. A new method was also developed and validated that allows one to not only simulate complex geometries within the Monte Carlo ray tracing environment SolTrace, but also to apply the results obtained by simulating this model as a heat source within the computational fluid dynamics (CFD) environment ANSYS Fluent. This allows SolTrace modelling to be more accurate, since models do not need to be approximated to simple geometries. It also provides an alternative for solar modelling in ANSYS Fluent. The optical analysis was conducted by first performing an analysis on the receiver aperture and studying its sensitivity on the captured flux. This was followed by analysing the optics of the proposed receiver, the flux distributions on a simplified absorber surface area, and how these distributions are altered by changing some parameters. An in-depth analysis was finally done on the absorber area by applying the aforementioned model to simulate complex geometries within SolTrace, with the results illustrating the difference of the detailed geometry on optical modelling. An alternative receiver design with improved optical features was proposed, with an initial study providing promising results. The thermal analysis was done within the CFD environment, with only a section of the absorber surface area considered, and by applying the solar flux simulated during the optical analysis as heat source within the geometry model. This allowed the model to simulate the effects of re-radiation at the surface of the absorber while simulating the heat transfer at the fluid molten salt side simultaneously. The results showed that, for the current design and requirements, the absorber surface temperature reaches impractical temperatures. Altering the design or being more lenient on the requirements has, however, shown dramatic improvements in terms of thermal performance. Sensitivity studies for both the optical and thermal analyses have shown that changes in design can dramatically improve the performance of the design, making it a possible feasible receiver design for central receiver systems. / Dissertation (MEng)--University of Pretoria, 2019. / National Research Foundation (NRF) / Mechanical and Aeronautical Engineering / MEng / Unrestricted

GNSS (Global Navigation Satellite System) är system som gör det möjligt för en mottagare att känna sin position. Det täcker över GPS (Global Positioning System), ett system som drivs av USA, Galileo (europeisk), Beidou (kinesiska) och andra.För närvarande, med en fristående GPS-mottagare, är noggrannheten på positionen runt 1m. Men, GNSS-signaler förändras vid spridning genom atmosfären och kan brytas, reflekteras eller sprids av den närliggande miljön av mottagaren. Dessa bidrag (respektive kallade atmosfärsfördröjning och flervägsfel) leder till fel i mottagarens positionsskattning. Målet med denna studien är att presentera metoder för att hantera dessa fel. / GNSS (Global Navigation Satellite System) is a system that allows a receiver to know its position. It includes GPS (Global Positioning System), a system designed by the United States, Galileo (European), Beidou (Chinese) and others.Currently, with a stand-alone GPS receiver, the accuracy on the position estimation is around 1m. Indeed,GNSS signals are altered when spreading through the atmosphere and can be diffracted, reflected or scattered by the nearby environment of the receptor. These contributions (respectively called atmospheric delay and multipath) lead to errors on the receiver position estimation. The goal of this study is to present methods in order to tackle these errors.

An impinging type solar receiver has been designed for potential applications in a future Brayton Solar Dish System. The EuroDish system is employed as the collector, and an externally fired micro gas turbine (EFMGT) has been chosen as the power conversion unit. In order to reduce the risks caused by the quartz glass window, which is widely used in traditional air receiver designs, a cylinder cavity absorber without a quartz window has been adopted. Additionally, an impinging design has been chosen as the heat exchange system due to its high heat transfer coefficient compared to other single-phase heat exchange mechanisms. This thesis work introduces the design of an solar air receiver without a glass window, which features jet impingement to maximize the heat transfer rate. A detailed study of the thermal performance of the designed solar receiver has been conducted using numerical tools from the ANSYS FLUENT package. Concerning receiver performance, an overall thermal efficiency of 72.9% is attained and an output air temperature of 1100 K can be achieved, according to the numerical results. The total thermal power output is 38.05 kW, enough to satisfy the input requirements of the targeted micro gas turbine. A preliminary design layout is presented and potential optimization approaches for future enhancement of the receiver are proposed, regarding local thermal stress and pressure loss reduction. This thesis project also introduces a ray-thermal coupled numerical design method, which combines ray tracing techniques (using FRED®), with thermal performance analysis (using ANSYS Workbench).

Unknown wireless devices that use receiver architectures with a mixer may be detected and located using stimulated emissions. Transmitting a known stimulation signal and correlating leaked mixer products allows measurement of the TOF and thus range. The FRFT improves the detection of the stimulated emissions by compressing the energy of the stimulated emissions to a single axis value. The stimulation signal has many parameters that may be optimized for maximum detection distance or minimum range error or somewhere in between. The primary limiting factor for the parameters is the processing time, as the algorithm to compute the discrete FRFT is computationally intensive at the time of this report. The tests performed in this investigation achieved 45+meters detection distance with < 3 meters of range error, with potential for farther detection distance.

The demand for outdoor precise location is increasing with the development of new applications such as autonomous vehicles, exploration robots and wireless sensor networks. Global Navigation Satellite System (GNSS) is the go-to system for outdoor localization. This thesis focuses on developing new methods for GNSS single-point positioning (SPP) model, where no access to a reference station or precise GNSS parameters is needed. We investigated the limitations of the standard method, least- squares adjustment (LSA), and we derived the Cramer-Rao bounds for the SPP estimation problem. We also investigated different techniques to formulate the positioning problem with the goal to increase the accuracy. A new method is developed by reformulating the problem as difference-of-convex program (DC program) and utilizing convex-concave procedure (CCCP) to solve the positioning problem without linearizing the observation equations. In addition, we examined the potential of multiple-receiver systems in increasing the accuracy. We formulated the multiple- receiver SPP estimation problem, and we proposed to configure the multiple receivers in a fixed equilateral triangle to exploit the symmetry and the geometrical constraints of the configuration. We extended the use of LSA in multiple-receiver system. We also developed a modification of LSA algorithm, named least-squares adjustment extension (LSAE), that utilizes attitude information and the constraints of the multiple-receiver system. In addition, we developed a new algorithm to optimizes the SPP estimates over the equilateral triangles Riemannian manifold, which enforces the geometrical constraints of the multiple-receiver system. Furthermore, we derived the constrained and the unconstrained Cramer-Rao bounds (CRB and CCRB) for the multiple-receiver SPP problem. Moreover, we investigated the influence of both attitude information and the equilateral triangle baseline length on the algorithms’ performances and the derived CCRB. Finally, we carried out a numerical analysis by implementing the algorithms and the bounds in MATLAB, where we tested the algorithms on simulated GNSS scenarios. The proposed multiple-receiver methods provide more precise estimates for the SPP problem in comparison to the single receiver methods.