| Summary: | Studying high-latitude travelling ionospheric disturbances (TIDs) is of importance be-cause they often correspond to space weather events which affect the earth's climate. The South African National Space Agency (SANSA) plans to install a low-powered high frequency (HF) transmitter at the South Pole for use in a bistatic ionospheric sounding system intended to detect such TIDs. The aim of this dissertation was to design a suitable transmitter antenna such that propagating skywave signals could successfully be received by the SANAE SuperDARN radar some 2090 km away. A transmitter beacon with an operating frequency of 12.57 MHz and a maximum 1 W power output has already been designed previously for the system. A highly directional antenna was required to reduce interference with another existing SuperDARN radar situated at the South Pole Observatory. A key goal was to transmit as little power as possible, with mainly narrowband antennas being taken into account. Additionally, a wide azimuth beamwidth was desired to allow for the possible illumination of other nearby Antarctic SuperDARN stations. The rest of the parameters were not defined explicitly and were established during the design process. More specifically, the antenna gain, elevation beamwidth and transmitter power required to achieve successful communication had to be determined. A thorough investigation of HF ionospheric propagation was undertaken, with the po-lar ionosphere and its impact on system functionality being of particular concern. Freely available propagation prediction tools were reviewed and ICEPAC was selected for use based on its high-latitude capabilities. It was discovered that the models used in both ICEPAC and the online Virginia Tech SuperDARN ray tracer ignore the presence of the extraordinary wave mode, the significance of which was discussed. The non-deviative radiowave absorption in the D and lower E layers of the ionosphere is one of the most notable contributors to total transmission loss. Consequently, manual calculations of ...
|
|---|