Propagation studies and modulation techniques for a distributed architecture rural radio-telephone system

Abstract

The work described in this thesis forms part of the development of a novel digital distributed radio network. In particular, the areas of radio propagation and modulation are considered. Field measurements of radio channel characteristics made in Sierra Leone are described. The results are presented, together with a description of the implementation of the measuring equipment. Both transmission loss and channel impulse responses were measured. Measured loss values are compared with theoretical values calculated using standard routines. The measurements were made at a frequency of 53 MHz. The implementation of a spectrally efficient modulation scheme using a power efficient transmitter is detailed. Transmitter linearization schemes are described. Consideration is also given to filtering techniques applicable to look-up table based transmission. An overall transmitter has been produced, operating at 53 MHz, and the results are given