The Use Of Digital Signal Processing in Satellite Communication

Abstract

The recent emphasis on Information Technology has increased the need for methods of data communications with a greater interest in the areas of Satellite communications. Data communications over a satellite can be easily achieved by the use of excessive power and bandwidth but efficient management of the satellite resource requires more elegant means of transmission. The optimum modulator and demodulator can be described by mathematical expressions to represent the physical processes that are required to transmit and receive a signal. Digital Signal Processing circuits can be use to implement these mathematical functions and once correctly designed are not susceptible to variations in accuracy and hence can maintain an accurate representation of the mathematical model. This thesis documents an investigation into the algorithms and techniques that can be used in the digital implementation of a Satellite Data Modem. The technique used for carrier phase recovery and data decoding is a major variation on a method proposed by Viterbi and Viterbi and relies on Phase Estimation instead of the more common carrier regeneration techniques. A computer simulation of this algorithm and its performance is described and the overall performance of the simulation is compared to theoretical analysis and experimental performance of a Multi-Data Rate Satellite Modem covering data rates in the range 16 Ksymbol/sec to 256 Ksymbol/sec in both the BPSK and QPSK data formats.