Abstract
Rapidly growing demand for channel capacity and limitations in satellite power and frequency spectrum is urging the utilisation of higher frequency bands. Attentions are focused on 20/30 GHz and above which will provide many services due to large the available bandwidth and small size of earth segment. However, the main problem revolves around the severe attenuation by hydrometeors, specifically rain which significantly degrades communications quality. The available propagation data in 20/30 GHz bands in Europe is not sufficient for designing reliable communication systems. Olympus provides a unique opportunity for collection of long term propagation data to investigate the effects of hydrometeors at 12.5, 20 and 30 GHz. An experimental arrangement has been established for 20 GHz beacon measurements at the University of Surrey. Copolar and cross polar measurements were taken but only the copolar attenuation data has been analysed. On 29th May 1991 Olympus lost attitude and orbit control. In its absence the Russian satellite (MAYAK) transmission was recorded, after modification in the receiving equipment. Data recorded from the MAYAK beacon had large cyclic variation, a peak to peak variation of several decibels was observed which were removed at the data preprocessing stage. A limited data was collected from MAYAK since Olympus was restored in mid August 1991 and beacon measurements were continued as before. A few significant propagation events recorded using MAYAK are also presented in the thesis. Olympus showed peak to peak diurnal variation of few decibels which was removed by the data pre-processing software before any statistical analysis of the data. Another experimental arrangement for collection of weather data has also been established. A new time integration technique for calculation of rain rate using low resolution rain gauge has been introduced which produced better results and they were verified using rain attenuation prediction models. The limited data set obtained from Olympus and MAYAK beacons was compared with rain attenuation models as well as European and UK experimental results. Cranes rain attenuation prediction for Guilford yielded best fit to the measured data. There is also a good correlation with the other European measurements. However, comparison with the BTRL was not in full agreement because the BTRL measurements were taken uninterruptedly over a period of one year while the measurements taken at Guildford were short term and interrupted several times due to loss of Olympus, software and hardware development for alternative satellite. Long term data is required for more meaningful comparison. The system has been developed to receive and record data reliably. Data recording is in continuous progress more than one year's data has been obtained but only preliminary recorded data is analysed in this thesis.