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Title: Investigation into the effect of refractivity on propagation at UHF and VHF frequencies – modelled and experimental analysis
Author: Alam, Imtiaz
ISNI:       0000 0004 5356 1987
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2015
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The goal of this research was to use weather parameters to compute refractivity variation of the atmosphere that can be used to predict refractivity distribution in the first kilometre of the atmosphere over the English Channel for UHF and VHF propagation and to understand the influence of meteorology on propagation. Different refractivity profiles are constructed based on meteorological data taken from the UK Meteorological Office in order to investigate their effects on wave propagation. The hourly experimental path loss between the transmitter and receiver obtained from the experimental setup comprising of two UHF and two VHF communication links are investigated for a period of one year. The experimental setup comprises of long and short trans-horizon paths (140 km and 50 km) having a transmitter located on Jersey and receivers on Portland and Alderney. In order to investigate the characteristics of refractivity and its impact on wave propagation, a propagation model is developed in MATLAB using parabolic equation method. The model is used to get an hourly modelled path loss corresponding to the experimental path loss for four communication links of UHF Portland, UHF Alderney, VHF Portland and VHF Alderney. The correlation between the modelled path loss and experimental path loss is presented for refractivity distribution recommended by the ITU and for that of a standard atmosphere. The simulated and experimental results showing the influence of evaporation duct upon path loss for frequencies of 240 and 2015 MHz is also included. The results obtained by using the standard atmospheric refractivity profile were a better fit to the experimental observations than the ITU recommended values for some of the investigated links. It is also inferred that evaporation ducts exist up to a height of 10 m for the short path at both frequencies and up to a height of 30 m for the long path at VHF but not at UHF.
Supervisor: Siddle, David; Warrington, Michael Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available