Microwave propagation attenuation due to earths atmosphere at very high frequency (VHF) and ultra-high frequency (UHF) bands in Nsukka under a clear air condition

Abstract

The microwave propagation attenuation due to earth's atmosphere under a clear-air condition for fade depth of 10 dB was investigated using refractivity data calculated from weather vagaries measurement carried out between January and December 2008. The International Telecommunication UnionRadiocommunication Sector (ITU-R) model for multipath fading for small percentage of time with link distance of 100 km was used. The result showed that at this distance, the refractivity gradient has a strong correlation of 0.747 with percentage of time that the fade depth was exceeded. It was also observed that the percentage of time that the fade depth was exceeded increases with frequency until about 1.2GHz when the result becomes unreliable.

Determination and Comparative Analysis of Refractivity Profile and Fade Depth for Microwave Links in Lagos

“…Polynomial models in the frequency domain (complex polynomials, real polynomials of amplitude and group delay) iii. Parametric models (two point method with fixed frequency spacing The impact of this kind of multipath on terrestrial point-to-point microwave links was studied by Bell laboratories in the 1960s and 1970s [6]. Over the years, different models have been developed for predicting the multiple propagation effects on terrestrial links.…”

“…According to research findings, microwave radio propagation is in greater extent affected by meteorological and terrain conditions [1,2,3]. Particularly, the refractive index of the atmosphere which is the key medium of propagation varies with atmospheric height [4,5] The the refractive index affects the magnitude of the multipath fade depth that microwave signal can experience in a given terrain [6,7]. Also, terrain elevation profiles and other site specific feature affect the multipath fade depth.…”