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Forecasting Of Micro Wave Fading Through Meteorological Parameters: A Model Computation

Abstract

The rapid fluctuations of troposphere in certain cases pose serious problems in achieving microwave communications and there are situations when the line-of-sight (LOS) link may deviate from the expected path of propagation. LOS microwave links though found to be reliable and widely used but the tropospheric medium through which the signal propagates is found to create problems in such links. Bending of LOS path from its desired trajectory along with deviation in angle-of-arrival of the signal causes much degradation in the energy levels of the signal in well designed links.In this paper effort has been made to predict fade depth of a microwave signal of frequency less than 10 GHz. through a model associating with the Radio Refractive Index gradient (RRI grad), which is a function of temperature, pressure, humidity.The RRI is calculated at the surface, at 100 meters, and 500 meters height levels. In case where RRI increases or decreases uniformly then the slope is defined by a single parameter ‘N1’ . But for a non uniform atmosphere another parameter ‘N2’ is introduced. Here N1 is the RRI grad between the surface and 100m. and N2 is the RRI grad for upper atmosphere. Model is then developed correlating different situations of the atmosphere (whether n1 or N2 is in normal, sub refractive or super refractive state 0 with the fade depth of a 16 km, 6 GHz line of sight microwave link in the suburban Kolkata circle

S.Duttagupta, T.R.Ghosh

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