IMPROVED MODELLING OF HARMATTAN DUST EFFECT ON THE CROSS POLARIZATION OF A MICROWAVE ACCESS RADIO LINK OPERATING BETWEEN 15GHz AND 38GHz BY HENRY AIKHIONBARE

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Department of Engineering

ABSTRACT
Dust carry non-spherical particles which in the absence of turbulence or shear wind and hydrodynamic forces, tend to orient their major axis in the vertical plane, thus resulting in particles anisotropy which may contribute to Cross Polarization Discrimination (XPD) degradation due to differential phase shift. This research presents an improved model of harmattan dust effect on cross polarization of microwave access radio link operating between 15GHz and 38GHz. Meteorological data such as dust mass concentration, visibility, etc. for ten years (that is, 2003 to 2012) were obtained from Nigerian Meteorological Agency (NIMET) and the five months harmattan period data was sorted out. The sorted data were used to deduce important parameters like dielectric constant, relative particle volume and so on. Then, the complex propagation coefficients (attenuation and phase shift) were deduced as a function of wave frequency, media dielectric constant depolarization factor and fractional volume of dust storm using Maxwell’s electromagnetic equation for a random medium. Mathematical background for XPD was then established as a function of signal frequency, dielectric constant of dust storm, particle size probability distribution function and visibility. Finally, a link budget analysis was done for some selected frequency values of 18 GHz, 23 GHz, 27 GHz, 30 GHz and 35 GHZ to deduce a fade margin of 52.073dB, 50.5313dB, 41.2168dB, 43.1843dB, 41.6434dB and 41.3091dB respectively due to the depolarization factor of harmattan period in Kano. A percentage time availability of 99.99 percent was obtained for the selected antenna thereby showing the validity of the developed model based on Rayleigh’s distribution Model for Link availability.