Modelling of dust storms-induced scattering for prediction of cross polarization dicrimination at millimetre wave band

Abstract

Effects of dust storms on the performance of microwave links have received considerable interest in recent decades with emphasis on signal attenuation. However, phase shift and cross polarization have not been tackled enough. In order to address this problem, two topical issues are looked into. The first is modelling of complex scattering induced by dust storm considering dust particle shapes and best fit ellipsoids. The second is prediction of cross polarization discrimination (XPD) using the model parameters as inputs. Three conditions are set to validate the suitability of Rayleigh application method for the model. It has been shown that the Rayleigh approximation is valid for determining the scattering of spherical and ellipsoidal dust particles for the particle sizes and frequency range considered. The scattering coefficients are derived and mathematical models for phase shift and attenuation are proposed in terms of relative permittivity and visibility. Differential phase shift and attenuation are computed and XPD introduced by dust storms in such links are predicted. Attenuation in dry dust is only significant when the visibility becomes severe. Cross polarization becomes significant i.e. numerically low when the visibilities fall below 100m over about 10km path link or below 10m over about 1 km of path. XPD of 21.7dB is recorded at 85 GHz along 1 km of path link. It can therefore be concluded that for dry dust storm, the XPD is fairly good for use in dual polarization systems. The application of the model is however limited to frequency of up to 85 GHz.