Diffracted Fields on a Building Rooftop Considering Reflection by Ground and Building Rooftop

In order to have an effective utilization of the radio wave resources, it is important to estimate propagation path in the urban area. In our previous work, we have examined the diffracted fields by two edges with an arbitrary angle. In this paper, the characteristics of the diffracted fields by two horizontal edges of a building rooftop are discussed for two cases: a building without or with parapets. We also consider the effects of reflection by a rooftop and the ground. The numerical calculations are carried out for two edges of a conducting or concrete building rooftop. The results show that the waves grazing on the rooftop of concrete building are considerably attenuated for the low conductivity, but when parapets are constructed on the rooftop, the diffracted waves become stronger than the grazing waves. The effect of the field reflected by a rooftop for diffracted field by two parapets is small. When the incident wave is horizontally polarized, the reflected field by ground is strong, but for vertical polarized incidence, the ground reflection is weak.