Analysis of multipath fading on line-of-sight links in the presence of an elevated atmospheric duct

Multipath propagation on microwave line-of-sight links is analysed in the presence of an elevated inversion atmospheric layer and a reflecting earth. A bilinear height profile for the modified refractive index is adopted. Simple mathematical relations are derived for the number of rays hitting the receiver, and a graphical solution is presented for the launching and arrival angles. It is shown that path inclination tends to reduce the number of rays reaching the receiver. When more than three rays are received, signal enhancement, due to ducting, is more likely to occur. On the other hand, signal fading is more probable in the presence of two or three rays