Fading measurements on a 11 GHz, 31-km terrestrial path at Madras, India

An attempt is made for the first time in Southern India to study systematically the fading observed over an 11 GHz microwave link. The fading characteristics of Puducherry - Madras show a definite diurnal and seasonal variation of the received signal and fading patterns. Correlation of meteorological parameters indicated that the observed fading is mostly due to the super refraction which is caused due to sea breeze effect. Multipath fading and scintillation fading observed over this microwave link have been identified and explained on the basis of movement of atmospheric boundary layer. During the entire period of line-of-sight measurements, three types of fading patterns (classified on the basis of long term median values and fade depths) have been found to occur. The observed fading patterns have been discussed in the light of two-ray theory as well as on the concept of multipath propagation. The fade depths of 1 to 2 dB can be explained on the basis of interference between direct ray and ground reflected ray.