Antenna titling as a measure to reduce fading on microwave line-of-sight links

Multipath fading is a major factor degrading the performance of microwave line-of-sight links operating below 10 GHz. Vertical variations in radio refractivity cause the microwave beam to travel in more than one path. These additional paths are generated by propagation phenomena like ground reflection, reflection from one or more layers in the atmosphere or scattering from inhomogeneities giving rise to deep fades at the receiver. Fading mechanisms characterised by the path geometry, meteorological conditions, operating frequency, and the type of fading pattern observed at the receiver, if they are explored thoroughly, a fading remedy can be suggested. Sometimes multipath fading can be reduced or controlled by the judicious siting and positioning of antenna. In 1986 the microwave propagation group at the National Physical Laboratory had undertaken a study to investigate the deep fadings encountered on a line of sight microwave link situated in Northern India. The detailed investigation of the deep fadings encountered on the Delhi-Meerut link, possible remedial measures to overcome the fading from the radio meteorological point of view, and the implementation of the above remedial measures are presented