An investigation of the mechanism of total internal reflection in tropospheric microwave propagation

Some calculations are performed concerning the amplitude and phase fluctuations of a totally reflected monochromatic and homogeneous radio beam from a monotonically stratified tropospheric layer. In a first approximation the incident beam is considered to be collimated; the reflected beam is then also collimated but inhomngeneous along a cross section parallel to the interface. Next, a more realistic case is considered in which the incident beam is given by an angular bundle of rays corresponding to a certain radiation polar diagram of the transmitting source. Under this condition the totally reflected field presents a more complicated structure in space, since it manifests focusing or defocusing effects not only along the boundary of the layer but also with height from this interface. A numerical evaluation of these fluctuations with height is of special interest; in principle they may justify vertical space diversity efficiency in a number of typical cases concerning more especially obstructed microwave paths.