Calculation of radiowave attenuation due to rain at frequencies up to 1000 GHz

Problems in calculating appropriate values of specific rain attenuation for application to the design of communications system are analyzed. A set of design curves based on Mie scattering theory and the Laws Parsons dropsize distribution is presented for the frequency range 1 to 1000 GHz. These curves allow the temperature dependence of rain at the lower frequencies to be taken into account more simply than at present. The possibility of extrapolating the calculations for 'Laws and Parsons' rain to rainrates of 400 mm/h is discussed. On the basis of multiple scattering theory, it is shown that the so-called 'single scattering theory' actually includes all the forward multiple scattering processes, and that is only these processes which contribute significantly to the coherent wave. The effect of the backward multiple scattering processes neglected in the normal calculation procedure is illustrated numerically.