ITU model for multi-knife-edge diffraction

An investigation of the ITU recommendation for computing the effects of multiedge diffraction is presented. The ITU formulas are originally given for propagation over terrain. The results show that the original ITU formulas must be modified slightly to agree with the analytical result for the special case of grazing angle over a series of equidistant knife-edges having equal heights. The modified formulas, here called ITU2 formulas, provide the correct analytical results even for a very large number of edges. The ITU2 formulas remain simple to apply for the case of multiple knife-edges with unequal heights and separations. Sample results are provided for these noncanonical cases and show an expected sensitivity on the heights of the edges. A comparison with other methods or measurements remains to be performed.