An analysis of simplified solutions for multiple knife-edge diffraction

A consideration of the diffraction angles used for the case of two knife-edge obstacles shows the pessimism of the solution proposed by Deygout in the determination of the total path loss when the hills have the same individual loss and are close to each other. This consideration is used to discuss a new approximation to compute the multiple diffraction losses of VHF/UHF radio waves over sharp ridges or hills, which yields very good estimates of the received signal level. The analytical basis for the method of Deygout, taking into account the rigorous spectral diffraction theory outside the transition regions surrounding the shadow boundaries, is used to explain the suggested modification. Two example paths are presented and an error smaller than 0.9 dB between the predictions and the measured values has been reported.