Software for Fresnel-Kirchoff Single Knife-Edge Diffraction Loss Model

Abstract

In this paper, development of software for computing single knife-edge diffraction loss based on Fresnel-Kirchoff model and Lee’s analytical approximation model is presented. The mathematical expressions and algorithm for the single knife edge diffraction loss software are presented. The input required by the software includes frequency, height of the transmitter and receiver antennas, height of obstruction, distance of the obstruction from the transmitter or receiver. The output includes diffraction loss, Fresnel diffraction parameter, path length and phase difference between the direct and diffracted paths, the number and radius of all Fresnel zones block by the obstruction. Moreover, the software is used to study the variation of diffraction parameter, diffraction loss and other link parameters with obstruction height. Results are presented in tables, graphs and also as a list of parameters and their values. Sample diffraction loss computation is conducted for a 9GHz microwave link with 25 m knife edge obstruction. At diffraction parameter of 5.4772255575 the corresponding diffraction loss is -27.72756218 dB. More importantly, at diffraction parameter of 0 (zero) the corresponding diffraction loss is -6.02 dB which is in agreement with the published works on single knife edge diffraction loss at diffraction parameter of 0 (zero).

Keywords

• Diffraction Loss
• Diffraction Parameter
• Diffraction
• Single knife Diffraction
• Fresnel Zone
• microwave Link
• Line-Of-Sight Link