Characterisation of building reflection and scatter of microwaves using Fresnel-Kirchhoff diffraction theory

Abstract

Fresnel-Kirchhoff diffraction theory, in essence physical optics, has been used to predict building reflection and scatter Bramely and Cherry (1) and Noerpel (2). Its strength in near and very near fields was clearly demonstrated by comparisons between predictions and measurements made on a number of buildings Al-Nuaimi and Ding (3). This method nevertheless involves complex surface integrals which are computationally expensive particularly for large buildings. For purposes of radio system planning, simple engineering prediction models are much desirable. In this paper, expansions of the Fresnel integral are approximated based on the very near field characteristics of buildings reflection and scatter concluded from the predictions and measurements (3). Building reflection and scatter patterns are expressed as simple functions of angle and distance dependencies. In comparison with the results of measurements and predictions of the more complete Fresnel-Kirchhoff method (3), validity of the model is assessed in presence of building features and background scatters which are not accounted for in this simple solution.