ITU-R P.526-16 (11/2025)

Recommendation ITU-R P.526-16 (11/2025) Propagation by diffraction
Foreword
Policy on Intellectual Property Right (IPR)
Scope
Annex 1
1 Introduction
2 Basic concepts
2.1 Fresnel ellipsoids and Fresnel zones
2.2 Penumbra width
2.3 Diffraction zone
2.4 Obstacle surface smoothness criterion
2.5 Isolated obstacle
2.6 Types of terrain
2.7 Fresnel integrals
3 Diffraction over a spherical Earth
3.1 Diffraction loss for over-the-horizon paths
3.1.1 Numerical calculation
3.1.1.1 Influence of the electrical characteristics of the surface of the Earth
3.1.1.2 Diffraction field strength formulae
3.1.2 Calculation by nomograms
3.2 Diffraction loss for any distance at 10 MHz and above
4 Diffraction over isolated obstacles or a general terrestrial or Earth – space path
4.1 Single knife-edge obstacle
4.2 Single rounded obstacle
4.3 Double isolated edges
4.4 Multiple isolated cylinders
4.5 Method for a general terrestrial path
4.5.1 Bullington model
4.5.2 Complete method
4.6 Method for a general Earth – space slant path
4.6.1 Bullington model for an Earth – space slant path
4.6.2 Effective plane-Earth model
4.6.3 The complete slant-path model
5 Diffraction by thin screens
5.1 Finite-width screen
5.2 Diffraction by rectangular apertures and composite apertures or screens
5.2.1 Diffraction by a single rectangular aperture
5.2.1.1 Fresnel integral method
5.2.1.2 Semi-empirical method
5.2.2 Diffraction by composite apertures or screens
6 Diffraction over a finitely conducting wedge
7 Guide to propagation by diffraction
Attachment 1 to Annex 1 Calculation of cylinder parameters
1 Diffraction angle and position of vertex
2 Cylinder parameters
Attachment 2 to Annex 1 Sub-path diffraction losses
1 Introduction
2 Method

This Recommendation presents several models to enable the reader to evaluate the effect of diffraction on the received field strength.