Limit and application range of the slope-diffraction method for wireless communications

We investigate the limitations on the use of the uniform theory of diffraction (UTD) slope-diffraction method for propagation past knife edges. The settled field that is diffracted past rows of buildings, as computed by numerical integration, has the characteristics of amplitude and phase variation with a scale length that is large compared to the wavelength and has small amplitude near the edges. Using this field, it is shown that the error in the UTD slope-diffraction method for diffraction past a final screen is connected with the Fresnel width, as compared to the scale length of the settled field.