A new perturbation approach to quantifying changes in the far field pattern induced by rounding the corners of a scatterer

The electromagnetic fields diffracted by sharp edges and comers have long been understood to be different in character to those scattered by smooth bodies. The nature of the singularities in the field and its derivatives is described in [1], Although analytical and numerical methods for the accurate modelling of these singularities have had substantial development, their implementation can be both time consuming and rather specialised. On the other hand, the large number of readily available general purpose scattering packages generally assume that the scattering surface is smooth, and in order to model scattering from an obstacle with comers it is usually replaced by a smooth scatterer resulting from rounding the comers in some fashion. Although the singularities in the field quantities and surface distributions are thereby eliminated, it is desirable to develop some estimate of the error or difference thus induced.