A novel approach to high frequency diffraction from curved, perfectly conducting cylinders

Abstract

Discusses diffraction from singly curved surfaces. Diffracted fields can be defined as a correction to those generated by physical optics (PO). These diffracted fields are generated by events local to the shadow boundary of the curved surface therefore knowledge of local radius of curvature at the shadow boundary will give accurate diffracted fields for any arbitrarily shaped curved surface. Knowledge of surface currents allows for the prediction of fields everywhere outside of the curved body. Once the diffraction currents, exact surface current minus PO current, are known total fields can be generated for any arbitrarily shaped, singly curved surface by adding simple PO currents to the diffracted current. To predict these currents a macromodel of the surface diffraction currents, due to plane wave excitation, for the perfect electric conducting (PEC) case is developed. These diffraction currents are from the exact eigensolution for circular cylinders at oblique incidence. Approximate algebraic, expressions, based on the high frequency behavior of the surface fields, are generated by a curve fit to match the exact diffraction current. Expressions are macromodeled for both the TE and TM case and the formulations were split into two regions: (1) 1/spl lambda/</spl alpha/<20/spl lambda/, and 2) 15/spl lambda/</spl alpha/. The curve fit was performed for cylinders up to /spl alpha/=200/spl lambda/, where /spl alpha/ is the cylinder radius, and the macromodeled current was validated up to /spl alpha/=400/spl lambda/ by a comparison with the eigensolution distributions.