COMBINING THE MOMENT METHOD WITH GEOMETRICAL MODELING BY NURBS SURFACES AND BEZIER PATCHES

Induced current distributions on conducting bodies of arbitrary shape modelled by NURBS (Non Uniform Rational B-Splines) surfaces are obtain ed by using a Moment Method approach to solve an Electric Field Integr al Equation (EFIE). The NURBS surfaces are expanded in terms of Bezier patches by applying the Cox-de Boor transformation algorithm. This tr ansformation is justified because Bezier patches are numerically more stable than NURBS surfaces. New basis functions have been developed wh ich extend over pairs of Bezier patches. These basis functions can be considered as a generalization of ''rooftop'' functions. The method is applied to obtain RCS values of several objects modelled with NURBS s urfaces. Good agreement with results from other methods is observed. T he method is efficient and versatile because it uses geometrical model ling tools that are quite powerful.