Accurate and efficient evaluation of fields radiated at arbitrary distances by numerically-defined currents residing on arbitrarily shaped objects

In this paper, we present a method to accurately and efficiently compute the radiation from a numerically-defined set of currents represented in terms of a modified version of the classical rooftop basis functions. The shape of the scatterer is completely arbitrary and may be defined by NURBS surfaces [4], Since a NURBS representation is used in most of the CAD design software, this formulation enables us to directly connect the output of the CAD software with the EM solver. The field radiated by each of the modified rooftops is computed in a closed form which does not exhibit the strongly singular behavior of the nearfield Green´s function.