Combined Mie series and asymptotic formulation of transient scattered field and perfectly conducting sphere

The transient scattered field by a perfectly conducting sphere in the backward and forward directions has been calculated by evaluating the Bromwich integral for the inverse-Laplace transform. Substantial reduction in the computation time can be achieved by using asymptotic representation in the high-frequency region while retaining the Mie series solution in the low-frequency segment of the contour. The locations of the transition to the asymptotic form are determined by the accuracy required. Their effects are studied by numerical computations. An error analysis made on the backscattered field revealed that a total relative energy error of less than 5% can be achieved with substantial reduction in computation time by means of this method.<>