Shadow boundary incremental length diffraction coefficients (SBILDCs) are h
igh-frequency fields designed to correct the physical optics (PO) field of
a three-dimensional (3-D) perfectly electrically conducting scatterer. The
SBILDCs are integrated along the shadow boundary of the 3-D object to appro
ximate the field radiated by the nonuniform shadow boundary current (the di
fference between the exact and PO currents near the shadow boundary), This
integral is added to the PO field to give an approximation to the exact sca
ttered field that takes into account both PO and nonuniform shadow boundary
currents on the scatterer. Like other incremental length diffraction coeff
icients, any SBILDC is based on the use of a 2-D canonical scatterer to loc
ally approximate the surface of the 3-D scatterer to which it is applied. C
ircular cylinder SBILDCs are, to date, the only SBILDCs that have been obta
ined in closed form. In this paper, these closed-form expressions are valid
ated by applying them for the first time to a 3-D scatterer with varying ra
dius of curvature-the prolate spheroid. The results obtained clearly demons
trate that for bistatic scattering the combined PO-SBILDC approximation is
considerably more accurate than the PO held approximation alone.