Accurate and computationally efficient chararterization of near- and far-fi
eld radiation from a class of microwave, millimeter wave, and ultrafast sys
tems is presented. A numerical technique is utilized which combines the fin
ite-difference time-domain method with a spatial transformation, the Kirchh
off surface integral. Included in the analysis are inhomogeneous material p
arameters, small feature size relative to wavelengths of interest, and the
wide-band nature of the radiation. Based on simulation results, a simple mo
del of the radiation from an inhomogeneous structure is del eloped. Finally
, the technique is applied to accurately characterize the radiation from a
photoconducting structure.