Near- and far-field calculations in FDTD simulations using Kirchhoff surface integral representation

Kirchhoff's surface integral representation (KSIR) is used to calculate the near and far fields from the finite difference time domain (FDTD) simulation. The KSIR is very simple to implement and its distinct advantage is that the calculation of any of the six field components depends on the value of the same field component over a closed surface. This avoids interpolation errors when using the popular Yee scheme for FDTD. In addition to its efficiency and simplicity of implementation, the KSIR leads to highly accurate near fields that reduce absorbing boundary condition (ABC) errors.