Far-field time-domain calculation from aperture radiators using the FDTD method

It is often desirable to determine the far-field radiation pattern from an aperture in a metal plate. The use of time-domain methods, like the finite-difference time-domain (FDTD) method, is problematic because of the necessity of modeling the entire space of interest. This is often circumvented by using the equivalence principle to determine the far field by equivalent currents generated in the near field. However, these transformations are often mathematically complex. This paper presents an extremely simple formulation for calculating the time-domain fields from some types of aperture radiators. By using wavelet analysis, the pertinent parameters can be compressed and stored to be used later to resynthesize the radiated fields.