Abstract: Two-level discrete complex image method(DCIM) is used to compute the closed-form Green's functions efficiently. The generalized Pencil-of-Function method is employed to approximate the spectral domain Green's functions by a linear combination of exponential functions. With the Sommerfeld identity, the spatial domain closed-form Green's functions are obtained. In the two-level DCIM, the approximation is performed at two levels to reduce the time to fit the Green's functions with exponential functions so that the efficiency is improved. Numerical results show that the two-level DCIM is an efficient method for calculating the closed-form Green's Functions.

Key words: spatial Green's functions, discrete complex image method, generalized pencil-of-function