Comparing between current and field basis functions in moment method solutions

The center fed disk antenna is used for comparing between the known moment method (MM) solution based on expanding the surface current density J
_ρ
(ρ) on the disk, and the proposed MM expansion of the field component E
_ρ
(ρ) outside the disk, on the disk plane. It is shown that for R <; λ, 3 current basis functions or 3 field basis functions are enough for excellent convergence of the solution. However, for R >; λ, more current basis functions are needed for getting a reasonable solution, while 3 field basis functions are enough for getting accurate solutions, where R is the radius of the disk and λ is the wavelength. CST software simulations are in good agreement with the MM results.