Abstract :
The letter proves that two distinct methods of calculating the radiation pattern of a spherical-aperture distribution are mathematically equivalent, i.e. by a spherical-harmonic expansion or by Silver´s far-field formula. The merits of each method and their extension to arbitrary-shaped apertures are briefly discussed. Finally, some results based on these methods and other examples serve to illustrate that involved computer calculations can give rise to errors of the order of typical experimental errors.
