Unique determination of a perfectly conducting ball by a finite number of electric far field data

In this paper,we prove uniqueness in determining a perfectly conducting ball in the inverse electromagnetic scattering problem by a finite number of electric far field patterns with a single incident direction and polarization. It is emphasized that we use only one electric far field pattern datum to uniquely determine the radius of a ball if it is centered at the origin with radius R < 2 / k . Furthermore, if its center was not given as a prior information, three more measurement data must be added to uniquely determine its center. The main tool used here is some new results on zeros of spherical Bessel and spherical Neumann functions.