Spherical Near-Field Far-Field Techniques

Spherical wave expansions are well suited to transform measured near-field data of an antenna to far-field data. In this paper a comparison between techniques for obtaining spherical wave expansions from near-field measurements is presented. The techniques are compared with respect to requirements on measuring time, computer storage, computer time and disk storage. It is concluded that the iterative method, Ludwig [2], and the Fourier expansion method, Wacker [5], offer nearly the same upper limit of the size of the antenna under test. Further, it is found that the iterative method requires a higher number of measuring points.