Data reduction in the NF-FF transformation technique with spherical scanning

A fast, accurate and stable two-dimensional sampling interpolation algorithm is developed to reconstruct the electromagnetic field radiated on a sphere in the antenna near-field region. Its analytical foundation relies on the recent theoretical results concerning the nonredundant field representations on curves and surfaces. The use of an ellipsoid (prolate or oblate) as modelling of the source allows one to reduce the number of required samples with respect to the spherical source modelling that, although more general, becomes redundant when considering antennas having one or two predominant dimensions. The obtained results are properly used to get ready an effective near-field-far-field transformation technique with spherical scanning, which requires a minimum number of data, thus reducing significantly the memory storage requirements and measurement time. Numerical examples assess the efficiency and the stability of the reconstruction process.