Efficient Near-Field Far-Field Transformation for Nonredundant Sampling Representation on Arbitrary Surfaces in Near-Field Antenna Measurements

A nonredundant sampling representation on arbitrary surfaces in near-field antenna measurements together with a direct near-field far-field transformation is described. The utilized sampling criterion depends on the electrical size of the antenna under test (AUT) along with the separation between the AUT and the measurement surface. The minimum number of samples required is directly linked with the number of unknowns in the linear system of equations derived considering spherical expansion of radiated AUT fields. Equivalent plane wave sources are used to represent the AUT fields. Plane wave translations can be directly performed for any arbitrary measurement grid with the same efficiency. Thus, nonredundant sampling representations can be utilized on any scan surface. In contrast, other fast field transformation techniques would lose their efficiency. The proposed sampling is applied to near-field measurements and synthetic data using a variety of antennas and the results are compared to the case of standard sampling. Remarkable decrease in the number of measurement points is observed with a negligible change in the accuracy of the transformed pattern, thereby greatly reducing the measurement time and the computational effort.