Spherical Near Field offset measurements using downsampled acquisition and advanced NF/FF transformation algorithm

Spherical Near Field (NF) measurements are widely used in order to accurately characterize the radiating performance of antennas. The main drawback of this type of measurement is the acquisition time that, depending on the electrical size of the Antenna Under Test (AUT), could be very long. This is due to the fact that, in order to correctly evaluate the Far Field (FF) with the NF/FF transformation [1]-[3], the NF has to be sampled over the full sphere with a sampling density that increases with the dimension of the so called AUT minimum sphere [3]. In many spherical NF measurement scenario, it is not possible to locate the AUT in the origin of the measurement sphere resulting in a larger minimum sphere, which implies a denser sampling and a longer acquisition time. An innovative NF/FF technique that allows to drastically reduce the samples density in offset spherical NF measurement is presented in this paper.