Far-field reconstruction from a minimum number of spherical spiral data using effective antenna modellings

Two probe-compensated near-field-far-field transformations with spherical spiral scanning tailored for antennas having two of their dimensions very different from the third one are developed by properly applying the unified theory of spiral scans for nonspherical antennas. One is suitable for electrically long antennas, which are considered as enclosed in a cylinder ended in two half-spheres. The other adopts a surface formed by two circular “bowls” with the same aperture diameter but different lateral bends to shape a quasi-planar antenna. These flexible modelings fit very well many actual antennas by properly setting their geometric parameters. Great reduction of the number of data to be acquired is achieved, thus significantly reducing the required measurement time. Numerical tests validating the accuracy of the proposed techniques and their stability with respect to random errors affecting the data are shown.