Development and validation of non-vertical cylindrical near-field scanning technique

An alternative cylindrical scanning technique is suggested which aims at increasing the measurement speed and minimizing the vibrations due to the acceleration and the deceleration of the rotating antenna under test during the on-ground RF testing of large spaceborne antennas. Such scanning is implemented by rotating the antenna continuously over the rotational axis (/spl phi/-axis) while scanning along the linear axis (z-axis) simultaneously. This produces data collected over non-vertical lines located on the measurement cylinder compared to the conventional method when the rotational axis is stepped producing data on a rectangular grid. This paper describes a spectral domain technique to reconstruct the near-field data on rectangular grid from data collected along the non-vertical lines. The antenna radiation pattern thereafter is evaluated from the reconstructed near-field data. Preliminary results from this work were reported in the past, in which the validation of this technique was based on the comparison between the near-field data from conventional scan and these reconstructed from non-vertical scan. This left some uncertainty about the success of the technique for near-field data set truncated on /spl phi/. In this paper, the far-field cuts evaluated from the simulated near-field data are used to judge the success of the technique and the operation of the near-field simulation package. The NIST cylindrical near-field software was integrated with the package to calculate the far-field.