Further Exploration of the Holographic PNF Filter
Author: Scott T. McBride
Publication: AMTA 2022
Copyright Owner: NSI-MI Technologies
Abstract — A 2021 AMTA paper introduced a 3D holographic filtering algorithm optimized for the planar near-field (PNF) geometry. This filter has been shown to have an excellent combination of AUT-signal preservation, stray-signal rejection, and processing speed. It requires only the sampling of a conventional PNF measurement, along with a specified 3D boundary surrounding all the AUT’s possible radiating sources.
The 2021 paper suggested some topics for further investigation, specifically the optimal Z spacing through the 3D hologram and the X- and Y-widths of the blanking window’s tapered extension, and those are investigated here. This paper also explores the combination of filtering and probe correction, since the measured convolution of probe and AUT spatial distributions will be wider than that of the AUT by itself. Finally, filter effectiveness is evaluated for different stray-signal locations with respect to the AUT volume.View The Paper