Truncation Mitigation Using the Holographic PNF Filter

Author: Scott T. McBride
Publication: AMTA 2024
Copyright Owner: NSI-MI Technologies

Planar near-field (PNF) acquisition always samples a limited or truncated subset of the infinite plane in front of an antenna under test (AUT). That truncation of the sampled field has two primary impacts: Power radiating to or from angles beyond the probing boundary is not fully captured and thus not included and erroneous ripple is injected throughout the pattern when the transformation algorithm sees by default a sudden drop to zero power beyond that boundary.

The topic of truncation mitigation in the PNF geometry has been addressed with a variety of algorithms. This paper introduces a new algorithm that is similar to, yet distinct from, some that have come before. The new algorithm makes use of the recently introduced holographic PNF filter [1][2][3], treating the trunca-tion effects like stray signals. Where the most common technique [2][4] uses the known planar-AUT bounds (2D) and a computed “valid region” of the plane-wave spectrum as truth through iterative transformations, this algorithm treats as truth the known AUT volume (3D) and the measured PNF data. The new algorithm is evaluated herein by retruncating a large set of measured PNF data.

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