A Comparison of Near-Field to Far-Field Transformation Techniques For Use With Industrial Multi-Axis Robotic Antenna Measurement Systems

This paper compares and contrasts a number of different near-field to far-field transformation algorithms that can be used for the purpose of processing near-field data acquired using multi-axis industrial robots. The merits and limitations of these various, commonly encountered algorithms are highlighted with comparison far-field data presented across a frequency range spanning 3 to 15 GHz. Crucially, the paper explores the viability of using mixed mode acquisition geometries when performing antenna gain measurements where, prior to this work, several of the transforms yielded different transform gains, and electrical lengths. Here, we verify that at 8 GHz and above, where truncation effects were minimal, for this circa 30 dBi gain (at 8 GHz) test antenna the far-field peaks were in agreement to better than ±0.02 dB, at 3σ irrespective of the acquisition geometry and transform algorithm used.