Probe Positioning Error Sensitivity Analysis for Planar Near-field Antenna Measurements

Unmanned aerial vehicle based field measurements have been proposed as a possible solution to provide calibration data for large ground based radio telescope arrays, such as the Mid Frequency Aperture Array planned for the Square Kilometre Array project. This paper considers planar near-field scanning using a quad-copter equipped with a differential GPS (DGPS). The effect of random positional errors associated with DGPS on two different near- to far-field (FF) transformations, namely the planar plane wave expansion (PPWE) and the Fast Irregular Antenna Field Transformation Algorithm (FIAFTA), are investigated in the frequency range 450 MHz-1450 MHz. It is shown that FIAFTA drastically outperforms the PPWE for the given situation and produces adequate results over the band for a positional error of 1 cm. However, considering positional inaccuracies of 5 cm, both algorithms produce a predicted FF pattern which is corrupted beyond being of any practical use.