Sphiral near-field scanning for automotive antenna measurements

Spherical spiral (Sphiral) scanning involves coordinating the motion of two simultaneous axes to accomplish near-field antenna measurements along a line on a sphere that does not cross itself. The line would ideally start near a pole and trace a path along the sphere to the other pole. An RF probe is moved along this path in order to collect RF measurements at predefined locations. The data collected from these measurements is used along with a near-field to far-field transformation algorithm to determine the radiated far-field antenna pattern The method for transforming data collected along a sphiral scan has been previous presented [12, 13]. Later laboratory measurement studies have shown the validity of the technique [23]. A review of the sphiral scanning technique and its recent advances, resulting from about ten years of research collaboration between the UNISA Antenna Characterization Research Group and MI Technologies is here presented. Such a scan technique relies on the non-redundant sampling representations of EM fields and takes full advantage of moving two axes simultaneously. Accordingly, it allows one to drastically reduce the overall number of required data and the time to collect the data. This scanning technique can be properly applied in testing antennas mounted on automobiles in order to reduce the overall time of the measurement.