Full-Wave Planar Near-Field Measurement Simulation Using Vivaldi Antenna as a Probe

In this paper, a new approach for planar near-field (NF) measurements for lower band 5G applications is presented employing a customised Vivaldi antenna as a near-field probe. The paper includes a careful analysis of the impact that the absorber collar has on the overall measurement performance of the probe. A 5G, 24-elements, C-band, planar array antenna has been used as an antenna under test (AUT). Full-wave three-dimensional computational electromagnetic simulations (CEM) of the production test, measurement, and calibration of a given planar-near-field measurement setup with, and without, absorber collar, have been undertaken. Here, special attention has been paid to a thorough examination of the presence of scattering, and the standing waves in the simulated near-field measurement. The presence and impact of this phenomenon has been carefully inspected by intensive simulations and compared with results obtained for a standard open-ended waveguide probe (OEWG) probe, as well as with an alternative dielectric probe. The obtained results have demonstrated clear advantages when compared to the alternative solutions with superior results being obtained in terms of the scattering performance. Standing waves and ripple are found to be far less visible with the overall results after probe compensation being noticeably improved when compared with the more commonly used alternatives. We complete this study by verifying the suitability of the proposed Vivaldi probe for Spherical NF measurements by comparing its spherical mode coefficients with that of the ubiquitous OEWG. In conclusion, the Vivaldi probe spans several waveguide bands, and is suitable for planar, cylindrical, and spherical near-field testing applications.