Recent advances in antenna measurement techniques at the DTU-ESA spherical near-field antenna test facility

This paper reports recent antenna measurement projects and research at the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark. High-accuracy measurement projects for the SMOS, SENTINEL-1, and BIOMASS missions of the European Space Agency were driven by uncertainty requirements of a few hundredths of dB for the directivity and correspondingly strong requirements for gain and/or phase. Research and development of 1:3 bandwidth range probes, and the near-field to far-field transformation algorithm accounting for the higher-order azimuthal modes in the spherical wave expansion of such probes, are also reported. Also, a metamaterial-inspired super-directive first-order probe enabling small-sized probes at low frequencies, such as P-band, is reviewed.