Measurements of low gain VHF antennas in spherical multi-probe NF system

The accurate characterization of low-gain antennas at VHF frequencies is challenging. Such antennas can be tested outdoors for convenience or in very large and thus expensive indoor Far-Field (FF) ranges [1]. Indoor Near-Field (NF) systems are often considered a better cost compromise for such measurements, mainly due to the relaxed requirements on chamber size. However, reflectivity issues and other source of errors such as truncation can compromise the measurement accuracy [2]. Multi-probe NF systems in spherical geometry are optimal measurement solutions for the low frequency characterization of low directivity antennas such as most antennas in automotive applications [3,4,5]. In this paper, we present VHF-band measurements of a low directivity antenna in a hemispherical and quasi full-3D multi-probe system. The VHF antenna in this study is an array element, which has been developed for space applications [6-7]. The different measurements reported are part of the technology development activity of the antenna. For each antenna measurement, the gain and pattern accuracies are investigated by comparison with full wave simulations.