GNSS Reconfigurable Antenna Design for Multipath Characterization

Reference stations are a critical element of the GNSS infrastructure and provide valuable measurements for constellation monitoring [1]. It is however important to obtain high-quality measurements from these stations and therefore any kind of local error source shall be minimized or properly accounted for. When choosing the site for a new reference station or when analyzing the performance of a current one, particular attention shall be devoted to multipath. The multipath (and a poor suppression of it) is one of the major error sources and can lead, in an extreme case, to non-usability of measurements of the reference stations' network and/or to the need of expensive countermeasures to be put in place after installation [2]. Currently, however, there is, to the authors' best knowledge, no scientific way to assess the multipath conditions of a given site before installation of a new antenna. It was demonstrated in previous work from the authors [3] that the amount of multipath available at the receiver in a given installation site strongly depends on the so-called antenna "multipath suppression capability indicators" (MPSI). Antennas with similar MPSIs placed in the same position are expected to deliver similar amount of multipath error to the receiver. It is therefore feasible to perform a generic characterization of the site by using a reconfigurable "probe" antenna, capable of assuming different levels of MPSI. The results obtained by this set of measurements will then form a sort of "database of multipath" for the site for each MPSI level. Such technique will then allow to foresee beforehand the performance obtainable with any other antenna, just by comparing its MPSI values with the multipath obtained with a corresponding MPSI of the "probe antenna". This paper will show the design of the reconfigurable antenna. The results of the electromagnetic measurement of the antenna will also be shown together with the different values of MPSI achievable by reconfiguring the antenna. Moreover, MPSI values from different commercial antennas will be derived for comparison. An experimental validation of the method will be reported, in which the multipath probe antenna will be used to estimate the multipath environment in a given site.