  Next 5G and beyond applications have brought a tremendous interest towards
array systems employing an extremely large number of antennas, so that the
technology that might be in place for communication can be also exploited for
positioning. In particular, in this paper we investigate the possibility to
infer the position of an omnidirectional transmitter by retrieving the
information from the incident spherical wavefront through its EM processing.
Despite such a post-processing of the curvature wavefront has been mainly
considered in the past at microwave and acoustic frequencies using extremely
large antennas, it is of interest to explore the opportunities offered in the
context of next 5G and beyond systems. Thus, differently from the
state-of-the-art, here we first introduce a dedicated general model for
different EM processing configurations, and successively we investigate the
trade-off between the attainable positioning performance and the complexity
offered by the different architectures, that might entail or not the use of a
lens, that can be either reconfigurable or not. Indeed, we analyze also the
effect of the interference, in order to evaluate the robustness of the
considered system to the presence of multiple simultaneous transmitting
sources. Results, obtained for different number of antennas, i.e., for
different array apertures, confirm the possibility to achieve interesting
positioning performance using a single antenna array with limited dimensions.
