  Following on from the increasing interest for electromagnetic waves carrying
Orbital Angular Momentum (OAM), different configurations of antenna systems
able to generate such beams have been proposed. However, in our opinion, a
traditional radiation pattern approach does not provide the right picture of an
OAM-based communication link. For this reason we propose a new general concept,
the "OAM-link pattern", which takes into account the peculiar phase structure
characterizing these waves. Focusing on OAM transmissions between antenna
arrays, we introduce a formula for the link budget evaluation which describes
the whole communication link and directly leads to a "classically shaped" main
lobe pattern for a proper rephased reception in the case of uniform circular
arrays.
