  A short range experimental communication system, based on Orbital Angular
Momentum (OAM) multiplexing, is presented. We characterize circular arrays of
patch antennas designed to transmit and receive OAM electromagnetic fields,
reporting new results on communication links based on such antennas. We also
experimentally study the antennas tolerance to misalignment errors (angular
tilt and lateral shift) within which OAM multiplexing can be efficiently
exploited. Starting from these results, we finally propose an application to
short range communications of OAM-based systems that can lead to a high level
of security in the information exchange.
