MANUSCRIPT ACCEPTED FOR PUBLICATION IN IEEE TRANSACTIONS ON ANTENNAS ANDPROPAGATION (SEE COPYRIGHT NOTICE ON PAGE 1)
Is orbital angular momentum (OAM) based radio communication an unexploited area?
Ove Edfors, Member, IEEE, and Anders J Johansson, Member, IEEEAbstract—We compare the technique of using the orbital angular momentum (OAM) of radio waves for generating multiple channels in a radio communication scenario with traditional multiple-in-multiple-out(MIMO) communication methods. We demonstrate that, for certain array conﬁgurations in free space, traditional MIMO theory leads to eigen-modes identical to the OAM states. From this we conclude thatcommunicating over the sub-channels given by OAM states is a subset of the solutions offered by MIMO, and therefore does not offer any additional gains in capacity. Index Terms—Antenna arrays, antennaradiation patterns, channel capacity, free-space propagation, MIMO, orbital angular momentum, radio communication.
I. I NTRODUCTION T WAS recently shown that the photon orbital angular momentum (OAM)can be used in the low frequency radio domain and is not restricted to the optical frequency range . These ﬁndings and the claimed prospects for opening a new frontier in wireless communications,with “promise for the development of novel information-rich radar and wireless communication concepts and methodologies” , motivates the investigation in this paper. Here we focus on the wirelesscommunication aspects of  and the follow-up paper . We start by identifying the conditions under which electromagnetic waves with speciﬁc OAM characteristics1 are generated in   and continueby comparing with properties of traditional communication using multiple-in-multiple-out (MIMO) antenna systems   . We pay special attention to the singular value decomposition (SVD) based...