How orbital angular momentum modes are boosting the performance of radio links

Abstract

This paper focuses on the application of orbital angular momentum (OAM) modes for enhancing radio communications. It is shown that OAM modes can enhance the spectral efficiency of line-of-sight links where there is limited or no diversity gain, and also increase physical layer security. Multiple-input multiple-output (MIMO) systems, in comparison, can struggle to give spectral efficiency improvements in line-of-sight links because they are not typically configured to exploit OAM modes. The concept of specifically using OAM modes shows great promise provided that several challenges are addressed. This paper aims to clarify OAM in the context of applications to which it is well suited, such as high capacity point-to-point links alongside transport infrastructure, within data centres, and between buildings.

Performance analysis of an orbital angular momentum multiplexed amplify-and-forward radio relay chain with inter-modal crosstalk

“…In [16], a crosstalk level of better than −13 dB was achieved. None of these studies use partial aperture sampling as an OAM mode filter, which is what has been used for obtaining measured crosstalk here and reported in [9]. Thus, the measured crosstalk levels here may be improved by: using full aperture sampling, careful link alignment and by reducing mutual coupling between antenna elements through careful design.…”

“…As is the case for MIMO, it has the potential to support several parallel data streams by sending each stream on a separate ‘mode’. In this case, a mode relates to the radiated spatial amplitude and phase patterns as defined by the family of Laguerre–Gaussian (LG) beams [9], where the phase signatures are mutually orthogonal [10]. Owing to the phase trajectory of each mode having a ‘twist’, they are shown to have a topological charge and hence referred to as OAM modes [11].…”

Evaluation of the Laguerre–Gaussian mode purity produced by three-dimensional-printed microwave spiral phase plates

“…The LG beam then carries orbital angular momentum (OAM) with a non-zero LG mode number that is characterized by a helical phase front with the axis of rotation along the boresight, or direction of propagation. The screw discontinuity of the phase pattern results in a doughnut-like profile of the magnitude of the beam, with a null magnitude along the boresight [ 1 , 2 ]. The helicoid shape of the wavefront has a step λ / l , where λ is the wavelength and determines the rotational mode (topological charge of the phase vortex) with an azimuthal structure related to exp ( il φ), where φ is the azimuthal coordinate [ 1 , 3 ].…”

Systematic parameter study of orbital angular momentum based radio communication using mixed‐mode matrix

“…OAM waves employed to transmit a wireless signal in an orthogonally polarised channel in the far‐field range [11]. Since OAM was first adopted to radio frequency applications using circular array antennas [12, 13], it has been applied to increase the data rate of wireless communication [14, 15]. OAM was considered an alternative for conventional multi‐input‐multi‐output (MIMO)‐based communication systems [16].…”