Quasi-Fractal UCA Based N-Dimensional OAM Orthogonal Transmission

TL;DR

This paper introduces an N-dimensional quasi-fractal UCA antenna design that surpasses traditional limits on OAM-modes, enabling higher spectrum efficiency in wireless communications through novel multiplexing schemes.

Contribution

It proposes a new fractal UCA antenna structure and N-dimensional OAM modulation/demodulation schemes to exceed the conventional OAM-modes limit based on array-elements.

Findings

Higher spectrum efficiency achieved in simulations.

OAM-modes number exceeds array-elements limit.

Effective N-dimensional multiplexing demonstrated.

Abstract

The vortex electromagnetic wave carried by multiple orthogonal orbital angular momentum (OAM) modes in the same frequency band can be applied to the field of wireless communications, which greatly increases the spectrum efficiency. The uniform circular array (UCA) structure is widely used to generate or receive vortex electromagnetic waves with multiple OAM-modes. However, the maximum number of orthogonal OAM-modes based on UCA is usually limited to the number of array-elements of the UCA antenna, leaving how to utilize more OAM-modes to achieve higher spectrum efficiency given a fixed number of array-elements as an intriguing question. In this paper, we propose an Ndimensional quasi-fractal UCA (ND QF-UCA) antenna structure in different fractal geometry layouts to break through the limits of array-elements number on OAM-modes number. We develop the N-dimensional OAM modulation (NOM) and demodulation (NOD) schemes for OAM multiplexing transmission with the OAM-modes number exceeding the array-elements number, which is beyond the traditional concept of multiple antenna based wireless communications. Then, we investigate different dimensional multiplex transmission schemes based on the corresponding QF-UCA antenna structure with various array-elements layouts. Simulation results show that our proposed schemes can obtain a higher spectrum efficiency.