Orbital angular momentum multiplexing

Orbital angular momentum (OAM) multiplexing is a physical layer method for multiplexing signals carried on electromagnetic waves using the orbital angular momentum of the electromagnetic waves to distinguish between the different orthogonal signals. Orbital angular momentum is one of two forms of angular momentum of light. OAM is distinct from, and should not be confused with, light spin angular momentum. The spin angular momentum of light offers only two orthogonal quantum states corresponding to the two states of circular polarization, and can be demonstrated to be equivalent to a combination of polarization multiplexing and phase shifting. OAM on the other hand relies on an extended beam of light, and the higher quantum degrees of freedom which come with the extension. OAM multiplexing can thus access a potentially unbounded set of states, and as such offer a much larger number of channels, subject only to the constraint of real-world optics. The constraint been clarified in terms

The Orbital Angular Momentum (OAM) Multiplexing Controversy: OAM as a subset of MIMO

Joana Rita Alves dos Santos Silva, Santiago Capdevila Cascante, Juan Ramon Mosig, Julien Perruisseau-Carrier, Michele Tamagnone

Recently the orbital angular momentum (OAM) multiplexing scheme has been proposed to increase supposedly without limit the channel capacity between a transmitter and a receiver nodes communicating in line of sight. A controversy arose about the far-field effectiveness of this method and about it being or not a subset of MIMO communication schemes. In this contribution we first illustrate that OAM multiplexing can be completely understood as line of sight MIMO, and hence that the technique cannot bring additional advantages in far-field communications. Secondly, we show that it is possible to build similar line of sight near field MIMO systems based on lenses which perform better than their OAM counterparts.

2015

Electromagnetic Inspired Acoustic Metamaterials

Seyyed Hussein Seyyed Esfahlani

This thesis deals with electromagnetic inspired acoustic metamaterials, enabling sound-matter interactions in different wave scenarios that include propagation, guided-waves, radiation, refraction, reflection and transmission. To this end, a particular emphasis is placed on introducing novel applications for acoustic metamaterials operating on each one of the aforementioned wave scenarios. A few years ago, metamaterials have been introduced as a new class of composite artificial materials, engineered to produce unusual effective material properties not readily available in nature. Electromagnetic metamaterials are probably the oldest class of metamaterials, being nowadays in the process of reaching maturity and being proposed for interesting commercial applications. On the other hand, as in most young but not yet mature emerging fields of science, acoustic metamaterials are still providing lots of fertile and unexplored ground for research and study. Despite many inherent physical differences, the propagation of electromagnetic and acoustic waves are both governed by a similar mathematical model, the so-called Helmholtz wave equation. The main purpose of this work is to leverage this amazing similarity by translating recent advances in electromagnetic metamaterials into their corresponding, previously unseen, applications in acoustics. The first contribution of this thesis is to adapt the classic electromagnetic transmission-line theory to allow the design of acoustic metamaterials. The proposed circuit-based theory finds a direct application in the design of composite right/left hand transmission-line metamaterials, which yield novel guided-wave applications for acoustic metamaterials. Then, the developed theory is leveraged to model and achieve optimal design of different acoustic metamaterial-based devices, such as leaky-wave antennas and reflector-type metasurfaces. The second part of the thesis spins around acoustic leaky-wave antennas and their different functionalities, showing that they are able to act as acoustic dispersive prisms in the refraction mode and as acoustic single sensor direction finder in the radiation mode. Studying reflection phenomena in sound-metasurface interactions constitutes the next part of this thesis, where a membrane-capped cavity is introduced performing as an ultra-thin unit-cell for reflective acoustic metasurfaces. This leads to exciting applications of the concept, like acoustic reflectarray antennas and acoustic metasurface skin-cloaks Finally, the last part of this thesis deals with transmission phenomena in acoustic metasurfaces and, especially, in orbital angular momentum metasurfaces. This concept results in the design of an innovative labyrinthine-type helicoidal unit-cell that is used for phase coding a surface and transforming impinging acoustic wavefronts into transmitted helical wavefronts.

EPFL2017

Pattern-reconfigurable built-in antenna for data multiplexing with a single radio

Julien Perruisseau-Carrier, Mohsen Yousefbeiki

Beam-space multiplexing has been demonstrated as a promising approach for transmitting multiple signals while using a single RF chain. This paper presents a novel beam-space antenna design that is very compact and integrated into a hypothetical portable platform. To provide required pattern reconfigurability, two silicon p-i-n diodes are used as the sole needed mounted elements, resulting in simpler reconfigurable loads and DC bias networks compared to previous works. A fully-operational antenna prototype is fabricated and measured, showing excellent agreement between simulations and measurements. The antenna can be used for single-radio multiplexing of two BPSK signals, enabling MIMO transmission in reduced-complexity hardware for future wireless applications.

IEEE2013

Electromagnetic Inspired Acoustic Metamaterials

Seyyed Hussein Seyyed Esfahlani

EPFL2017