1. PREDICTIVE METHOD FOR MULTIPLEXING
LAGUERRE-GAUSSIAN BEAMS AT RADIO FREQUENCIES
Motivation
Summary
Acknowledgments
S. Sharma1, H. Yao1, H. Kumar1, T. Ei1, R. Henderson1, S. Ashrafi2, D. L. MacFarlane3, Z. Zhao4, Y. Yan4, A. Willner4
1University of Texas at Dallas, Richardson, TX; 2NxGen Partners LLC, Dallas, TX; 3Southern Methodist University, Dallas, TX; 4University of Southern California, Los Angeles, California.
Background
• Description
• Description
• The multiplexing and de-multiplexing of LG beams are carried out using a toolkit in MATLAB.
• MATLAB results validate hypothesis posed in communication demo.
Future Work
Problem Statement
Proposed Solution
Phase Plots
References
• Laguerre Gaussian beams are higher order Gaussian beams containing
orbital angular momentum.
• Orbital angular momentum (OAM) based communication systems have
been proposed to increase the total channel capacity at radio
frequencies.
• The intensity at the center of a Laguerre Gaussian(LG) beam has a null
giving its intensity pattern as donut shaped.
• The size of the hole along the
axis of the LG beam
increases as the mode
increases.
• Different LG modes are
mutually orthogonal.
• The phase plot of LG modes
are spiral/twisted in shape.
• Using a mathematical model we propose to validate the results
obtained in the ‘Experimental Demonstration of Dual-channel E-band
Communication Link using Commercial Impulse Radios with Orbital
Angular Momentum Multiplexing’.
• Express field equations at each point of the communication link.
• Use MATLAB tools to generate OAM modes at 73GHz and compare to
the demonstration.
• Demonstrate the multiplexing of LG beams at the transmitter and
demultiplexing at the receiver along the same channel
• This demo shows that multiplexing leads to
adding of two beams spatially and
demultiplexing leads to untwisting of beams.
• To provide a numerical technique to support the dual-channel E-band
multiplexing demonstration.
Fig.1: Laguerre-Gaussian Beams
• Build functions to take in account loss,
alignment and zoom factor for the beam.
• Take into account the signal to noise ratio for
successful receiving of the Gaussian beam in
the second channel.
• Using MATLAB toolkit for LG beams, fields are defined at all points of the communication link (figure 2) [1].
• Demo: (1) Generate message signal & modulate on 73 GHz; Using impulse radios, transmit Gaussians on
Ch1/Ch2; (2) Introduce OAM (Twist), Combine & Transmit; (3) Receive, Split and Remove OAM (Untwist); (4)
Measure bit error rate (BER) to confirm communication.
• Hypothesis – We can untwist Ch1 signal back to Gaussian and measure the signal.
• [1]https://www.mathworks.com/matlabcentral/fi
leexchange/15459-basic-paraxial-optics-
toolkit/content/transverse/LaguerreGaussian.m
• Y. Yan, et al. “High-capacity millimetre-wave
communications with orbital angular
momentum multiplexing,” Nature
Communications 5 (2014).
Fig. 3: Dual-Channel Communication Link for Multiplexing & Demultiplexing two LG beams
Fig.4 : Phase Plot
of fields present at
each point of
communication
link
Multiplex LG= +1 & LG = -3
• This work was sponsored by NxGen Partners
LLC.
Example Code
LG= +1Gaussian
LG=-3
Demultiplex (LG +1 and LG-3)* (LG-1)
Gaussian & LG = -4
Fig. 2. Photograph of the experimental setup