Tech
Dan Romanchik KB6NU
[A real article, not April fool]
NIST demonstrates sensor that determines direction
of incoming radio signal
Posted: 05 Apr 2021 07:36 PM PDT
NIST researchers and collaborators determined the direction of an incoming radio signal based on
laser measurements at two locations in this sensor filled with a gas of cesium atoms. Credit: NIST
Researchers at the National Institute of Standards and Technology (NIST) and collaborators have
demonstrated an atom-based sensor that can determine the direction of an incoming radio signal,
another key part for a potential atomic communications system that could be smaller and work
better in noisy environments than conventional technology.
NIST researchers previously demonstrated that the same atom-based sensors can receive commonly
used communications signals. The capability to measure a signal’s “angle of arrival” helps ensure the
accuracy of radar and wireless communications, which need to sort out real messages and images
from random or deliberate interference.
“This new work, in conjunction with our previous work on atom-based sensors and receivers, gets us
one step closer to a true atom-based communication system to benefit 5G and beyond,” project
leader Chris Holloway said.
In NIST’s experimental setup, two different-colored lasers prepare gaseous cesium atoms in a tiny
glass flask, or cell, in high-energy (“Rydberg”) states, which have novel properties such as extreme
sensitivity to electromagnetic fields. The frequency of an electric field signal affects the colors of light
absorbed by the atoms.
An atom-based “mixer” takes input signals and converts them into different frequencies. One signal
acts as a reference while a second signal is converted or “detuned” to a lower frequency. Lasers
probe the atoms to detect and measure differences in frequency and phase between the two
signals. Phase refers to the position of electromagnetic waves relative to one another in time.
The mixer measures the phase of the detuned signal at two different locations inside the atomic
vapor cell. Based on the phase differences at these two locations, researchers can calculate the
signal’s direction of arrival.
To demonstrate this approach, NIST measured phase differences of a 19.18 gigahertz experimental
signal at two locations inside the vapor cell for various angles of arrival. Researchers compared these
measurements to both a simulation and a theoretical model to validate the new method. The
selected transmission frequency could be used in future wireless communications systems, Holloway
said.
The work is part of NIST’s research on advanced communications, including 5G, the fifth-generation
standard for broadband cellular networks, many of which will be much faster and carry far more
data than today’s technologies. The sensor research is also part of the NIST on a Chip program,
which aims to bring world-class measurement-science technology from the lab to users anywhere
and anytime. Co-authors are from the University of Colorado Boulder and ANSYS Inc. in Boulder.
Atom-based sensors in general have many possible advantages, notably measurements that are
both highly accurate and universal, that is, the same everywhere because the atoms are identical.
Measurement standards based on atoms include those for length and time.
With further development, atom-based radio receivers may offer many benefits over conventional
technologies. For example, there is no need for traditional electronics that convert signals to
different frequencies for delivery because the atoms do the job automatically. The antennas and
receivers can be physically smaller, with micrometer-scale dimensions. In addition, atom-based
systems may be less susceptible to some types of interference and noise.
________________________________________
Paper: A.K. Robinson, N. Prajapati, D. Senic, M.T. Simons and C.L. Holloway. Determining the Angle-of-
Arrival of a Radio-Frequency Source with a Rydberg Atom-Based Sensor. Applied Physics Letters.
Published online March 15, 2021. DOI: 10.1063/5.0045601
The post NIST demonstrates sensor that determines direction of incoming radio signal appeared first
on KB6NU's Ham Radio Blog.