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NIST demonstrates sensor that determines direction of incoming radio signal

Posted: 05 Apr 2021 07:36 PM PDT
http://feedproxy.google.com/~r/kb6nu...m_medium=email


From the National Institute of Standards and Technology (NIST), April 5,
2021.

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
theÂ*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 researchersÂ*previously demonstratedÂ*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 benefitÂ*5G and beyond,â€� 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 onÂ*advanced communications, including
5G, the fifth-generation Â*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 theÂ*NIST on a
ChipÂ*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 forÂ*lengthÂ*andÂ*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.Â*Applied Physics Letters.Â*Published online
March 15, 2021. DOI:Â*10.1063/5.0045601

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