NIST adds key capability to atom-based radio communications

April 07, 2021 // By Jean-Pierre Joosting
NIST adds key capability to atom-based radio communications
Benefits of atom-based communications systems include antennas and receivers with micrometer-scale dimensions and less susceptiblity to some types of interference and noise.

An atom-based sensor that can determine the direction of an incoming radio signal has been demonstrated by researchers at the National Institute of Standards and Technology (NIST) and collaborators. The sensor is 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 the 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.

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. Image courtesy of NIST.

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

Picture: 
Image courtesy of NIST.

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