New Sensor Uses Atoms to Receive Commonly Used Communications Signals

At the National Institute of Standards and Technology (NIST), scientists have demonstrated an innovative sensor that utilizes atoms to obtain signals that are commonly used.

When compared to traditional radio receivers, the new, atom-based receiver could be made smaller and can operate better in noisy settings among other potential benefits.

The NIST researchers employed cesium atoms to obtain digital bits (that is, 0s and 1s) in the most standard communications format, which, for instance, is used in satellite TV, cell phones, and Wi-Fi.

In this communications format, known as phase modulation or phase shifting, numerous electromagnetic waves, including radio signals, are shifted in relation to each other over time. This data or information is then encoded in this modulation.

The point is to demonstrate one can use atoms to receive modulated signals. The method works across a huge range of frequencies. The data rates are not yet the fastest out there, but there are other benefits here, like it may work better than conventional systems in noisy environments.

Chris Holloway, Project Leader, NIST

As illustrated in the latest paper, signals based on real-world phase-shifting techniques were received by the quantum sensor. A 19.6-GHz transmission frequency was easy for the experiment and hence this was selected; however; it can also be utilized in upcoming wireless communications systems, stated Holloway.

Earlier, the NIST researchers employed the same basic method for imaging as well as measurement applications. Two different color lasers were used by the researchers to prepare atoms restricted in a vapor cell into high-energy (Rydberg) states, which have unique characteristics like extreme responsiveness to electromagnetic fields. The colors of light absorbed by the atoms are affected by the frequency of an electric field signal.

In the latest experiments, the researchers used a newly developed atom-based mixer to change the input signals into new frequencies. While one radio-frequency (RF) signal serves as a reference, the second RF signal acts as the modulated signal carrier. Variations in frequency and offset amid the two signals were identified and determined by studying the atoms.

In the past, several scientists have demonstrated that atoms can receive other formats of modulated signals, but the NIST group was the first to create an atom-based mixer that has the potential to handle phase shifting.

Based on the encoding scheme, the atom-based system received approximately 5 megabits of data per second. This speed is close to that of older, third-generation (3G) mobile phones.

In addition, the scientists determined the precision of the received bit stream predicated on a traditional metric known as error vector magnitude (EVM). In EVM, a received signal phase is compared to the optimized state and this helps in gauging the modulation quality. In the NIST experiments, the EVM was less than 10%, which is sufficient for an initial demonstration, stated Holloway. He added that this is similar to systems deployed in the field.

A few commercial devices like chip-scale atomic clocks are already using tiny lasers and vapor cells. This suggests that the development of practical atom-based communications equipment may well be viable.

According to the paper, additional advances could make atom-based receivers to deliver several advantages over traditional radio technologies. For example, conventional electronics that change signals into different frequencies for delivery are no longer required because the job is automatically done by atoms.

Both receivers and antennas can be physically tinier having very small dimensions. Atom-based systems may also be less sensitive to certain types of noise and interference. In addition, the atom-based mixer can accurately determine weak electric fields.

Researchers are currently planning to enhance the latest receiver by decreasing other unwanted effects, including laser noise.