This breakthrough could not only double traffic in the crowded existing wireless frequencies but could also open up higher millimeter-wave frequencies at 30 GHz and above

By Warren Miller,
contributing writer

A new technique for creating millimeter-wave circulators on
a single chip may make it possible to implement full-duplex or two-way wireless
communications. Currently, wireless communications are limited to half-duplex
or one-way operation. This breakthrough could not only double traffic in the
crowded existing wireless frequencies but could also open up higher millimeter-wave frequencies at 30 GHz and above.

The new technique was recently published in Nature Communications by researchers at Columbia University in
New York. They demonstrate an implementation of a 25-GHz circulator that fits on
a single integrated circuit. This is made possible because the new technique
eliminates the magnets that were needed in previous designs. Instead of
magnets, the device uses a non-reciprocal structure, one with physical
characteristics that differ depending on the direction of flow. As seen in the
figure, the circuit has a pair of transmission lines at the top of the circuit
(the straight section above the dual rings in the center). These lines are
either directly connected or cross-connected, depending on the setting of the
switches at the ends of the transmission lines. If the length is set precisely,
and the switches at one end are 90° out of phase with the other, signals
can travel in one direction but mutually cancel in the other.

Circulator_Columbia_University

Image source: engineering.columbia.edu.

According to the university, the
method “enables loss-free, compact, and extremely broadband non-reciprocal
behavior, theoretically from DC to daylight that can be used to build a wide
range of non-reciprocal components such as isolators, gyrators, and circulators.”
This technique can be used to create a three-port circulator, allowing the
connection of both transmit and receive amplifiers at the same aerial. This
type of connection could support full-duplex operation, “in
which a transmitter and a receiver of a transceiver operate simultaneously on
the same frequency channel, enables doubling of data capacity within existing
bandwidth. Going to the higher mm-wave frequencies, 30GHz and above, opens up
new bandwidth that is not currently in use.”

This approach could be an amazing boon
to the wireless industry. Doubling data capacity could open up a wide range of
new services, those that could reduce data charges for cell phone plans — wouldn’t that be welcome — or could offer increases in communications bandwidth,
perhaps for cloud-based applications — maybe at a premium over current costs, however. Opening up new frequency ranges is exciting, too. Perhaps it would
allow additional services and carriers and increase competition. This could
bring down costs on a wide range of applications. Perhaps 4K class video and
augmented reality will be less costly
than what we have today. If a wide range of high-end frequencies become
available, maybe the “Star Trek”
Holodeck isn’t as far away as one might think, at least as far as the data
communications requirements goes. It could be the artificial intelligence piece that
might be a bit further out.