Since the advent of wireless technology 60 years ago, magnetic-based circulators have been in principle able to provide two-way communications on the same frequency channel, but they are not widely adopted because of the large size, weight, and cost associated with using magnets and magnetic materials.
Engineers have found a way to dramatically shrink a critical component of cellphones and other wireless devices. A much smaller, more efficient radio wave circulator has the potential to double the useful bandwidth in wireless communications by enabling full-duplex functionality—meaning devices can transmit and receive signals on the same frequency band at the same time.
The researchers did it by ditching the magnets.
“We are changing the paradigm with which isolation and two-way transmission on the same frequency channel can be achieved. We have built a circulator that does not need magnets or magnetic materials,” says Andrea Alu, an associate professor at the Cockrell School of Engineering at the University of Texas at Austin. Freed from a reliance on magnetic effects, the new circulator has a much smaller footprint while also using less expensive and more common materials.
The prototype circulator is 2 centimeters in size—more than 75 times smaller than the wavelength of operation. The circulator may be further scaled down to as small as a few microns, according to the researchers. The design is based on materials widely used in integrated circuits such as gold, copper, and silicon, making it easier to integrate in the circuit boards of modern communication devices.
Lesser Dropped Calls
For telecommunications companies, which pay for licenses to use frequencies allotted by the US Federal Communications Commission, a more efficient use of the limited available bandwidth means significant cost advantages. Additionally, because the design of the circulator is scalable and capable of circuit integration, it can potentially be placed in wireless devices.
The circulator also could benefit other industries that currently use magnetic-based circulators. For instance, circulators used in phased arrays and radar systems for aircraft, ships, and satellites can be extremely heavy and large, so minimizing the size of these systems could provide significant savings.
The Defense Threat Reduction Agency and the Air Force Office of Scientific Research supported the work, which is described in the journal Nature Physics.