Graphene Mixer for Microwaves

Graphene, a single atom-thick sheet of graphite, is turning out to be useful in a wide range of products, so perhaps I shouldn't be surprised that Chalmers University researchers have used it to create a novel sub-harmonic graphene FET mixer for use at microwave frequencies. They see the device being used at terahertz frequencies for radar, radio astronomy, process monitoring and environmental monitoring.

"The ability in graphene to switch between hole or electron carrier transport via the field effect enables a unique niche for RF IC applications" the University said in a press release. "Thanks to this symmetrical electrical characteristic, the researchers at Chalmers have managed to build the G-FET sub-harmonic resistive mixer using only one transistor. Hence, no extra feeding circuits are required, which makes the mixer circuit more compact as opposed to conventional mixers."

The release further noted that a mixer constructed with this technology would require less chip wafer area and could provide the potential to build sensor arrays that could be useful in the imaging of millimeter and sub-millimeter waves.

Jan Stake, professor of the research team, sees room for improvement. "The performance of the mixer can be improved by further optimizing the circuit, as well as fabricating a G-FET device with a higher on-off current ratio. Using a G-FET in this new topology enables us to extend its operation to higher frequencies, thereby exploiting the exceptional properties of graphene. This paves the way for future technologies operating at extremely high frequencies."

While the Chalmers research focused on terahertz frequencies, I wonder if G-FET devices will eventually compete with gallium arsenide (GaAs) and silicon based devices at Ka-band and lower microwave frequencies.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.