World’s Smallest FM Radio Transmitter

World’s smallest FM radio transmitter was designed by a team of Columbia Engineering researchers and published their study online on November 17, 2013 in Nature Nanotechnology, this team was led by Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard, it is possible by taking the advantage of graphene’s special properties (mechanical strength and electrical conduction) and created a nano-mechanical system that can create FM signals.

(Placing a sheet of atomically-thin graphene into a feedback circuit causes spontaneous self-oscillation that can be tuned to create frequency modulated (FM) signals)

Graphene’s mechanical ‘stretchability’ is used to tune the output frequency of their custom oscillator, creating a nanomechanical version of an electronic component known as a voltage controlled oscillator (VCO). With a VCO, explains Hone, it is easy to generate a frequency-modulated (FM) signal, exactly what is used for FM radio broadcasting. A frequency about 100 MHz was built a team using graphene nanoelectromechanical systems (NEMS), which lies right in the middle of the FM radio band (87.7 to 108 MHz). They used low-frequency musical signals (both pure tones and songs from an iPhone) to modulate the 100 MHz carrier signal from the graphene, and then retrieved the musical signals again using an ordinary FM radio receiver.

Hone says. "In advancing wireless signal processing and designing ultrathin, efficient cell phones. Our devices are much smaller than any other sources of radio signals, and can be put on the same chip that’s used for data processing.” he also added “This work is significant in that it demonstrates an application of graphene that cannot be achieved using conventional materials,” 

Graphene NEMS are very compact and easily integrated with other types of electronics, and their frequency can be tuned over a wide range because of graphene’s tremendous mechanical strength. Now both working to improve the performance of the graphene oscillators by lower noise in signals. At the same time, they are also trying to demonstrate integration of graphene NEMS with silicon integrated circuits, making the oscillator design even more compact.

Source: http://engineering.columbia.edu/