'stretchability' 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. The team built a graphene NEMS whose frequency was about 100 megahertz, 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.
"This device is by far the smallest system that can create such FM signals," says Hone.
While graphene NEMS will not be used to replace conventional radio transmitters, they have many applications in wireless signal processing. Explains Shepard, "Due to the continuous shrinking of electrical circuits known as 'Moore's Law', today's cell phones have more computing power than systems that used to occupy entire rooms. However, some types of devices, particularly those involved in creating and processing radio-frequency signals, are much harder to miniaturize. These 'off-chip' components take up a lot of space and electrical power. In addition, most of these components cannot be easily tuned in frequency, requiring multiple copies to cover the range of frequencies used for wireless communication."
Graphene NEMS can address both problems: they 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.
"There is a long way to go toward actual applications in this area," notes Hone, "but this work is an important first step. We are excited to have demonstrated successfully how this wonder material can be used to achieve a practical technologiPage: 1 2 3 Related biology technology :1
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