New device counters problems of 'dropped calls and slower downloads'

Purdue University researchers have created a tiny mechanical device, an electrostatically actuated nanoresonator, that could help cell phone users avoid the nuisance of dropped calls and slow downloads.

It is designed to ease congestion over the airwaves to improve the performance of cell phones and other portable devices.

"There is not enough radio spectrum to account for everybody's handheld portable device," said Jeffrey Rhoads, an associate professor of mechanical engineering at Purdue University.

The overcrowding results in dropped calls, busy signals, degraded call quality and slower downloads. To counter the problem, industry is trying to build systems that operate with more sharply defined channels so that more of them can fit within the available bandwidth.

"To do that you need more precise filters for cell phones and other radio devices, systems that reject noise and allow signals only near a given frequency to pass," said Saeed Mohammadi, an associate professor of electrical and computer engineering who is working with Rhoads, doctoral student Hossein Pajouhi and other researchers.

Nanoelectromechanical resonators contain a tiny beam of silicon that vibrates when voltage is applied. Researchers have shown that the new devices are produced with a nearly 100 percent yield, meaning nearly all of the devices created on silicon wafers were found to function properly.

"We are not inventing a new technology, we are making them using a process that's amenable to large-scale fabrication, which overcomes one of the biggest obstacles to the widespread commercial use of these devices," Rhoads said.

In addition to their use as future cell phone filters, such nanoresonators also could be used for advanced chemical and biological sensors in medical and homeland-defense applications and possibly as components in computers and electronics.

The devices are created using silicon-on-insulator, or SOI, fabrication - the same method used by industry to manufacture other electronic devices. The resonators can be readily integrated into electronic circuits and systems because SOI is compatible with complementary metal–oxide–semiconductor technology, or CMOS, another mainstay of electronics manufacturing used to manufacture computer chips.

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