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Harmonic Devices, winners of the UC Berkeley Business Plan Competition. From left to right: Justin Black, John Hwang, Gianluca Piazza, Phil Stephanou, and Kenny Miller.

For two years, UC Berkeley Engineering graduate students Gianluca Piazza, Phil Stephanou, and Justin Black were developing an atomic clock far tinier and cheaper than today's technology. They hoped that in the future, their sugarcube-sized device, accurate down to ten quandrillionths of a second per day, might improve data encryption, speed up computer networking, and boost the accuracy of the Global Positioning System (GPS). Then opportunity rang. The students realized that one of their clock components also had the potential to revolutionize cellular telephone electronics. In the last few months, their idea has brought them gold in three major business plan competitions. Now it's time to start a company.

"There are probably a few hundred thousand atomic clocks that our technology could replace," says Piazza, who hopes to earn his PhD in electrical engineering later this year. "Compare that to 700 million cell phones sold last year. The potential impact is much greater."

A scanning electron micrograph (SEM) showing a circular ring resonator with an inner radius of just 90 microns, less than the diameter of a human hair. (courtesy the researchers)

Already, mobile phones are bursting with features, from cameras to video playback capabilities. At the same time, various cellular networks around the globe operate on different frequencies, or bands, yet we want our phones to work wherever we are, preferably with Internet connectivity . The problem is that as new features emerge, and our demand grows for tri-band and even quad-band phones, the number of components that must be packed into each handset also increases. The students' invention enables manufacturers to add more functionality to phones while keeping the price down and the form factor svelt.

Wireless radios depend on crystal oscillator clocks to provide an accurate timing pulse and frequency reference. Meanwhile, two types of filters ensure that only the intended bit of the scarce frequency spectrum is used for each call. Unfortunately, these types of components are usually bulky, power-hungry, and expensive. While integrated circuits are fabricated on silicon, the quartz crystal and filter are built on more exotic materials. This means they can't be manufactured as part of the main integrated circuit that handles a phone's wireless tasks.

"Right now, you have to package these things separately and solder them on to the circuit board," says Stephanou, a mechanical engineering PhD candidate. "Our technology is compatible with the same fabrication techniques used to make the RF circuits, so you can just build them on the silicon right next to the phone electronics."

An array of circular- and square-shaped MEMS resonators function as filters for a wireless transceiver. (courtesy the researchers)

The main ingredient in the new device is a tiny resonator, the heart of the atomic clock that the students developed with professor Albert Pisano, chair of the Department of Mechanical Engineering and a director of the Berkeley Sensor and Actuator Center (BSAC). Pisano is Piazza and Stephanou's faculty adviser while Black conducts his resonator research with BSAC co-director, electrical engineering and computer sciences professor Richard White. The MEMS (micro-electromechanical Systems) resonator is like a microscopic guitar string that vibrates only at a specific frequency when it's plucked. That frequency can be used as a reference by both the clock and the filters.

Unlike other MEMS resonators that are long and narrow, the students' device is shaped like a donut with a radius thinner than a human hair. It's fashioned from aluminum nitride, a material that resonates in the presence of an electric field. The resonant frequency is determined by the width of the ring.

"Rather than a linear resonator, the ring structure provides a larger area so the structure can vibrate radially and that improves the performance," Stephanou says.

Another benefit is that several resonators of various sizes can be fabricated onto a single integrated circuit. That way, a phone can operate on multiple bands without the additional cost or space requirements of multiple off-chip filters.

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Late last year, the three engineers teamed up with Berkeley MBA students Kenny Miller and John Hwang to explore the business potential of their idea. Patents were filed and a company, Harmonic Devices, was born. This spring, their collaborative business plan won first place in the Berkeley Nanotechnology Club's Nano Opportunity Challenge, the University of San Francisco 's International Business Plan Competition, and the UC Berkeley Business Plan Competition. As the students work to complete their PhDs, Harmonic Devices is actively seeking venture capital to take their device to market.

"Business is a protocol that allows you to take what you've learned in the lab and apply it in society," Stephanou says. "Otherwise, these kinds of things would remain research projects and academic papers. The only way we're going to get this into people's cell phones is to make a business case for it."

"Good Timing for Nanoscale Atomic Clocks" by David Pescovitz (Lab Notes, September 2002)

"Harmonic Devices Takes Top Prize at the UC Berkeley Business Plan Comptetition"

"Graduate students win international business plan competition, start new company" by Rachel Jackson (Engineering News, April 4, 2005)

Berkeley Sensor and Actuator Center

UC Berkeley Microfabrication Laboratory

Berkeley Nanotechnology Club

UC Berkeley Business Plan Competition

USF International Business Plan Competition

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