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MEMs RF front-end filters needed

Posted: 11 Feb 2005 ?? ?Print Version ?Bookmark and Share

Keywords:microelectromechanical systems? mems? rf? radio frequency? front-end filters?

The microelectromechanical systems industry has huge opportunities in the market for radio frequency front-end filters, panelists said here during the International Solid-State Circuits Conference.

However, MEMS proponents have yet to convince most customers that cost targets can be reached for nonmilitary applications, several of the experts agreed.

Clark Nguyen, a University of Michigan MEMS pioneer who also administers a Defense Advanced Research Projects Agency (Darpa) MEMS program, said the technology has a future in the filters required in handsets to select the proper RF channel, and for frequency generation. MEMS-based solutions have quality (Q) factors that exceed 10,000, well beyond conventional ceramic filters.

"We have to look upon MEMS not just as replacing ceramic filters, but as solutions with Q factors that are so robust that they represent a revolution, not an evolution," Nguyen said.

With higher-quality channel selection filters, the task facing the demodulation electronics could be greatly simplified, he added.

Bill Krenik, a wireless research and development manager at Texas Instruments Inc., said wireless handsets must be able to support an increasing number of wireless standards, from Wi-Fi to wideband CDMA and beyond. "We have a lot of bands to support, and to do that we might need five LNAs (low noise amplifiers). RF front-end filtering is a real problem where MEMS could help the industry," Krenik said.

However, MEMS devices are not cheap, making insertion into the commercial handset market a challenge. Still, lucrative opportunities are emerging in the software-defined radios being adopted by the U.S. military, and in phased-array radars and satellites, said Dan Hyman, founder of XCom Wireless, which makes subsystems based on MEMS relays and varactors. The panelists differed on the challenges faced by stiction, the tendency of two metal-based MEMS materials to stick together. Bob Peurs, a MEMS researcher at Katholieke University, said stiction, material wear-out and packaging challenges remain. Hyman said the industry has figured out solutions to stiction, partly by reducing the amount of charge pumped through beams in the MEMS structures.

- David Lammers

EE Times

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