TECHNOLOGY FOR CHANGE

MEMS Technology to Shrink Mobile Handsets

R. Colin Johnson | Date: 07-01-10 | Comments

Just as micro-electromechanical systems (MEMS) enable accelerometers and gyroscopes to be downsized to chip size, IBM is now employing MEMS technology from WiSpry to consolidate the dozens of radio frequency (RF) components needed for mobile handsets into a single chip, thereby lowering their cost, shrinking their size and extending their battery life.

In the future, mobile handsets could shrink to minuscule sizes by virtue of the same micro-electro-mechanical system (MEMS) technology used to shrink accelerometers and gyroscopes to microchip sizes. Today, dozens of radio frequency (RF) components are needed to send and receive wireless signals from handsets, but, with tunable MEMS chips, the functions served by all those components can be shrunk down to a single RF MEMS chip.

The tunable RF MEMS technology was invented and patented by startup WiSpry (Irvine, Calif.). By enlisting it, IBM Microelectronics has already fabricated sample MEMS chips that consolidate all the various RF components into a single tunable chip designed in standard complementary metal oxide semiconductor (CMOS).

Arrays of digital capacitors allow a radio frequency (RF) circuitry to be tunable to different bands and conditions instead of using dozens of bulky, power-hungry discrete components as is necessary today.

Since, 2007 WiSpry has been showing prototypes of its MEMS chips, which consist of large arrays of capacitors and switches that allow different values of capacitance to be quickly inserted and removed from circuits. This design is more efficient than using multiple components that take up large areas of the printed circuit boards inside today's mobile handsets. And with the popularity of multiband phones that operate in different parts of the world, as well as different bands in the same market�such as 3G and 4G along with peripheral bands like Bluetooth�mobile handsets have become a nightmarish labyrinth of discrete and integrated components, only a few of which are being used at any one time. But by applying tunable RF MEMS components, the same circuitry can be reused for the different bands merely by tuning them with different capacitor values.

In its deal with WiSpry, IBM Microelectronics is retooling its 180-nanometer CMOS process technology to mass-produce the tunable RF MEMS chips. These chips have the potential to downsize mobile handsets, as well as lower their cost and reduce their power consumption. IBM and WiSpry, for instance, estimate that even their first-generation tunable RF MEMS front-end chips for cell phones will increase battery life by 25 percent�and that's just the beginning.

The digital capacitor building block can be used to tune the filters, power amplifiers (PAs) and antenna impedance matching networks, and for general-purpose circuits on a cell phone.

IBM is already shipping samples of its RF MEMS chips, produced to WiSpry's specifications, to major original equipment manufacturers, who plan to begin shipping a new breed of smaller, cheaper, longer-battery-lived cell phones this fall.

IBM and WiSpry also claim that, besides smaller, cheaper and lower power, tunable RF MEMS technology will be able to quickly adapt to changing reception conditions, such as touching the antenna with your finger or moving behind an obstacle, to achieve more consistent connections with more bars and fewer dropped calls. Besides handsets, the tunable RF MEMS chips will also be used in 4G infrastructure equipment and LTE terminals.