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October 31, 2012

Smartphones that Use Half the Power

Technology Review - Powering cellular base stations around the world will cost $36 billion this year—chewing through nearly 1 percent of all global electricity production. Much of this is wasted by a grossly inefficient piece of hardware: the power amplifier, a gadget that turns electricity into radio signals.

The versions of amplifiers within smartphones suffer similar problems. If you’ve noticed your phone getting warm and rapidly draining the battery when streaming video or sending large files, blame the power amplifiers. As with the versions in base stations, these chips waste more than 65 percent of their energy—and that’s why you sometimes need to charge your phone twice a day.

An MIT spinout company called Eta Devices say they have cracked the efficiency problem with a new amplifier design.



It’s currently a lab-bench technology, but if it proves itself in commercialization, which is expected to start in 2013—first targeting LTE base stations—the technology could slash base station energy use by half. Likewise, a chip-scale version of the technology, still in development, could double the battery life of smartphones.

“There really has been no significant advance in this area for years,” says Vanu Bose, founder of Vanu, a wireless technology startup. “If you get 30 to 35 percent efficiency with today’s amplifiers, you are doing really well. But they can more than double that.”

Power amplifiers use transistors that consume power in two basic modes: standby mode and output signal mode when sending out pulses of digital data. The only way to improve their efficiency is to use the lowest amount of standby power possible. But making sudden jumps from low-power standby mode to high-power output mode tends to distort signals, so existing technologies keep standby power levels high, wasting electricity.

The new advance is essentially a blazingly fast electronic gearbox. It chooses among different voltages that can be sent across the transistor, and selects the one that minimizes power consumption, and it does this as many as 20 million times per second. The company calls the technology asymmetric multilevel outphasing.

Eta Devices, funded by $6 million from Ray Stata, cofounder of Analog Devices, and his venture firm, Stata Venture Partners, is expected to formally launch its product in February at Mobile World Congress in Barcelona, Spain. The initial market will be in the developing world, where 640,000 diesel-powered generators are used to power base stations, chewing through $15 billion worth of fuel per year.

But the company is aiming at the massive smartphone market. It hopes that its work on a smartphone chip will ultimately lead to a single power amplifier that can handle all of the different modes and frequencies used by the various global standards, such as CDMA, GSM, and 4G/LTE. (Inside an iPhone 5, for example, there are currently five such chips.)


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