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MIT researchers double battery life

Sorting out the amp in a mobile phone

Two MIT researchers claimed that they have doubled the life of a mobile phone battery by tweaking an efficiency problem related to the power amplifier.

The professors Joel Dawson and David Perreault claim that power amplifiers are to blame for much of the draining of a mobile phone and the amp chips waste as much as 65 per cent of their energy. They have formed a startup called Eta Devices which will flog gear that they claim to have solved this problem.

The technology is currently being tested in labs. They think that if it is adopted base station energy usage will be down by 50 per cent and once a chip-scale version of the technology is developed and commercialised, smartphones will have double the battery life.
At the moment transistor based power amplifiers consume power in standby and output signal mode.  The only way to reduce power consumption and increase battery life is to use the least possible power when in standby.

But if the power is kept too low when in standby mode the sudden introduction of power creates a signal spike and the sound is distorted. This means that standby power levels are kept at a relatively higher level to avoid distortion, but this also costs a lot of electricity. Dawson said that the problem gets worse with high data rate communication,  because you need more standby power than signal power.

The pair's technology is called asymmetric multilevel outphasing which works like an electronic gearbox that would select the best possible voltage to send across the transistors that would minimize power consumption. It can do this at about 20 million times per second.

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