MIT Research Tweaks Smartphone Amplifier Voltage To Gain Battery Life 47
hypnosec writes "Two MIT electrical engineering professors, Joel Dawson and David Perreault, have claimed that they have cracked the age old efficiency problem related to the power amplifier in smartphones by designing a new amplifier that consumes just half the power as compared to their current counterparts. Current transistor-based power amplifiers consume power in two modes – 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 mode. The problem here is that if the power is kept very low when in standby mode, because of sudden jumps from low-power standby mode to high-power output mode, signals get distorted. This is why current technologies waste a lot of electricity as standby power levels are kept at a relatively higher level to avoid distortion. The new technology, dubbed asymmetric multilevel outphasing, is basically a blazingly fast electronic gearbox that would select the best possible voltage to send across to the transistors that would minimize power consumption."
I hope they've done the needful... (Score:4, Interesting)
...and filed a patent for the implementation or call it execution....otherwise some clever company, that is better known for suing others in the industry,; that's had one of its famous patents invalidated recently, will file...and sue.
hybrid A/theta modulator (Score:5, Interesting)
One way to do high efficiency is to do separate phase and amplitude modulation, the so called A-theta modulator. you get your amplitude control by adjusting the PA voltage _continuosly_ and do your phase modulation with an IQ modulator.
For wide bandwidth modulation formats this is a bit of a pain since you need a very wideband, high current, power supply. so they are doing an A/theta modulator but trying to simplify the bias control on the PA to avoid that.
What I'm not clear on is why they are doing this when they have a predistortion loop anyway. a pure predistortion loop should be able to achieve very similar results without any need for the PA bias adjust. you can also do it with 1 PA instead of two.
maybe it simplifies the PD loop substantially, I can't tell yet from the paper, but it trades this off against needing two PAs and PA bias control. And that PA bias control is a bit of a headache two, because you can't just stick a switch in there. The selectable bias levels have to come from a switching power supply which switches between different output voltages. doing this is also non-trivial.
I don't know, looks like somebody's thesis to me. Doesn't look like it's particular practical.
Also, first rule of looking at schemes like this. How much of that power they saved is being used in the more complicated digital circuitry. That's the reason you don't see PD loops in cell phones. It's a wash, you spend so much power analyzing the signal to do PD that you burn up the savings . Now if you have a 10W transmitter, PD makes lots of sense.