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New Chip Promises Longer Battery Life
Roland Piquepaille writes "It always happens when you need it the most: the battery of your cellphone just died. But now, researchers of the University of Rochester have developed a wireless chip that needs ten times less power than current designs. The new chip relies on a technology named injection locked frequency divider (ILFD) which dramatically reduces the time needed to check for transmission frequencies which are performed several billion times per second by your current phone. The new chip uses five transistors and can perform divisions by 3 instead of only 2 by previous circuits, allowing a perfect communication between two phones communicating at 2.0001 and 2.0002 gigahertz respectively."
Dude: Hui Wu invented this new chip that saves loads of power.
Bloke: Who?
Dude: Yes
Bloke: so who invented this chip.
Dude: Hui did.
Bloke: Thats what I'm asking you.
Dude: Yer I know, Hui did.
Bloke: Quit it and tell me who invented the chip.
Dude: Im not joking, Hui did.
liqbase
The Problem is not that the PLL uses lots of energy, the problem is that digital circuitry, which the PLL feeds, uses power that is proportional to the frequency at which the PLL drives it. If you have a digital circuit at 2 GHz, it will use one tenth of the power of a circuit which runs at 20 GHz. This is important because traditional digital circuits which communicate with each other on specific frequencies, do so by running a clock speed of at least 10 times the communication frequency, and then using a microporcessor to count up clock pulses in order to exactly equal the right frequency. If you are running at 10x the communication frequency, then you need to count ten clock pulses for each communication signal cycle. If you need greater accuracy, then you need more clock pulses per communication cycle to get that accuracy. Thus, your digital circuits are in effect running at much higher clock frequencies than are necesary to actually achieve the communication. This is why your little 2 watt tx/rx chip actually consumes closer to 20 watts when it is communicatng actively.
What these researchers have done is found a way to adjust the frequency of the digital circuitry to exactly match the communication frequency, so instead of counting pulses, we can safely assume that 1 digital signal cycle = 1 communication cycle. This is just as good as clock pulse counting when it comes to processing digital communication signals, but up until now there was no way to adjust the source frequency with any real accuracy, so you had to run the source frequency very fast and count up pulses to get accuracy. Now, we no longer have to count, we just use one pulse / cycle, and were all set.
To explain in a slightly different way, we'll use the analogy of trying to accurately count a mountain of pennies. The easiest way to do so, is to weigh the whole pile, and then divde by the average weight of a single penny, and you get the total number of pennies. The question is how you get the "average weight" of a single penny. If you weigh just one penny, and use that as the average, then you have some total inaccuracy X. If you instead weigh 10 pennies and divde the weight by 10, the inaccuracy is much less: roughly X/10. This is how the old method of PLL circuit design worked. The greater the frequency, the more pennies you used to find the average weight, and so the greater the accuracy you could get in finding out the total number of pennies in the whole pile, or the exact frequency.
The new method described in the Article is roughly analagous to modifying all of your pennies to ensure that the variation in the weights of the pennies is much lower, so you can rely on just one penny to provide you with the precision needed to determine the total number in the pile.
I hope this cleared up some of the confusion.
-=Geoskd
I wish I had a good sig, but all the good ones are copyrighted
Bender: "Ahhh, what an awful dream. Ones and zeroes everywhere... and I thought I saw a two!"
Fry: "It was just a dream, Bender. There's no such thing as two."
E pluribus unum
Actually, I'm still a little confused. Could you try an analogy using cars instead? Thanks.
Bonsai Kitten: TNG
Out of curiousity, why have we not yet figured out how to wirelessly power devices?
Short answer: We already have, it is just so inefficient that nobody uses it. (in fact it was invented over 100 years ago!)
Long answer: Electromagnetic waves radiate outwards. Either you have a simple non-directional antenna that radiates in all directions at the same time (in a sphere basically) and you lose power REALLY fast, or you have a directional antenna that radiates power in a cone at a target destination.
The omni-directional radiators suck so much that they are absolutely useless. Inverse square means 1/(x^2). Basically (and this is crappy math but gets the point across) if you have 10 watts at 1 feet, you would have 10*(1/(2^2)) = 2.5 watts at 2 feet. At 3 feet you would have 10*(1/9) = 1.11 watts. Please ignore that you would use meters instead of feet and that all my units are all messed up in various other ways as well. The point is that your power drops off REALLY fast.
So what about those directional antennas?
Well, you have to find some way to really accurately track someone's cell phone position, and have a world-wide array of directional antennas so that you can beam power to them no matter where they are at.
Oh and remember to keep those power levels low, else you will fry anything that gets in the way.
People worry about cell phones causing cancer as it is, directional power beamed at your head WOULD cause some serious issues!
Wireless power is possible, just not feasible!
Need help treating your acne? Come here!
To explain in a slightly different way, we'll use the analogy of trying to accurately count a mountain of cars. The easiest way to do so, is to weigh the whole pile, and then divde by the average weight of a single car, and you get the total number of cars. The question is how you get the "average weight" of a single car. If you weigh just one car, and use that as the average, then you have some total inaccuracy X. If you instead weigh 10 cars and divde the weight by 10, the inaccuracy is much less: roughly X/10. This is how the old method of PLL circuit design worked. The greater the frequency, the more cars you used to find the average weight, and so the greater the accuracy you could get in finding out the total number of cars in the whole pile, or the exact frequency. The new method described in the Article is roughly analagous to modifying all of your cars to ensure that the variation in the weights of the cars is much lower, so you can rely on just one car to provide you with the precision needed to determine the total number in the pile.
My 0.02 cents
Make a 9volt USB battery charger
p ?pe=CBHJGEGQ_+mobile+phone+wind+up+charger&cid=880
d -powered-phone-charger.html
http://www.hackaday.com/entry/1234000520028239/
Or a WIND UP charger
http://www.edirectory.co.uk/pf/pages/moreinfoa.as
or a WIND TURBINE PHONE CHARGER
http://www.bytesurgery.com/gearedup/2006/02/a-win
Liberty freedom are no1, not dicks in suits.
I don't post here very often, but this time I couldn't handle this. (Maybe I should drink less coffee). There was probably some paper at that uni, talking about an incremental improvement in frequency divider design. Ok, cool ... we may or may not see in in a PLL chip in a few years. But the news release (TFA) and RP's writeup are rubbish. Actually, after a bit of Googling, it's all over the net. Next thing I expect, my PHB will ask me to change my totaly unrelated design to use ILFD. My signature notwithstanding, I'll try to pick out some of the c***p, and put some actual information in. BTW, I design 3G mobile terminal circuitry full time. And yes, I am an arrogant SOB. That doesn't make me wrong.
"...But now, researchers of the University of Rochester have developed a wireless chip that needs ten times less power [GC] than current designs."
So far so good.
The new chip relies on a technology named injection locked frequency divider (ILFD) which dramatically reduces the time needed to check for transmission frequencies which are performed several billion times per second by your current phone.
This statement is wrong 2 times. First of all, the time needed to check for transmission frequencies depends on PLL settling time. Nothing to do with divider technology. Even broader scope, it is a rare occurence in 3G that the phone needs to change RF frequency. It's WCDMA, so all cells from a given operator transmit on the same channel. Secondly, tthe checking for transmission does NOT occur "several billion times per second". The RF carrier frequency is several billion cycles per second (ie several GHz). But the carrier frequency is changed on every 10ms roughly, even when it needs to happen. That's 100 times per second. GSM is different, as it does frequency hopping normally, but that doesn't change the point: nothing to do with divider technology.
The new chip uses five transistors and can perform divisions by 3 instead of only 2 by previous circuits
OK, agreed. Anyway, who gives a f**k. A modern PLL chip has a programmable divider, settable from 3 to several thousand. Yes, 3, because it is different technology.
That's not how mobile phones work. Mobiles establish connection with the cell (base station), then remain frequency locked to it, to compensate for temperature dependant frequency variation of their reference reference crystal oscillators - and Doppler shift, if they are moving. A "perfect" communication hardly ever depends on this. And frequency locking does not happen via changing PLL settings in this case anyway - too coarse steps, so other techniques are used.
Anyway, as other people posted already, the frequency synthesizer is not significant contributor to mobile terminal power consumption. Even old PLL chips only use a few milliamps
The ILFD technology seems to be good for building efficient frequency dividers at higher microwave frequencies. That will probably not affect current mobile phones anyway, because all the current systems work around 1-2GHz. Higher up, it's difficult to achieve coverage. Again, other people already pointed this out.
If you want real news in this area, go to sites like this, or this. Slashdot's editorial quality has degraded in the last few years so much that I am thinking about deleting it from my bookmarks.
[/rant]"Argue with idiots, and you become an idiot." -- Paul Graham