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Student Invention May Significantly Extend Mobile Device Battery Life
Posted by
Soulskill
on Fri Dec 19, 2008 07:40 PM
from the wireless-to-wireless dept.
from the wireless-to-wireless dept.
imamac writes with this excerpt from news out of Carleton University:
"Atif Shamim, an electronics PhD student at Carleton University, has built a prototype that extends the battery life of portable gadgets such as the iPhone and BlackBerry, by getting rid of all the wires used to connect the electronic circuits with the antenna. ... The invention involves a packaging technique to connect the antenna with the circuits via a wireless connection between a micro-antenna embedded within the circuits on the chip. 'This has not been tried before — that the circuits are connected to the antenna wirelessly. They've been connected through wires and a bunch of other components. That's where the power gets lost,' Mr. Shamim said."
The story's headline claims the breakthrough can extend battery life by up to 12 times, but that seems to be a misinterpretation of Shamim's claim that his method reduces the power required to operate the antenna by a factor of about 12; 3.3 mW down from 38 mW. The research paper (PDF) is available at the Microwave Journal. imamac adds, "Unlike many of the breakthroughs we read about here and elsewhere, this seems like it has a very high probability of market acceptance and actual implementation."
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Counter-intuitive! (Score:5, Insightful)
Re: (Score:3, Interesting)
I don't think he separating the amplifier from the antenna, but perhaps feeding the amplifier directly attached to the antenna. The loss in signal from source to antenna from the distance of the run has to be made up. This is done by stepping up the output of the amplifier stage.
This configuration isn't uncommon and many microwave systems employ this technique. (Attaching the amplifier nearly directly to the antenna.)
Though I would have to look a bit at the design this is only item I can think of. From near
Impedance Matching technique (Score:3, Informative)
"This configuration isn't uncommon and many microwave systems employ this technique. (Attaching the amplifier nearly directly to the antenna.)"
I agree, it sounds very much like some kind of Impedance Matching technique where the Inductive coupling is direct to the antenna. I'm not so sure that's as patentable as this University is drumming it up to sound. (I guess they hope to earn a lot of money from it, mainly from from phone companies). But Impedance Matching using windings to effectively wireless couple
Re: (Score:3, Interesting)
Re:Counter-intuitive! (Score:5, Interesting)
They also do this in recording studios. It takes far less power and wiring(or can be done via RF or IR) to have each speaker have its own small amplifier than to try to power the whole room with a rack of giant units.
This also would create less interference, believe it or not, since running wires near live electrical components(even the tiny components in a circuit board make a difference - just stick an AM radio near your computer's motherboard) tends to cause interference. This is the other reason recording studios do this. They can run a very heavily shielded or wireless line level signal to each speaker directly. Less power, less clutter, less interference.
Parent
Re:Counter-intuitive! (Score:4, Informative)
Powered speakers are popular because it gives monitor manufacturers a way to make line level crossovers, power amps and speaker drivers work together.
Having control over the specifications of all those components means better fidelity. It is tidier too.
I don't think RF or IR is ever used with studio monitors. They would cause phase alignment problems and a loss of fidelity. Simpler is better, so people use wires. Anyway, aren't we trying to avoid RF transmitters here?
Speaker cables can be shielded too, but people don't bother as any interference would be imperceptible.
Power loss in speaker cables is pretty tiny too. Powered speakers really are all about convenience and potential better fidelity.
Parent
Re:Counter-intuitive! (Score:4, Insightful)
They use wireless just fine with mics and pickups and so on on stage for these reasons all the time. Less cables, less problems, and also if you've ever had to deal with grounding issues, wireless or a line-level signal that's amplified at the source is a huge improvement. I suspect that's the real problem here - too much background RF noise from the components. Rather than brute-forcing it, he decided to find a way to get around this and clean up the signal in the process.
Btw, most pros don't use wired mics any more. Too many issues. Most studios don't use non-powered speakers any more, either. You're right - I haven't found many setups that use IR or wireless(yet), but I can find many professional systems that use S/PDIF, optical, or other non-analog transmission methods.(shoot, most home theater interconnects are now HDMI for exactly these sorts of reasons.
Parent
Re: wired vs wireless audio signals (Score:5, Informative)
Not true.
Wired mics sound better because they lack the companders involved in transmitting the audio signal. Performers like wireless because it's convenient, not because it sounds better. Those concerned with sound quality stick to wired.
Balance signals use common mode rejection to eliminate induced noise. This has been standard practice for years. Recording studios used either balanced wiring, or digital in the form of AES or optical ADAT.
Parent
Re:Counter-intuitive! (Score:4, Interesting)
The problem is that the antenna isn't a major power consumer. It's that the signal path between the circuitry and the antenna is so full of junk on many models due to poor slapped-together designs that the signal must be boosted a lot to communicate with the local cell phone tower. In the old days this wasn't a problem as there weren't major limits on power. Some old Analog units transmitted as much as 10-20W!. Now they have to limit their power to a fraction of that. If the digital signal can't be boosted enough to communicate and it's already at that FCC imposed limit, you're out of luck. No bars. Technically you never actually get "no bars" - you just get too little for the error correction to work any more.
Parent
Re:Counter-intuitive! (Score:4, Interesting)
Now this guy shows us a way to bypass all that and gain the efficiency of removing all those components so that less power is used to get the same amount of radiation out of the antenna.
Parent
Re: (Score:3, Interesting)
How did this get modded insightful?
Its wrong on so many levels.
First, you've confused voltage and amperage.
Second, electricity moving through matter is technically a flow of holes where atoms are missing electrons. You get more resistence when dealing with electricity in this form, fewer atoms equals more resistence since there are few atoms available to make hole swaps with. The skin effect when operating at high frequencies makes the effective resistence of PCB trace higher than direct current but still
Re:Counter-intuitive! (Score:4, Informative)
Parent
Re:Counter-intuitive! (Score:5, Funny)
yes, once we figure out how to overcome the resistance quality of air I envision a new age where we can have wireless like youtube service.
I will call this great thing television.
Parent
Re: (Score:3, Funny)
"Thief! You can't have television unless you pay Comcast $50 a month. You can't just pull television off the air!"
So said my clueless neighbor when I said I get TV for free.
(shaking head)
Re:Counter-intuitive! (Score:5, Informative)
Wires radiate RF like mad unless they're heavily shielded, which is something you really can't do effectively in tight spaces. Of course, testing was done at 5.2GHz, so it will be interesting to see how it works at cellphone frequencies - packaging size might become a factor at lower frequencies.
Parent
Re: (Score:2, Informative)
So you save power versus the conventional design, but you lose range.
Re: (Score:2)
So? You just bump the power up on the new design. 3^2 = 9, so the new design is actually claimed to be 33% more efficient.
Still, that's not zero percent.
Re:Counter-intuitive! (Score:4, Informative)
Except that omnidirectional range is proportional to the cube of the output.
If, as the GP says, you use 1/12 the power of a conventional device with this design, but have 1/3 the range, you need to bump the power to 3^3/12 of a conventional device to get the same range, or 27/12, or more than double.
That doesn't seem like a win to me.
You can't violate the first law of physics:: You don't get sumtin for nuttin.
Parent
How about that inverse-square law? (Score:2, Insightful)
From the research paper: [mwjournal.com]
So you save power versus the conventional design, but you lose range.
To provide the same signal strength at triple the range, you need to broadcast 9 times as much power. To broadcast 9 times as much power with an equally compact transmitter, is it surprising that you need to spend 12 times as much power due to size/efficiency trade-offs?
This doesn't sound like an advance at all.
Re:How about that inverse-square law? (Score:5, Informative)
You are assuming an isotropic emitter, where field strength falls off as 1/r^2. That behavior is invalid for other antennas; for example a dipole's field strength falls off as 1/r (in the far-field approximation). The paper is complicated by the fact that the radiation patterns of the antennas used in this paper are directional and different. The "conventional" chip used a folded dipole with a "boresight radiation pattern", and the "proposed" chip used a custom design with a front-to-back ratio of 10dB.
Table 1 has the numbers:
Module Type / Power Consumption / Gain / Range
Standalone
TX chip / 3.3 mW / -34 dBi / 1 m
TX chip in
conventional
LTCC package / 38 mW / -1 dBi / 75 m
TX chip in
proposed LTCC
package / 3.3 mW / -2.3 dBi / 24 m
Let's do some reckless hand-wavy extrapolation. The difference in power is 38/3.3 = 11.5 = 10.6 dB; if we assume perfect scaling of the new package to 38mW, we'd expect 10.6-2.3=8.3 dBi. This is an improvement of 9.3 dB over the conventional method -- it's almost 10 times as efficient.
This analysis ignores, among other things, the relative directionalities of the antennas. I wonder why they didn't choose a more directional antenna for the "conventional" chip, or used the same sort of antenna in order to do a level comparison.
The other point of comparison is between the "standalone" chip and the "proposed" chip. A 32 dB improvement with no power increase is nothing to sneeze at!
Parent
Re:How about that inverse-square law? (Score:4, Insightful)
I.e. This will not revolutionize the battery life of your iPhone or Blackberry. The losses in the coupling between the integrated PA and the antenna are very small (if we disregard detuning due to human proximity effects. Which is another story, and which is not influenced at all by the design in question.)
The comparison between two different antennas at different powers is not very good science - it is somewhat suprising it got published. (But it is only at a small conference, so it is not that surprising.)
Parent
Re:Counter-intuitive! (Score:5, Funny)
No, you don't get it: wires is how you lose power. Try disconnecting your battery and see how long it lasts then!
In fact I should do my PhD on that.
Parent
Re: (Score:3, Informative)
The summary is misleading.
The paper describes a method of simply and efficiently coupling energy from the transmitter VCO chip to the main antenna, making good use of the R.F. energy that chip provides. It seems that most of the power savings is from avoiding (power used by) an external buffer amplifier by eliminating the amplifier.
That's great if the chip can provide sufficient output power, and if the spectral purity is good enough to comply with F.C.C. or other requirements. I'd expect that most cell p
Re:Counter-intuitive! (Score:4, Interesting)
In the paper three designs are compared:
(1) One with only an antenna on chip. That is, an antenna on the actual chip, with a size of 1x0.5 mm. Draws 3.3 mW, "range" 1m.
("Range" is a very strange measure in RF design...) (2) The same chip but without the on-chip antenna. Instead the power is coupled to an additional PA-amplifier, and an external small folded dipole antenna: Size about 16x10 mm. Draws 38 mW, "Range" 75 m. (3) The same chip withou the PA, with the on-chip antenna coupling to an external patch antenna of size 17x17 mm. Draws 3.3 mW, "Range" 24 m.
In summary: Nice engineering work, but no conclusions can be drawn, as it is very much a case of apples and oranges. (No constant TX power, No constant size, Not very much constant between the designs at all.)
And a classic mobile phone does not use an on-chip antenna at all. So this design will not give any benefit to your iPhone or Blackberry etc.
Parent
Re: (Score:3, Insightful)
This Sounds Like a Great Idea (Score:5, Funny)
Re:This Sounds Like a Great Idea (Score:5, Funny)
Yeah, he'd basically short-range broadcasting his long range broadcast. If you got within several feet of him and used the right equipment, you might be able to listen in on everything he's broadcasting!
Parent
Re:This Sounds Like a Great Idea (Score:5, Funny)
So put a Faraday cage around it?
Parent
Re:This Sounds Like a Great Idea (Score:5, Funny)
Parent
Re:This Sounds Like a Great Idea (Score:5, Interesting)
what are the security ramifications? that a 3rd party might be able to intercept the wireless transmission just like they already can? whether you use this technique or not, you're still going to be broadcasting the signal wirelessly. that's why GSM signals are supposed to be encrypted.
the GSM encryption was broken earlier this year [forbes.com]. the security ramifications of that are far more serious. why would you be worried about someone intercepting this weak wireless signal when attackers can already eavesdrop on your conversation from miles away?
heck, if they're close enough to intercept this signal, then they're already within earshot of you. they wouldn't need to intercept the wireless signal to the antenna. anyone silly enough to do so would look rather conspicuous standing there with a laptop and a directional antenna pointed at your phone.
Parent
Re: (Score:3, Funny)
w....
wh...
who?
**WHOOSH**
I don't get it. (Score:3, Interesting)
What's the win here? He's capacitively coupling the transmitter to its antenna, or what?
-jcr
Re:I don't get it. (Score:5, Informative)
He's using a waveguide coupling to launch the wave to an external hunk of waveguide, rather than running it through pins, wires, PC board traces, etc. The latter are very lossy at cellphone frequencies.
(I'm working on something similar right now and lose virtually all my signal going through about 6" of PC board wiring. B-( )
Parent
Re:I don't get it. (Score:5, Interesting)
From the systems perspective he made a better RF transmitter block. Digging into that block and looking at the RF design level, he simplified the circuitry normally used such as a matching network for the antenna, transmission lines, oscillator (for modulating the information over the carrier frequency), etc into a discrete chip as opposed to multiple printed circuit board components to do that same job.
Beyond that I'd need to study the paper and find more detailed examples of cell phone architecture to have a better idea of the advantages and disadvantages over the legacy design.
Parent
Re:I don't get it. (Score:5, Interesting)
Nevermind that he's apparently ignoring the true cause of a lot of the "lost" power - which is in the various bandlimiting filters that any real cellphone pretty much can't do without. It's tough to get a good multiband filter that doesn't have 1 to 2 dB insertion loss. The apertures are also geometric, so you are automatically sensitive to odd-order harmonics in both directions.
And I wonder how his aperture's impedance matches the amplifier out of band? From what I've seen in bleeding-edge RF architectures over the last 20 years or so, it's far easier to make a poor oscillator than a good amplifier, with any given set of components.
Parent
But what % of battery use does it represent? (Score:5, Interesting)
I mean my phone lasts for days if i don't use it and many hours if i'm just talking. The vast majority of power seems to be used when I'm watching video, playing games, or browsing the web. My guess would be this is more CPU related.
So even if it saves 10x in the transmit/receive it still might only be a 2x overall savings or less. I suppose it depends on usage patterns.
Re:But what % of battery use does it represent? (Score:5, Funny)
Yes. His approach would only help people who use their phones primarily to *gasp* make phone calls. Blasphemy?
Parent
The radio is a non-trivial part (Score:2)
Goes double for WiFi, which is an extremely chatty protocol and thus sucks power. Could make WiFi much more usable in smartphones. Right now, if you play with WiFi much, you'll find that your battery gets drained fast as compared to EVDO or the like.
Less range by 3x; less power by 12x (Score:2, Informative)
Last line of the pdf:
The conventional LTCC package provides 3 times more range than the proposed design but consumes 12 times more power.
I am no chip designer..... (Score:2)
(only a software engineer) ... but when you tell me that replacing copper wires with a (wireless) transmitter and receiver helps save power: well I am a non-believer. Sorry. Just does not cut it whatever the headlines say. How about quality ?
Re:I am no chip designer..... (Score:5, Interesting)
For once, something that I'm actually qualified to post on!
I was a Weapons system depot level tech in the navy, doing lots of work with waveguides, radar, etc. I went on to work in the private sector, doing among other things antenna design at Nortel.
I can't help but say this is a bunch of shit. It is ALWAYS more energy-expensive to do wireless, it's just the way things are.
If it is just the journalist making a mistake, I can see some possible advances in energy conservation using a waveguide, or even a virtual waveguide; anything else would only start to be possible if you enter the realm of high energy physics.
Unless this guy's name is Tesla, and/or they have developed a completely new principle...
Parent
Re:I am no chip designer..... (Score:5, Interesting)
I'm not as qualified as paganizer, as I usually work at much higher frequencies (mmwave). However, losses from the PA to the antenna are typically pretty low. The claim of 12x improvement imply the current interconnects are at best 8% efficient (utter BS!).
From the PA to the radiated signal you typically have:
1. On PA losses because of their design. For example they typically have at least 3 different output stages to span from just a few milli-watts (single HBT cell), up to full power (hundreds of milli-watts, hundreds of HBT cells). The parasitics of driving the unused cells at less than full power operation creates small losses, but I don't know a hard number for this.
2. Baluns/impedance transforms. PA's are typically class B operation with a load line that is just a few Ohms (3V Vcc, and hundreds of mA of DC power, so the RF loadline is pretty steep). Solutions are matching structures, or a push-pull architecture through a balun to transform up to 50 Ohms. These usually account for 0.5-1 dB of loss (10-20%) of power. The invention ignores this part of a cell phones design.
3. Multi-band switch. Missing in this article is that most phones are designed to operate on at least 2, often 3 frequency bands. Several PA's are used, each designed to cover only one band. A GaAs phemt switch is usually used to switch between the two or more PA die. The invention does not address this aspect of cell phone design. These chips are either integrated in with the PA chip (separate die in the same carrier), or in some cases done in a different chip.
4. Small line loss from the PA chip to the antenna do have modest loss, usually just a few tenths of a dB (few percent). The article addresses this aspect of things.
5. The antenna is a clusterfuck of design hassles, as it is often dual, or tri-band in nature. A lot of compromises go on with the antenna. Making it have multiple resonances to cover the bands is hard. Making it small is hard. Making it work with the crappy ground plane, user's hand and head, and technicolor plastic case is damn hard. The article glosses over all this, and talks about a single narrow band antenna scenario.
Parent
operate the ***ANTENNA*** (Score:2)
If the circuite powering the antenna was the greatest consumer of power in the device, this would result in a significant improvement to the end-user. However, it's all the other bits in the device which eat thousands of times more power -- the CPU, the display, the speakers, etc.
Interesting discovery, but the real-world savings will be few.
Kind of a misnomer (Score:4, Interesting)
I don't think this will "significantly extend" mobile device battery life, As other people have pointed out, something that could practically save maybe 10mW of battery power during transmit operation is interesting but not really all that dramatic. On the other hand, the author doesn't appear to make the claim that it will or won't significantly extend battery life. That may be a slashdottism :)
If I understood the abstract right, the gist of this is that he designed a transmit module with a small internal loop antenna, so that a larger transmit antenna could be inductively coupled instead of electrically driven. This means that all of the bias and driver circuitry internal to the transmit chip and also all of the bias and transmit circuitry external to the chip could be done away with. He coupled an antenna to the outside of a microchip to utilized what would essentially be 'waste' magnetic field in a conventional transmitter.
I would also bet that the big boys like Qualcomm probably do something similar already inside of their cell-phone modules. I would imagine that an approach like this eliminates much of the general purpose interfacing that needs to be done between some arbitrary microwave transmit module and some other arbitrary antenna, but things like cellphone transmitter chipsets are so tightly integrated that I bet they already implement something similar.
Student? (Score:5, Insightful)
Ph.d candidate... is factual and much less sensationalized.
Re: (Score:2, Informative)
Definitely bad journalism. The culprit isn't wire resistance, it's reactance. The impedance mismatch at the junctions from amplifier to circuit board to connector to cable to antenna all create reflections and thus standing waves [wikipedia.org]. The power that goes into those standing waves is reflected back into the amplifier, where it is dissipated as heat. The result is that you need (in his example) a 38mW amplifier in order to get 3.3mW of radiated power out of the antenna.
What his invention does is create a near
Re:What? (Score:5, Informative)
Oh my god. Please not another "informative" post. I really wish you people would stop commenting on these articles when you clearly have no clue what you are talking about. The reflected power (if it happens to exist in this case...which it doesn't because these transmitters are designed quite well and usually include a circulator or isolator at the output of the amplifier to ensure an excellent match) does not go back into the amplifier, because if it did the amplifier would not work as it was designed and would either oscillate or produce extremely poor waveform quality at the output.
Now, if you can bypass the circulator/isolator I mentioned above (which is what I gather they are trying to do in this article) then that is one less place power can be lost on the way to the antenna.
Parent
Re:What? (Score:4, Informative)
The article is crap. The paper, however, makes sense. Read it.
Parent
Re: (Score:3, Funny)
Same way you tune a fish.
Re: (Score:3, Funny)
start eating the pringles out of it, that reduces interference with the other components inside. That is a good start IMO