Student Invention May Significantly Extend Mobile Device Battery Life 160
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."
Comment removed (Score:3, Interesting)
Re:Counter-intuitive! (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 nearly every phone I have busted the antenna is usually separated quite a bit from the rest of the components.
Re:Counter-intuitive! (Score:3, Interesting)
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:Counter-intuitive! (Score:1, 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.
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...
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.
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.
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.
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.
Re:Less range by 3x; less power by 12x (Score:2, Interesting)
Also, this only deals with the transmit side of things. In a phone, the antenna is also used to receive signals. Normally a T/R switch is used which has loss. This paper does not include any mechanism for receive circuitry. Given that the oscillator is really part of the antenna, would make incorporating a receiver extremely difficult.
A further concern is the transmit VCO is very tightly coupled to the antenna. The author of the paper cites this as an advantage. I wonder what would happen if I hold this antenna near some metal? It would detune the antenna and therefore cause the VCO to detune. This is called Load-pull and is always undesirable.
This scheme has no harmonic filter whatsoever. The pesky FCC makes you test this. Ironically, the Dept of Industry in Canada is even worse in this regard than the FCC. I doubt that this would pass those requirements.
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.
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.
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.
Re:Counter-intuitive! (Score:2, Interesting)
Powered speakers exist because it reduces the cabling between the amp and speaker to a minimum thereby reducing the resistance to a minimum and subsequently maximising the damping factor.
Whilst active monitors are common in smaller control rooms, particularly broadcast/post production and smaller music studios you will still find passive monitor/discreet amplifier configurations in larger control rooms particularly music studios.
Only a masochist or someone who mistakenly thinks it's easier to screen out interference from speaker cables than line or worse mic/instrument level ones, would use wireless speakers in a 'recording' studio. I have known studios threatened with lawsuits because customers have been 'blasted' with either noise or feedback so having high powered monitors that can be crashed by some talent talking to her agent on a cellphone would be playing russian roulette and I have yet to find them used in any commercial facility ( and trust me with 20yrs in the studio systems business I've been in a few ! ). I would certainly NEVER use them in a design and would probably refuse to be involved in a design that did ( it's never happened yet ).
Despite their original reason for being, active monitors are these days used for other reasons including convenience as it's a lot easier to put small actives in a voiceover booth or OB truck than find space for amps and cables but I have never known them be used for reasons of power usage or interference which is fortunate as I would find it difficult to supress my sniggers.
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.
Re:Counter-intuitive! (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 fair lower than open air. The very thought that air is more conductive than a copper trace on the PCB is silly.
The key to this guys idea is that you get rid of not just the wire, but OTHER COMPONENTS such as filters that deal with other issues related to the length of the trace.
Its not the PCB trace thats eating the power, its the filter caps, coils, connectors and other such things that add resistence to the system and rob power.
For future reference just because you read the wikipedia article doesn't mean you know what you're talking about, especially in cases where you clearly didn't understand the wikipedia article, potential difference (voltage), skin effect, or electrical resistence in general.