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Student Invention May Significantly Extend Mobile Device Battery Life
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."
Wow, is it me or does it feel profoundly counter-intuitive that you'd lose more power over the wire than over radio waves?
You just got troll'd!
...until you consider the security ramifications.
What's the win here? He's capacitively coupling the transmitter to its antenna, or what?
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
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.
Last line of the pdf:
The conventional LTCC package provides 3 times more range than the proposed design but consumes 12 times more power.
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. 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-field transmission to the antenna directly from the amplifier output, without all that intervening cable and PCB trace and such. Near-field antennas can be efficient at *much* smaller sizes, so you can put one on the chip. It's counterintuitive to me that you could get lower losses that way, but that's what he's claiming. Multi-GHz radio waves (microwaves) behave in weird ways, and I'm not an RF engineer...
"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 to the antenna (where the antenna acts like part of the winding) isn't something new. If anything its something very old.
From the research paper:
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.
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...
Why, yes, I AM a Pagan Libertarian.
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.
---- I'll take you in a Hunt deathmatch any day.
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.
Same way you tune a fish.
Check out my sci-fi/humor trilogy at PatriotsBooks.
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.
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.
The article is crap. The paper, however, makes sense. Read it.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
start eating the pringles out of it, that reduces interference with the other components inside. That is a good start IMO
Ph.d candidate... is factual and much less sensationalized.
Oh please, another software engineer? Amplifiers are by their very nature non linear devices as a whole (they just happen to have a linear region which we can make use of). The amplifiers in question are operated within their linear region as much as possible where possible, but certain requirements like efficiency force the designers to drive the transistor partly into its non-linear region (closer to P1dB). Some non-linearity is tolerated and is dictated by the FCC, ETSI or CRTC in the form of emissions masks or by the wireless standard in the form of modulation quality. The only way to ensure the amplifier is always inside the linear region under all conditions would be to back off from P1dB by so much that your efficiency tanks. But that is entirely not feasible for cellular design...consumers like long battery life and carriers like low operating costs.
Now, getting back to your comments. "As long as the mismatch is within spec, the only problem will be reduced efficiency". Amplifiers (or to be more specific, the transistors used in amplifiers) do not have real imput and output impedances. The real (resistive) component will generally not have the desired characteristic impedance (usually 50 ohms) and can be quite small (sometimes a few ohms or even tenths of an ohm). The imaginary (reactive) component will also be non-zero (which is undesirable, but a fact of life) which will tell whether the output (or input) is capacitive or inductive (depending on the sign of the reactive element). Real "high power" amplifiers (I say "high power" to describe the condition where the amplifier is operated towards the upper bounds of the linear region) are not simply matched for maximum power transfer and your done (the input is often matched this way since you would like to ensure any power available to the transistor will actually be taken into the device to be amplified...this is different for low noise amplifiers). This is called conjugate matching (where you set the real parts equal, and negate the reactive part).
On the output a different set of techniques is used. Loadpull is one technique which allows you to design your output matching network not only for linearity, but also efficiency or any other characteristic you can measure. The output matching network that produces the best efficiency (which is what we are talking about here) is most likely not the same as the one that produces the best P1dB or linearity. Also note that conjugate matching or other types of matching do not mean zero reflection (or VSWR=1). By the nature of the networks, the resulting VSWR (albeit low VSWR) is actually part of the desired characteristics of certain matching networks. Put another way, having the best VSWR response (i.e. zero reflection) will not get you the best efficiency (this is the aspect of your post that I take issue with). Reactive components do not dissipate energy (well, if you cosider the small resistive component they do, but this is orders of magnitude smaller than the other resistive components).
All this being said, another way to look at it is that if the reflections occur as part of the matching network, these can be tolerated since they are an inherent part of the design. Reflections after you have reached 50 ohms (i.e. between the matching network and the antenna) can be devastating to an amplifier. This is why they place a circulator or isolator directly after the matching network in most cases...this allows the output of the matching network to see a 20 dB match at least (depending on the circulator) regardless of what happens after (the antenna breaks, cable breaks, etc.). This prevents potentially devastating power from returning to the amplifier.
OMG and you put a 200 lb 10,000 W speaker in my telephone so I can make anyone temporarily deaf in a radius of 30 feet when I receive a text message!! Thank you Xzibit!!!
You just got troll'd!