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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.
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.
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-( )
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
"The on-chip antenna feeds the LTCC patch antenna through aperture coupling, thus negating the need for RF buffer amplifiers, matching elements, baluns, bond wires and package transmission lines."
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.
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.
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.
Less is more.
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.
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!
Ph.d candidate... is factual and much less sensationalized.