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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."
I'm not an antenna designer, but by the looks looks of it, the design is basically a miniature on-chip waveguide, efficiently channeling the RF energy toward the external antenna, minimizing wasted radiation.
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.
-=- I tried going insane, and it was fun for a while, but I got bored and decided to go sane. -=-
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
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.
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!