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Magnets To Replace Bluetooth?
aceat64 writes "News.com is carrying a story that suggests magnets could eventually replace Bluetooth as a cheaper and more energy effiect wireless solution. The concept of magnetic induction isn't new, but Aura has managed to shrink the technology onto a single chip. The first device to be made using the technology is a wireless headset that will cost between $60 and $80."
The magnetic approach also consumes very little power when compared with notorious battery-draining RF techniques like Bluetooth. According to a description on the Aura Web site, Fonegear's headset can keep going for up to three months on a single AA battery, as opposed to only a number of hours for equipment outfitted with Bluetooth.
Developed in the late 1950s, magnetic induction never really caught on
Gee, silly me, and I always thought Faraday developed "magnetic induction" and that it was in wide use. But, hey, it has turned out that, contrary to my own silly ideas, Gates actually invented the Internet and that BT invented the hyperlink, so I must be wrong on Faraday as well.
Correct me if i'm wrong but dont most Radio transmission technologies use some form of magnetic induction in order to achieve their goal.
The point is using magnetic fields and mutual inductance rather than electromagnetic radiation to transfer information wirelessly.
Last i heard passing electricity through a coil produces a magnetic field.
More precisely, passing an alternating current through any conductor will produce a magnetic field. This magnetic field in turn will create a current in another conductor some distance away (the article sites four feet as the maximum distance) which can be used to observer the original signal.
It's an old concept, but since magnetic fields created by normal AC powers are pretty weak it's not really that useful. Apparently they've managed a very-high frequency (the effect is proportional to the change in current) alternating current in a chip small enough to make this possible.
I assumed that they would just be modulating the magnetic field with the signal rather than modulating a carrier signal with a high frequency.
The description above is nothing like I heard in physics at school but it may be that lower frequency signals have a shorter range.
A broadcast antenna is a magnet, an electromagnet, one that changes polarity many times per second, and that varying electromagnetic field is what induces a response in the receiving antenna. This is called radio transmission (see Marconi, or better yet look up Heinrich Hertz or James Clerk Maxwell.) If this so-called technology is claiming to transmit information using a static magnetic field they are full of little red ants. Phooey.
The higher the technology, the sharper that two-edged sword.
Like many here, I was very skeptical when I read this article -- the reporter is clearly a total sci/tech ignoramus (you gotta love the totally redundant "cordless cell phone").
So I went to Aura's website for more info. Here's their blurb:
While the concepts behind magnetic induction communication have been around for decades, Aura's engineers are the first to develop and implement practical solutions capturing the benefits of this technology.
Conventional radio frequency (RF) wireless communication systems are optimal for sending large amounts of information and communicating over long distances. However, this consumes power, creates information security issues, and results in interference and "crowding" among devices. A good example is in the 2.4 GHz band where simultaneous operation of a cordless phone, WiFi network and Bluetooth headset is frequently not possible without severe degradation of Quality of Service. In sharp contrast, LibertyLink's magnetic communication operates in a "bubble" that envelops the personal space of each user and is - by the laws of physics - inherently private and secure. The result is an easier to use, lower-cost system that makes far more efficient use of power and bandwidth than conventional RF solutions. By selecting a technology that limits the range and bandwidth to only what the application requires, Aura achieves a very substantial savings in power with all of the simplicity advantages of LibertyLink: dedicated communication channels, no bandwidth sharing, complete frequency re-use between bubbles, worldwide regulatory flexibility, and reliable coexistence with WiFi, CDMA, TDMA. and GSM transmissions.
Still pretty vague -- how the hell do they handle interference issues in this "magnetic bubble"? Do they supply Faraday cages for your PC/monitor?
1 - They complement each other, yes, and they are intimately interrelated.. but they are not the same thing (for practical purposes). If you have a bar magnet in front of you, is their an electric field around it? no, there isn't.
2 - A cruise of the whitepapers indicates that the magnetic field strength is related to distance via 1/d^6, as opposed to radiated power, where it's relatd to 1/d^2. This means a much sharper dropoff in power... meaning the point beyond which there is a negligible power level is much sharper.
3 - A magnetic field and RF radiation are not the same thing.. one transmits energy over distance (RF).. the other puts that energy into sustaining a field (Magnetic)
4 - What you are saying about frequencies applies to RF. This is not about RF. The mention of a high frequency, relatively unused ISM band probably refers to the EM side effects of the devices. (a 10Ghz oscillator, even if it's used via induction, sitll creates a 10Ghz EM signal)
5 - "Used by Industrial, Scientific, and Medical" as they said in the article, is most likely just the reporter trying to sound smart.. but that's usually abbreviated as "ISM", and covers the fun 900Mhz and 2.4Ghz bands we already love and know, as well as others....
6 - interference is not an issue for practical purposes because this thing has a high field strength within the bubble, and virtually none outside. Any inteferer would have to be really strong, or really close.
did you RTFA?
CNet claims "Magnetic induction differs from Bluetooth and just about every other wireless technique now available, most of which use what's known as radio frequency, or RF, signals--bursts of electrical energy that waft out like ripples in a pond until they reach an antenna.
Magnetic fields also create waves, but the waves form a kind of bubble, which stops growing after four feet, making them more secure than waves wafting endlessly in every direction, Cui said."
I think the author of the article was shooting for 5-funny.
It's vague, but I think this means it it using the "near field" instead of the propagating field. A transmitting antenna emits two fields: a propagating electromagnetic wave (i.e. light) whose intensity drops off like 1/r^2, and a nonpropagating electromagnetic field that drops off like 1/r^4 (which is why it's called the near field). It can carry a lot of power, but since it doesn't go anywhere it is usually ignored.
If we were ants living on a Rubik's cube, differential geometry would be a little more confusing.
I really hope you're just trying to be funny and doing a poor job of it, but in case you're serious...
I keep waiting for a gas pump that "recognizes" my gasoline credit card device and waits for me to "fill it up."
Uh, hate to break it to you, but those have been around since the mid to late 90's, when Mobil introduced the SpeedPass. I've had one since long before I ever heard of Bluetooth. Now they are used at Exxon and Mobil stations all over the place. I think McDonald's even did testing a while back in California, IIRC, where people could pay for their drive-thru purchases via SpeedPass-- dunno if that's going to go national. When they launched it, it came in two varieties-- a small cylinder for your keyring that must be waved in front of a spot on the pump, and a transponder meant to be stuck inside your car's window that is "read" by an overhanging antenna when the car first pulls up to the pump (sort of like the E-Z Pass system some states have for toll roads). I think the stick-on transponder SpeedPass has been phased out, because I see no reference to it on the website.
Have a hard time getting a paper receipt, though. Keep getting a message saying "Your receipt is inside."
Where I live, gas pumps have been accepting credit cards right at the pump for at least 10 years, and have been printing their own receipts right at the pump as well. My SpeedPass account is even configured to assume I want a receipt when I gas up, so the pump just spits one out without asking when I'm done filling my tank.
I won't even tell you what I can do with my Macs running OS X and my Bluetooth phone, it may make your head explode. No flying cars yet, though.
I suggest you move to a state where people aren't too busy dating their relatives to embrace technological advances. By the way, the North won.
Correct me if i'm wrong but dont most Radio transmission technologies use some form of magnetic induction in order to achieve their goal. Last i heard passing electricity through a coil produces a magnetic field. Whats new here?
What's new is that they've goofed.
At any given frequency you can launch an electromagnetic wave by using:
- And electric dipole. (Essentially impossible at anything above DC due to the current from the moving charges.)
- A permanent magnet or a current loop (producing a virtual magnetic dipole).
- A combination of the two, to produce the electric and magnetic fields simultaneously.
With a current loop the field very near the loop is essentially pure magnetic and falls off as the first power of distance (as more of the wire's length becomes signficant to the observer).
Moving out a bit more, in the first two the field moderately NEAR the antenna is essentially pure electric or magnetic (respectively) and falls off as a dipole field - with the cube of the distance. (Inverse square for each "pole" of the dipole, times inverse first-power for the smaller angular separation of the poles as viewed by the distant observer.) In the third you get the same effect with both the electric and magnetic field, typical of ordinary antennas.
But the changes to the electric field produce a magnetic field, and vice-versa. By the time you're a wavelength or so away from a simple driven element an electromagnetic field - a "radio wave" - has peeled off. This weakens at inverse-square rate (once you're far enough from the emitter that local additions and cancelations from different parts of it don't confound the issue.)
For signals in the tens of kilohertz and less (audio, for instance), a wavelength is very long. So a coil acts like more like a dipole than an antenna for a long way. Inverse-cube attenuates the signal rapidly with distance (though a strong amplifier can pull it back up - along with any competing noise).
But for computers you'll probably want this to operate at high speed - for images, disk access, etc. Now you're talking megahertz - with coding schemes that end up putting essentially all the informaiton at high frequencies. So the radio-wave effect takes over quickly, and the signal propagates without serious attenuation, regardless of whether the emitter is a magnetic loop (B-field) or electric dipole (E-field) emitter.
The guys operating the TEMPEST equipment will LOVE this system, thanks to the unjustified feeling of security it will give the user.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
N&V covered this in the June 2003 issue along with RFID and UWB. Page 22 for those who can get access to a backissue (say at the library or somewhere like that)
One problem (that's easily fixed) with the magnetic system is that both transmitting and receiving coils have to be parallel. If they're at 90 degrees little or no signal gets through. The fix for it happens to be using 3 coils, each one 90 degrees from each other on the receiver. The transmitter only needs one, but no matter how that one is oriented one of the 3 coils in the receiver can pick it up. I haven't heard of any other chips, but the LibertyLink chip from Aura Communications can automatically select the coils on it's own.
Very short range, but it works for something like a wireless headset where range doesn't matter anyways.
By contrast, magnetic fields have a very measurable effect on the body. Your blood is composed of about 7-28 umol/L, or if I did the math right, about 1 mg/L. Take a magnet and rub it near a vein sometime. If the field is strong enough, you get reorientation of the red blood cells, and eventually clumping of those cells. In sufficiently concentrated doses, the health effects could be significant.
That's false. Red blood cells do not clump in the presense of magnetic fields.
There have been studies on the phosphene effect, where strong magnetic pulses cause subjects to percieve brief visual images.
Lawrence Livermore National Labs has a page on the harmful effects of very strong magnetic fields, upwards of 40,000 Gauss -- but such fields are rarely encountered. Typical MRI magnetic fields, by comparison, are typically between 5,000 and 20,000 guass. But even in very high static magnetic fields, the effects are temporary.
The big danger is for people with implanted metal, like pace makers or surgical clips.
Now, I did find a study on red blood cells in very strong magnetic fields that does suggest that they reorient, even in fields as low as 10,000 Gauss. No mention of clumping.
Your typical hand-held magnet, even a strong one, produces a field on the order of 4,000 Gauss. Not harmful.
The fields produced by any kind of transmitters mentioned in the article would be tens or hundreds of Gauss -- too weak to move a paperclip.
(The earth's magnetic field is about 0.5 Gauss, for comparison)
On the other hand, the LLNL page mentions that magnetic fields equal to the strength of the Earth's can disrupt circadian rhythm! And it has been proven that birds are sensitive to the Earth's field... so even small magnetic fields can have a measurable biological effect.
But FEAR FEAR FEAR is not warranted.
- Peter
INsigNIFICANT
The data rate is 204.8 kilobits/sec - I can't tell if that's bidirectional or shared unidirectional like Ethernet? However, you're wrong about your use of Nyquist's formula - that tells you that your pulse sampling rate has to be twice the frequency of a continuous wavelength you're trying to send (so your data rate needs to be N*2 samples/sec for a N Hz audio signal). This is the other side - Shannon's formula is that if you want to carry a given bit rate using an analog signal, the bit rate you can get is (IIRC)
Bandwidth * log (1+Signal/Noise)
which means that if your signal/noise ratio is arbitrarily good, you can get an arbitrarily high data rate
The place that Nyquist bites them is that with only a 204.8 kbps data rate, it limits their audio capabilities. They're actually using 64kbps CVSD for their audio, which is kind of an odd choice of codecs - maybe they're sampling at a higher rate than telephony, or maybe they're figuring it will do less or different damage to the signal than the GSM or G.723 codecs used by the phone? In either case, CVSD is a simple codec that doesn't need much CPU horsepower, and a little better than ADPCM at that speed.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Perhaps the easiest way to explain this technology is that it's simply a type of transformer.
:-)
One coil creates a varying magnetic flux that induces a current in a matching coil -- and thus an electrical signal is passed through the ether.
Those who claim that it's no different to a radio link are almost right -- the only real difference is that with such a system there's no need to use a carrier wave (RF) -- the information can be dumped (raw) into the transmitting side of the coil and received by the other coil.
There's no rocket science here -- all that's happened is that some crowd has figured out that by using three coils instead of one, they can effectively adjust the direction of the strongest flux lobe to give the maximum transfer of energy.
Of course, the marketing droids would never simplify things by simply telling us it was a "clever transformer" because then they couldn't charge so much for it eh?
... which means you don't have the security. Bluetooth also runs over RF - it's more than protocol on top of an independent bearer. I'm very surprised that you have people using a bad system in Japan when you have the hardware to use a good one.
..
Yes, I work in the telecom industry
it's in my head