Using the Terahertz Spectrum for Wireless Communication

holy_calamity writes "A first step to allowing wireless data transfer over a currently unused part of the electromagnetic spectrum is reported in New Scientist. Terahertz radiation exists between radio and infrared. A new filter created at the University of Utah can filter out particular frequencies, a prerequisite for using it for data. The abstract of the paper in the journal Nature is freely available."

Comments

ridiculously expensive

[evwah]

I regularly work with equipment that produces signals up to 50 GHz and let me tell you... components get much higher in cost the higher in frequency they go. a 3 foot 40GHz cable can cost hundreds of dollars and a 100GHz connector can cost a thousand dollars or more on its own. I imagine that producing and transmitting signals in the terahertz range is not economically viable for most companies.

Re:ridiculously expensive

[markov_chain]

Pshaw, that's nothing. I work with high end audio equipment, and let me tell you, a Hi-Fi 3 foot cable can easily cost several thousand dollars. The 40GHz cable would never be enough, as some people can still hear frequencies in that range.

Re:ridiculously expensive

[sr180]

I see that his joke was above your head by 39.975 MHz or so.

Re:ridiculously expensive

[Profane MuthaFucka]

Are you talking about compact discs? because you can hear vinyl way higher than that.

Re:ridiculously expensive

[Erandir]

I dunno, apparently many companies are already broadcasting in the 450-750 terahertz range, using something called a "light bulb"...

Re:It might just take a while

[Anonymous Coward]

...so communication would have to be rather short-haul as in LAN.

Perhaps TFA should have mentioned that.
 
Wait...

Re:Geek into English.

[rhythmx]

Basically it says that putting the holes in a fractal pattern give much better results than holes in more 'normal' pattern. The rest is Calculus explaining how they can generate patterns that are really good at transmitting a certain frequency.

Sounds really interesting. I wonder if any of this applies to antenna design at average RF.

Re:Hmm,

[NixieBunny]

The microwave spectrum really ends at about 30 GHz, with the frequencies from 30G-300GHz called millimeter wave, and those from 300 GHz up called submillimeter. Terahertz technology is quite in its infancy. There was a terahertz conference last week, so the office I work in was pretty well cleared out. (I work on spectrometers that use what we consider low frequencies, The other thing about terahertz waves is that they behave quasi-optically, being focused by teflon lenses and blocked by cardboard. So it's not a radio band that one would use for cellphones.

Re:It might just take a while

[evilviper]

There is also the slight problem of water absorption of the signal [...] so communication would have to be rather short-haul as in LAN.

Which is EXACTLY what TFA said...

But hey, what do I know, your post is a +5, so it must be somehow insightful, not 100% redundant.

Re:It might just take a while

[NixieBunny]

Are you kidding? you can't do first post if you RTFA!

Not strictly true

[femto]

... a prerequisite for using it for data

It's not strictly true that you need to have bandpass filters to transmit information. There are other ways to select individual users without frequency division multiplexing. For example:

• Do it in the time domain (ultra wideband) using narrow pulses. Each user transmits at a different time.
• Use a spreading sequence to spread the signal so it takes up the entire band, with no need for a narrow filter (CDMA). Each user has a different sequence.
• Use multiple antennas to do space encoding. Users are separated in space, not frequency.

The gotcha is that you need some way of sampling the band. One way is to to use a bandpass filter, mixer and slow sampler. Another is to directly sample (using RTDs???) or in the case of UWB just detect pulses. Bandpass filters are the conventional way of doing it, but not the only way.

Re:Hmm,

[Pink Tinkletini]

...)

Ahhh, much better.

Re:It might just take a while

[psaunders]

Sounds like NRAO-ALMA.

*sigh* It irks me whenever someone posts an obscure acronym without expanding it. Seriously, it's just rude.

For the uninitiated, that is Nothing Really Amazing in Outerspace - Alien Life My Ass.

Re:Hmm,

[Kenshin]

The other thing about terahertz waves is that they behave quasi-optically, being focused by teflon lenses and blocked by cardboard.

So we can finally ditch the tin-foil hats for cardboard hats? About time!

Re:It might just take a while

[DarkAxi0m]

or... it could be for Atacama Large Millimeter/submillimeter Array - National Radio Astronomy Observatory :P

http://www.alma.nrao.edu/

Google can be your friend too.. .

Re:Hmm,

[cyphercell]

Actually, screw names, I'm going to the patent office!

Patents!!!

P.S. - Mod me insightful.

Re:It might just take a while

[Exocrist]

All the better if he's dead on, that just saves the rest of us from having to RTFA!

Re:It might just take a while

[FuzzyDaddy]

http://www.gigabeam.com/technology.cfm has a nice plot of atmospheric absorption versus wavelength. For reference, 100 dB/Km = 3 dB/30 meters - or 50% signal strength loss per 30 meters, not counting the 1/r^2 factor.

Also, generating and modulating signals, with current technology, is done by firing very expensive lasers at very customized pieces of semiconductor materials. As for receivers, NixieBunny would know better then me what the current technology cost and noise figures would be.

All of which to say, this is an interesting article, but it's about 1% of the way towards communications in this band.

Don't get me wrong - this is a cool paper, looks like good work, and this might have some very interesting technological applications. But the perpetual question of "what is it good for?" that every reporter asks (it's got to be a law or something) about every scientific advance misses the point. We don't know what it's good for, but it expands our knowledge of the world, and that can only help us.

Using it for something is the job of the next genius. These guys did enough by getting it to work. Someone else will have to figure out what it's good for.