Wireless breakthrough: one frequency, multiple signals

Okay people, if you have a circular mirror shaped like the dish in the picture, and you shine a light against it, does the light SPIN off of it? NO it does not. RF acts the same way. It doesn't spin, either.

Given the distance between the split surfaces of the dish, taking into account the speed of light at which RF travels, I highly doubt that these guys would get two discrete signals over any line of sight distance on the planet.

I am highly skeptical of this.

Originally posted by -PLB-
It looks interesting, but from what I understand of it, it only works in a fixed direction. So the antennas requires to be pointed exactly towards each others. Practical applications may be satellites and other long distance connections, but I don't see how it would work for any mobile device, as the direction the antennas are pointing to is constantly changing. I may be wrong though.

Yes, the setup as originally described does use specific spatial orientations in transmitter & receiver.

Calling it 'orbital' vs 'spin' angular momentum (referring to polarization) is a bit of a fluff.

At the frequencies and intensities involved, this is all 100% classical physics from Maxwell's equations. If you impart twist at space scales near or smaller than a wavelength they'd call it "spin" angular momentum vs "orbital" angular momentum. But it all relies on the fact that E&M has 3 propagating vector field (though no longitudinal component), and you can modify it spatially as well (which is what this group is doing). I think this is a continuous-space version of "MIMO", multiple-input-multiple-output transmitter/receiver which is already a developed technology.

In a practical sense the big problem is scrambling of all the spatial information after reflection & refraction. If you take a modulated FM signal, for instance, even though you have all sorts of spatial interference/reflection etc, you can still pick it up well. Why? Because interaction with the ground or trees or buildings won't change the carrier frequency or, especially, the modulations of that frequency. (You would need active transmitters to do that, known as electronic counter measures). That's why FM was the first high-quality radio system---you can both transmit the signal well and after inventing superheterodyne it's practical to demodulate with a few analog components.

The natural environment, on the other hand, will naturally scramble nearby spatial patterns.

I'll play product manager for free....so here goes...:

Market: The best application for this will be large-bandwidth satellites, where you have line-of-sight connectivity at high frequencies. The NSA & NRO contractors will be all over it---you might be able to get the benefits of MIMO in a large antenna just by clever physical design, without requiring the typical engineer's brute-force approach, a huge number of active components in an array all sucking down valuable and limited electrical power. You would need as many individual transmitters as signals [can't get around that], but use passive physics instead of active array modulation to apply the spatial modulation.

Technological future: The current system applied two different spatial patterns with a classical symmetry. That might not be the ultimate---you could imagine multiple transmitters/recievers on some kind of 'fractal' or otherwise spatially complex antenna, and then a a very smart reciever (which is is possible now) which untangles the N independent spatial patterns that it detects with a complex geometry receiver. Advances in machine learning & signal processing in the last 15 years or so have greatly improved the capability of blind-source separation, something like ICA (independent component analysis) could possibly even be implemented in hardware at GHz speeds, with some major effort. One advantage of using adaptive learning methods is that you may be able to ameliorate the spatial scrambling effect from scattering. Scattering might change the geometrical relationships, but as long as there are N distinctly separable spatial patterns (as natural objects will not have the specific spatial complexity of the transmitter), you could likely recover them.

I'll coin this as "spatial-code-division-multiple-access" (S-CDMA) --- applying encoding/decoding analogous to the time-series codes, but in x,y,z instead of in t.

Originally posted by davespanners
Did these guys come up with this "idea" after reading this wiki page about circular polarization? Or is this something different?

Sure looks the same from the illustrations

It's very similar, but using the idea that you can have signals that are different in a certain way when you move the spatial location of the center-line, and this modulation was applied by the physical design of the transmitter. Notice that the size of the dish is bigger than the wavelength---this is important to make it work.

At high frequencies, like say light, that's what's happening on the screen that you're looking at right now.

I don't think it's BS, the theory was published in Physical Review Letters---might be wrong, but not in an obviously stupid way.

Thank you again all for contributing, in particular mbkennel! I've read your post a couple of times, trying my best to understanding precisely what your saying, but I'm struggling a bit But from the jist of what you say, I'm not going to get better HD am I????

reply to post by Submarines


Here is a link to a wika article about circular polarization.

Circular Polarization Here

One of my fav professors, Dr Cloud taught the antennas class at LTU where I went to school for engineering. He said some antennas are so complicated, so strange that they can not be simulated. Some of them, no one really understands why they work. Someone just decided to try an odd shape and it worked...

Antennas are one of my favorite subjects. I think the Italians may be pulling our leg on this one.

I was on Dixon 1987 to Apr 1990. Worked in the cal lab. ET1. I really miss the 80's.

Originally posted by THE_PROFESSIONAL
reply to post by definity

 

TDM = multiple signals spread across time (different times)
FDM = multiple signals spread across spectrum (different frequencies)
Polarization
Wavelength division (for fiber optics)
OFDM = a bit more advanced.

The communications technologies are a big group of new things to look into.
If I was starting off in college I would be looking into careers in wireless engineering or something similar.

Yeah i did telecomuinication in college but the idea of a analog type polarity change using digital signals just seams clunky. and yes TDM might be able to fit a diffrent signal in every 0.00000009 seconds but can a dish do a complete revolution in 0.000000009?

P.S dont quote me on how maqny zeros i did!