[PLUG-TALK] Spiraling radio waves

[Keith Lofstrom]

On Tue, Mar 06, 2012 at 12:31:03AM -0800, John Jason Jordan wrote:
> Has anyone heard about this?
> 
> http://phandroid.com/2012/03/06/infinite-bandwidth-is-now-a-reality-using-spiraling-radio-waves/

Yes, this is called circular polarization.

http://en.wikipedia.org/wiki/Circular_polarization

You can think of it as a vertical wave followed a quarter wave
later by a horizontal wave. Up, left, down, right, up, left,

Infinite bandwidth is nonsense.  In fact, with line-of-sight
microwave links, you can use the horizontal wave for one signal
and the vertical wave for another, and get twice the bandwidth
of just one polarization.  Not quite, because the two waves
tend to bounce off diagonal stuff and mix together, but close.

Circular polarization can be clockwise and counterclockwise,
and you can do almost the same thing, but unscrewing the two
different rotations can be a bit harder.

Perhaps what the researchers are referring to is that a high
gain antenna (such as a long helix) can give you more
directionality.  Which means you can get more bandwidth through
a given airspace and spectrum.  But so can a planar phased
array, and so can a Yagi (a TV antenna is a Yagi).

And the problem with high gain antennas is that even a tiny
bit of pointing error or vibration or distortion and the gain
plummets, so they are harder to use.  And high gain antennas
are larger than a single 1/4 wave antenna. And you can't do
ultrawideband with a single high gain antenna, they tend to
be tuned to a narrow frequency range.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs