"Engineered metamaterials enable remarkably small antennas"

Check this out. Although the experiments were, um, conducted at UHF, I
wonder if this development will have any implications for future HF
antennas, especially for those who have to live with CC&R's!

http://www.physorg.com/news183753164.html

The text is provided below.

Howard N7SO

NIST engineers are working with scientists from the University of Arizona
(Tucson) and Boeing Research & Technology (Seattle, Wash.) to design
antennas incorporating metamaterials—materials engineered with novel, often
microscopic, structures to produce unusual properties. The new antennas
radiate as much as 95 percent of an input radio signal and yet defy normal
design parameters. Standard antennas need to be at least half the size of
the signal wavelength to operate efficiently; at 300 MHz, for instance, an
antenna would need to be half a meter long. The experimental antennas are as
small as one-fiftieth of a wavelength and could shrink further.

In their latest prototype device, the research team used a metal wire
antenna printed on a small square of copper measuring less than 65
millimeters on a side. The antenna is wired to a signal source. Mounted on
the back of the square is a "Z element" that acts as a metamaterial—a
Z-shaped strip of copper with an inductor (a device that stores energy
magnetically) in the center (see photo).

"The purpose of an antenna is to launch energy into free space," explains
NIST engineer Christopher Holloway, "But the problem with antennas that are
very small compared to the wavelength is that most of the signal just gets
reflected back to the source. The metamaterial makes the antenna behave as
if it were much larger than it really is, because the antenna structure
stores energy and re-radiates it." Conventional antenna designs, Holloway
says, achieve a similar effect by adding bulky "matching network" components
to boost efficiency, but the metamaterial system can be made much smaller.
Even more intriguing, Holloway says, "these metamaterials are much more
'frequency agile.' It's possible we could tune them to work at any frequency
we want, on the fly," to a degree not possible with conventional designs.

The Z antennas were designed at the University of Arizona and fabricated and
partially measured at Boeing Research & Technology. The power efficiency
measurements were carried out at NIST laboratories in Boulder, Colo. The
ongoing research is sponsored by the Defense Advanced Research Projects
Agency.


More information: R.W. Ziolkowski, P. Jin, J.A. Nielsen, M.H. Tanielian and
C.L. Holloway. Design and experimental verification of Z antennas at UHF
frequencies. IEEE Antennas Wireless Propag. Lett., 2009 vol. 8, pp.
1329-1332


Provided by National Institute of Standards and Technology (NIST)

On Mar 3, 8:45 am, "Howard Lester" wrote:
"Engineered metamaterials enable remarkably small antennas"

In their latest prototype device, the research team used a metal wire
antenna printed on a small square of copper measuring less than 65
millimeters on a side. The antenna is wired to a signal source. Mounted o
n
the back of the square is a "Z element" that acts as a metamaterial a
Z-shaped strip of copper with an inductor (a device that stores energy
magnetically) in the center (see photo).


Well, the old saying "you cannot change physics" will still apply.
Getting something to launch energy into space is not that hard, even
dummy loads do that. Making it an efficient process is a bit more
difficult. The ISOTRON antennas do "work" (I own three of them) but
they are really poor devices for launching energy into space (unless
you count heating the attic). They work better than my dummy load,
but not by that much considering what they cost.

Don't we already have 1/4 wavelength verticals that are pretty good at
launching energy into free space? The article says they can cut that
down to 1/5 wavelength. That takes a 10 Meter antenna and makes it
into an 8 meter antenna, what’s the big deal with that?

Does somebody know the maximum efficiency of a 1/4 wave vertical and
how does that compare to 95%? (Even with almost perfect ground
resistance?)

I'm thinking they may have succeeded in making a low resistance
material that cuts down on IR losses, but I got a feeling the advanced
materials will be way to expensive to use for your average HF rig
running 100 W given the efficiency and cost of what we already have.

-= bob =-

On Mar 3, 2:28 pm, KC4UAI wrote:

Does somebody know the maximum efficiency of a 1/4 wave vertical and
how does that compare to 95%? (Even with almost perfect ground
resistance?)

It's right up around there.

Anyhow, if they have managed to make this antenna extremely efficient,
what they must have done is make the RF resistance not become much
lower as the physical size goes down. Some other possibilities are
that they somehow managed to make the Velocity factor really low,
maybe 25 percent.

Seems like once a year or so, some outfit makes some claims like this.
A couple years ago it was a University on the east coast announcing a
antenna that was so efficient that the original one burned up when
they sent a hundred watts through it. I personally think that is
speaking to inefficiency, but I'll note that statement was removed
from the press release.

I'll believe it when I see it.

- 73 de Mike N3LI -

Michael J. Coslo wrote:
On Mar 3, 2:28 pm, KC4UAI wrote:

Does somebody know the maximum efficiency of a 1/4 wave vertical and
how does that compare to 95%? (Even with almost perfect ground
resistance?)

It's right up around there.

Anyhow, if they have managed to make this antenna extremely efficient,
what they must have done is make the RF resistance not become much
lower as the physical size goes down. Some other possibilities are
that they somehow managed to make the Velocity factor really low,
maybe 25 percent.

That's exactly what is being experimented with; materials that make the
velocity factor low.

Now how you do this without getting big losses in that material, I haven't
a clue, but evidently some people think they can do it.


--
Jim Pennino

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