have been a mathematical curiosity since first being popularized by
Benoit Mandelbrot(who coined the term) in the 1960s. Perhaps, and in retrospect
no coincidence, was the popularity of the cloaking concept featured in the 1960s phenomenon
called Star Trek. I say coincidence
because who would have guessed that some of the leading research in invisibility cloaking
would involve barriers derived from fractal forms? Have aliens been guiding the technology?
If so, maybe they're working at Fractal Antenna Systems, because in mid December the
company issued a press release
detailing work being done on a cloaking system that works in the microwave band
(as opposed to visible light) - chosen for convenience
of size. Results are quite impressive as can be seen in the videos.
I am not totally convinced that fractals are a necessary part of cloaking, but they
do make for interesting publicity photos. After all, if fractals are part of the cloaking
equation, then wouldn't fractal-shapes in nature like coastlines and foliage help make
them invisible to something noticeable - sound, light, and/or water waves? The magic
is probably in the increased projected surface area generated by a fractal's stepped
outline. A multitude of similarly dimensioned curved surfaces might actually be better,
but curves are broken down into polygons for computer modeling, so that still leaves
you analyzing multifaceted flat surfaces.
(Waltham, MA--21 Dec 2010) Can you see it? Researchers at Fractal Antenna Systems
have written a new chapter in the science of making things disappears. Their wideband
microwave invisibility cloak, first revealed in March 2009, now makes its debut for everyone
to see in a new video: http://fractenna.com/whats/whats.html
The video conclusively shows that invisibility science has taken a huge leap with
fractal design. Fractals are geometric patterns that have complex structure built from
scaled repetition of a simple pattern. Fractals make up the cloak and its 'object' layer,
producing a wideband invisibility that slipstreams microwaves around obstacles. The other
side appears with good fidelity, without the detectable presence of the obstacle. Although
a proof-of-concept of an invisibility cloak was shown in 2006 at Duke University, such
non-fractal efforts had limitations. The Duke cloak worked in one narrow band, had many
more cloaking layers, possessed a discernable shadow, and required the obstacle to already
be hiding behind a mirror. All of those obstacles have been solved using fractals, in
grids called fractal metamaterial, as the firm's cloak reveals.
Holy Grail of Cloak Design
Notes the firm's CEO and chief inventor Nathan Cohen: "In 2008, Chinese researchers
said it was impossible to make a wideband invisibility cloak. We not only did it, but
reduced the number of cloak layers, and, most importantly, made a cloak you can see out
of. That means a sensor, for example, can be made to disappear into the background over
a wideband, but still be able to see what's outside. These attributes are really the
'holy grail' of cloak designs, and strongly point towards a bright future for invisibility
The fractal cloak works at microwaves; radio waves used by cell phones and wireless
devices. The technology directly applies to infrared, and with technology advances in
nanotechnology, can be made to make visual light invisibility cloaks, although Cohen
cautions that it will be many years before visual light invisibility cloaks are perfected.
"Other researchers are still hiding objects behind mirrors. What's the point of a cloak
if you are already hiding behind a mirror?" asked Cohen.
The firm's cloak also marks the steady and remarkable process of innovation afforded
by fractals in antennas and electronics. Oddly, many American antenna researchers have
shied away from fractal design, while interest in Asia and Europe bloomed, noted Cohen.
However, as recently shown on PBS's NOVA television program, fractals have a great impact
on antennas and electronics, and researchers from all continents except Antarctica now
boast many dozens of active research programs.
Cohen also believes that success in cloaking science requires a body of diverse knowledge,
which in his case drew upon experience as an astronomer, and curiously, as a radio ham
operator. "I have a Ph.D. in astrophysics and am a retired college professor. But the
experience I gained as a young ham radio operator was invaluable in helping me make knowledge
connections to make the cloak work. That's, in part, why my research group did this first,
and why we continue to lead in innovation in fractal electronics, both in basic research
and application to products."
Fractal Antenna Systems, Inc.
Fractal Antenna Systems, Inc. (http://www.fractenna.com)
supplies products for the world's most demanding wireless, and electromagnetic applications.
Backed by over three dozen U.S., and international patents, plus dozens of patents pending,
Fractal Antenna Systems is the recognized pioneer in fractal technology, with extensive
research and field experience over 15 years in business. The company is a privately held
and headquartered in Waltham, Massachusetts, USA.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas
and reference material while performing my work as an RF system and circuit design engineer.
The Internet was still largely an unknown entity at the time and not much was available
in the form of WYSIWYG
All trademarks, copyrights, patents, and other rights of ownership to images and text
used on the RF Cafe website are hereby acknowledged.