On Tue, 7 Oct 2008 11:49:59 -0500, (Richard
Harrison) wrote:

Dr. Nathan Cohen (Chip) is founder of Fractal Antenna Systems, Inc. He
is also a professor of Applied Science and Telecommunications at Boston
University.

I have no idea what "fractal theory" means. It's not a theory. It's
a mathematical alogorithm with divisible self-similar properties that
can be applied to antenna design.

Their web site seems to have been suspended for some reason.
http://www.fractenna.com/
is getting redirected to:
http://ns4.netatlantic.com/suspended.page/

Overview and references:
http://en.wikipedia.org/wiki/Fractal_antenna
Note that the article hints that a fractal antenna are intended to
maximize the element lengths through self-similar repetative patterns.
Whether a fractal (tubulence model) or a random meandering array is
more effective is subject to some debate. Fractals may have a more
efficient packing factor. (note: I don't pretend to know any more
about fractal antennas than I've read).


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Oct 7, 1:19*pm, Jeff Liebermann wrote:
On Tue, 7 Oct 2008 11:49:59 -0500, (Richard

Harrison) wrote:
Dr. Nathan Cohen (Chip) is founder of Fractal Antenna Systems, Inc. He
is also a professor of Applied Science and Telecommunications at Boston
University.

I have no idea what "fractal theory" means. *It's not a theory. *It's
a mathematical alogorithm with divisible self-similar properties that
can be applied to antenna design.

Their web site seems to have been suspended for some reason.
http://www.fractenna.com/
is getting redirected to:
http://ns4.netatlantic.com/suspended.page/

Overview and references:
http://en.wikipedia.org/wiki/Fractal_antenna
Note that the article hints that a fractal antenna are intended to
maximize the element lengths through self-similar repetative patterns.
Whether a fractal (tubulence model) or a random meandering array is
more effective is subject to some debate. *Fractals may have a more
efficient packing factor. *(note: I don't pretend to know any more
about fractal antennas than I've read).

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

That is exactly correct. The fractal antenna is an optimised meander
antenna where
the radiator "packing" per unit space is superior. It is just that a
fractal pattern has a
mathematical background where impedance can be garranteed where-as a
meander line design is subject
to human error. I see no reason why one antenna should be seen as
"better" than the other
if the radiating length and the unit areas are the same. I also see
this as another example where people talk down on this antenna
as a way of resisting change. Obviously industry see it as
particularly usefull especially with encapsulated designs and Chip is
making a lot of money
despite the dirisivenes of the "experts" on the newsgroup..
Art

Roy Lewallen wrote:
Richard Harrison wrote:
Roy Lewallen wrote:
"What`s fractal theory?"

The IEEE lists a paper appearimg in "Antennas and Propagation 2007".
EuCAP 2007.

Claims are size can be shrunk from two to four times without much loss
in performance, and that the antenna is naturally broad in bandwidth.
Two criteria must be met. The antenna must be symmetrical about a point,
and it must be self-similar, having the same appearance at every scale.

Dr. Nathan Cohen (Chip) is founder of Fractal Antenna Systems, Inc. He
is also a professor of Applied Science and Telecommunications at Boston
University.

Best regards, Richard Harrison, KB5WZI


As some of the longer term readers of this group might recall, the same
or superior characteristics can be obtained by shrinking antennas by
having their perimeters follow a random, rather than fractal, path. A
random meander pattern submitted by Dr. Steve Best, who also wrote
several IEEE papers on the subject, was shown to be superior to a
fractal design in the quality factor criteria put forth by Chip in a
"challenge" the latter publicized here some years ago (2000). Anyone
interested is encouraged to go to http://eznec.com/misc/MI2/, read the
0Notes.txt file, and download and look at the various competing designs.
The designs are in the form of EZNEC files, which can be viewed with any
EZNEC program type including the demo.

But this doesn't explain what "fractal theory" is, unless it means the
creation of antennas whose perimeters follow a fractal curve. In that
case, "fractal theory" hasn't been shown to be superior to "random
theory", and in some ways really no better than "square theory" or
"round theory". Sounds a lot better when trying to talk potential
investors into reaching for their wallets, though.

Before we get too far off base here, Fractal theory does not refer to
fractal antennas. It is an entire field that might be characterized as
the science of self similarity.


Somehow I see Richard C. making a comparison any moment here in his
latest skirmish with a couple other posters...... ;^)

- 73 de Mike N3LI -

On Tue, 7 Oct 2008 11:37:54 -0700 (PDT), Art Unwin
wrote:

That is exactly correct.

Thanks. However, having you endorse my pontifications makes me worry
that I may have said something wrong, or made a mistake. I'll double
check.

The fractal antenna is an optimised meander
antenna where
the radiator "packing" per unit space is superior. It is just that a
fractal pattern has a
mathematical background where impedance can be garranteed where-as a
meander line design is subject
to human error.

There are various tests for randomness.
http://www.ciphersbyritter.com/RES/RANDTEST.HTM
Random number generators are well developed.
http://www.random.org
I see no reason for "human error" unless you use a coin toss or dice
throw to design your antennas, which would be quite tedious.

I see no reason why one antenna should be seen as
"better" than the other
if the radiating length and the unit areas are the same.

I do. Trying to shoe horn efficient radiators inside a small package,
such as a cell phone is not a trivial exercise. There are lots of
compromises that can be made if the design is constrained in size,
such as tolerating a high VSWR, strange pattern, and bandwidth
limitations. Incidentally, the primary limiting factor is size,
followed by SAR (specific absorption rate). Gain and pattern are
lesser priorities. VSWR is somewhere near the bottom.

I also see
this as another example where people talk down on this antenna
as a way of resisting change.

Resisting is a complex problem, that includes imaginary parts. Any
reactance introduced into your change will convert your resistance
into an impedance. Think of it as people impeding change, not
resisting change.

Obviously industry see it as
particularly usefull especially with encapsulated designs and Chip is
making a lot of money
despite the dirisivenes of the "experts" on the newsgroup..

Ummm.... where do I collect this money? I could tell a few stories
about chip antenna companies, but I'm sworn to simulated ignorance.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 07 Oct 2008 12:22:00 -0700, Jeff Liebermann
wrote:

I also see
this as another example where people talk down on this antenna
as a way of resisting change.

Resisting is a complex problem, that includes imaginary parts. Any
reactance introduced into your change will convert your resistance
into an impedance. Think of it as people impeding change, not
resisting change.

Hi Jeff,

You have quoted one of Art's more cryptic statements, especially when
he hasn't the vaguest notion of what a fractal antenna is and has
talked it down on many occasions when I suggested he visit a site with
more 300 pages of modeling and measured results:
http://www.qsl.net/kb7qhc/antenna/fractal/index.htm

This stuff is over a decade to 15 years old, and possibly contains
(long) prior Art now found in (new) patents claiming to be original
work. ;-)

I worked out a general rule for fractal design, but it is of academic
interest only, and is distinguished in that role by its lack of
discussion here. ;-)

In fact, I can well imagine Art, in high dudgeon, would furiously
refuse to go there. I mention this only because that vaudevillian act
is so outré as to be camp Art.

The test for this distinguished role follows from it being discussed
hereafter, or the language of this posting. :-0
(I vote for Artré.)

73's
Richard Clark, KB7QHC

Please folks, put "fractal" in the Subject: header for this BS
so that my filters (and many others, I'll bet) can 'process' it.

Richard Clark wrote:

I worked out a general rule for fractal design, but it is of academic
interest only, and is distinguished in that role by its lack of
discussion here. ;-)

And it can be distinguished from works of academic interest by its lack
of discussion everywhere else. :-)

ac6xg

Jim Kelley wrote:

...
And it can be distinguished from works of academic interest by its lack
of discussion everywhere else. :-)

ac6xg

Other than biological sciences, studies in probability and statistics
and those exploring chaos (well, perhaps the art world--no pun intended
grin ) ... it seems you are quite correct.

Regards,
JS

On Wed, 08 Oct 2008 11:23:09 -0700, Jim Kelley
wrote:

Richard Clark wrote:

I worked out a general rule for fractal design, but it is of academic
interest only, and is distinguished in that role by its lack of
discussion here. ;-)

And it can be distinguished from works of academic interest by its lack
of discussion everywhere else. :-)

Can't argue with that.

These fractal threads usually start with trolls (the original poster
was certainly so qualified), and fill up with more soon after.

73's
Richard Clark, KB7QHC