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Are fractal antennas being used in cellphones?
According to the July 1999 issue of Scientific American (available
online at http://www.sciam.com/article.cfm?art...B7809EC588F2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) Just why these fractal antennas work so well was answered in part in the March issue of the journal Fractals. Cohen and his colleague Robert Hohlfeld proved mathematically that for an antenna to work equally well at all frequencies, it must satisfy two criteria. It must be symmetrical about a point. And it must be self-similar, having the same basic appearance at every scale--that is, it has to be fractal." |
this is a very good question
why couldn't we have a big rubbery fractal that folded up so to say. They have them stuck inside the unit and your have is wrapped around the antenna, no such a good idea, why not make it in a rubber matrix and be about 2" * 4" folding up. That would be goog for added sensitivity I would suspect Paul (EE) totojepast wrote: According to the July 1999 issue of Scientific American (available online at http://www.sciam.com/article.cfm?art...B7809EC588F2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) Just why these fractal antennas work so well was answered in part in the March issue of the journal Fractals. Cohen and his colleague Robert Hohlfeld proved mathematically that for an antenna to work equally well at all frequencies, it must satisfy two criteria. It must be symmetrical about a point. And it must be self-similar, having the same basic appearance at every scale--that is, it has to be fractal." |
On Sun, 07 Sep 2003 15:29:55 GMT, Paul Victor Birke
wrote: This is a very good question!! Unfortunately for such a good question, the answer reveals a mediocre reality compared to the glowing claims. Why couldn't we have a big rubbery fractal that folded up so to say. Proximity often leads to increasing loss, and rarely opportunity for boundless gain. They have them stuck inside the unit and you have your hand wrapped around the antenna-not such a good idea since you are conducting, at least partially, and therefore shielding the inside antenna. Quite so, but hardly the fault of the antenna and has nothing to do with any perceived characteristic. Why not make it in a rubber matrix and be about 2" * 4" folding up. That would be goog for added sensitivity I would strongly suspect. Paul Birke (EE) Hi Paul, Soothe your suspicions. A randomly crushed antenna is just as effective. However "just as effective" means equally in-effective. totojepast wrote: According to the July 1999 issue of Scientific American (available online at http://www.sciam.com/article.cfm?art...B7809EC588F2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? They could. Some manufacturers sell antennas complete with resistors for their own novel characteristics. Some cellphone users paste in a foil do-dad sold at two for $19.95 on TV too (never mind that a piece of aluminum foil works just as well for a penny's worth of material and no shipping/handling fee). "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) They could also claim to be 55% more efficient than a resistor too. Just why these fractal antennas work so well was answered in part in the March issue of the journal Fractals. Cohen and his colleague Robert Hohlfeld proved mathematically that for an antenna to work equally well at all frequencies, it must satisfy two criteria. It must be symmetrical about a point. And it must be self-similar, having the same basic appearance at every scale--that is, it has to be fractal." Others, who were not employed selling fractals have proven mathematically that they are not. Now, if you replace antennas with cigarettes and mathematics with reports on cancer, guess what clash of reports you would find there. A simple review into the quality of science of fractals "antenna research" reveals not very much range nor depth. Most announcements are repetition of unique examples that you will never find in that cellphone. As one poster pointed out YEARS ago, was that if fractals were such a good idea, we would all have replaced our antennas with them by now. This, of course, has lead one fractal proponent to simply declare that all the antennas we do use today, are already fractal! This oddball of recursive thought leads us to then ask, what merit is there in your particular kind? That's where you get into math 4 places to the right of the decimal for complex geometries that could only begin to make economic sense in the GHz frequencies (if you cared). Anyone could as easily make the same claims for the unique color of ink in their sales brochures giving boosted performance. 73's Richard Clark, KB7QHC |
This explains most clearly why MOT has been a bad investment since I quit in
'97. When I went there in '81 it was a good investment. We used to have perfect yields. Now the factories are shut. Fractal Geometry and Classical Electrodynamics have little to do with one another at HF. Or elsewhere. Mandelbrot's office door had one picture on it when I made my observation in '84: Gauss's. Buy a book. Drink bourbon; Do math. Die anyway. nite H. "Richard Clark" wrote in message ... On Sun, 07 Sep 2003 15:29:55 GMT, Paul Victor Birke wrote: This is a very good question!! Unfortunately for such a good question, the answer reveals a mediocre reality compared to the glowing claims. snip- http://www.sciam.com/article.cfm?art...-9EB7809EC588F 2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? They could. Some manufacturers sell antennas complete with resistors for their own novel characteristics. Some cellphone users paste in a foil do-dad sold at two for $19.95 on TV too (never mind that a piece of aluminum foil works just as well for a penny's worth of material and no shipping/handling fee). "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) They could also claim to be 55% more efficient than a resistor too. snip- Anyone could as easily make the same claims for the unique color of ink in their sales brochures giving boosted performance. 73's Richard Clark, KB7QHC |
Richard Clark wrote: Proximity often leads to increasing loss, and rarely opportunity for boundless gain. I was thinking only of more sustainable gain, certainly not boundless!! They have them stuck inside the unit and you have your hand wrapped around the antenna-not such a good idea since you are conducting, at least partially, and therefore shielding the inside antenna. Quite so, but hardly the fault of the antenna and has nothing to do with any perceived characteristic. Indeed but not a clever design idea wrt antenna placement was my point. Why not make it in a rubber matrix and be about 2" * 4" folding up. That would be goog for added sensitivity I would strongly suspect. Paul Birke (EE) Hi Paul, Soothe your suspicions. A randomly crushed antenna is just as effective. However "just as effective" means equally in-effective. Ouch! As one poster pointed out YEARS ago, was that if fractals were such a good idea, we would all have replaced our antennas with them by now. Yes well that would be the case except maybe for Patent monies. all the best Paul |
I think that the tree antenna in:
http://www.josechu.com/moving_fractal/index.htm would be good for cellphones, provided that the length of the (horizontal or vertical) branches is a fraction of the wavelength. Take into account that a grandson branch has exactly half the length of its grandfather's length. Josechu "totojepast" wrote in message om... According to the July 1999 issue of Scientific American (available online at http://www.sciam.com/article.cfm?art...B7809EC588F2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) Just why these fractal antennas work so well was answered in part in the March issue of the journal Fractals. Cohen and his colleague Robert Hohlfeld proved mathematically that for an antenna to work equally well at all frequencies, it must satisfy two criteria. It must be symmetrical about a point. And it must be self-similar, having the same basic appearance at every scale--that is, it has to be fractal." |
Dear Josechu
I saw these about a year ago. How well do they work? How well could they work wrt to gain sensitivity which I have just noticed in a cottage situation where reception was most borderline and involved location phone in a unique spatial vector postion. Would this antenna somehow be better in this situation re short whip. BTW I think there is a US patent on these, yes? Josechu wrote: I think that the tree antenna in: http://www.josechu.com/moving_fractal/index.htm would be good for cellphones, provided that the length of the (horizontal or vertical) branches is a fraction of the wavelength. Take into account that a grandson branch has exactly half the length of its grandfather's length. Josechu "totojepast" wrote in message om... According to the July 1999 issue of Scientific American (available online at http://www.sciam.com/article.cfm?art...B7809EC588F2D7), Motorola started using the fractal antennas inside its cellphones. Do they still use them? And what about the other manufacturers? "(....) Cohen, who founded Fractal Antenna Systems four years ago, is now working with T&M Antennas, which makes cellular phone antennas for Motorola. T&M engineer John Chenoweth says that the fractal antennas are 25 percent more efficient than the rubbery "stubby" found on most phones. (...) Just why these fractal antennas work so well was answered in part in the March issue of the journal Fractals. Cohen and his colleague Robert Hohlfeld proved mathematically that for an antenna to work equally well at all frequencies, it must satisfy two criteria. It must be symmetrical about a point. And it must be self-similar, having the same basic appearance at every scale--that is, it has to be fractal." |
On Sun, 7 Sep 2003 23:58:30 +0200, "Josechu"
wrote: I think that the tree antenna in: http://www.josechu.com/moving_fractal/index.htm would be good for cellphones, provided that the length of the (horizontal or vertical) branches is a fraction of the wavelength. Take into account that a grandson branch has exactly half the length of its grandfather's length. Josechu Hi OM, Combining a fractal form and scaling it to "a fraction of a/the wavelength" has no inherent correlation to suitability of application. There is no fundamental relationship between the physics of gain of an antenna and any fractal expression drawn out of a hat (or even one chosen deliberately with a sophisticated guess). Your example is visually pretty, but that counts for nothing compared to crafted random path antennas in the hands of a practitioner of the art of antenna design. The only way to determine if any particular fractal is suitable, is to test it against a standard. Few fractals pass this first cut. Worse yet, no small fractals exhibit any gain beyond that of the conventional dipole and rarely exhibit more gain than a small dipole. Physical orientation is another factor if there is gain above and beyond comparison to a small dipole (which includes a loop form by the way). Fractals do not exhibit radiation patterns that are intuitive from their shape (a dipole's best characteristics are broadside, a fractal could be off at a skew - if you could first guess what the major axis was). Let's just cut to the chase and let me point out the poor performance that fractals exhibit, specifically one of the best fractal examples from the owner of Fractal Antenna Systems compared to six designs that trounced it here in this group in open competition. These six designs have yet to be surpassed by any product from FAS. One might say that the pretty boy was pounded into the ground by six ugly sticks. 73's Richard Clark, KB7QHC |
Richard Clark wrote:
"These six designs have yet to be surpassed by any product from FAS." Maybe that`s right. John Kraus and associates are not so dismissive of "Artistic Antennas" (Fractals) on page 772 of "Antennas For All Applications". The Kraus book does illustrate the more complicated impedance variations of Fractals as compared with a loop or a flat plate used as an antenna. Best regards, Richard Harrison, KB5WZI |
Um, if Kraus (and Marhefka) was not dismissive of Fractals, why name
the chapter "Artistic Antennas"? In my opinion, it was a polite dismissal. Please read Steve Best's excellent paper in the IEEE Antennas and Propagation magazine. It shows that Fractals have no particular advantage over non-fractal shapes of similar parameters. -Spencer Webb KW2S www.antennasys.com (and contributor to Kraus' Antennas 3rd. ed.) Hi Spence-- Always happy to hear from someone at another antenna company:-) May I thus quote you as saying that the intent of the authors and contributors was to dismiss fractal antennas? Steve Best's article : "A Discussion on the Significance of Geometry in Determining the Resonant Behavior of Fractal and other non-Euclidean Wire Antennas"; AP Magazine;45,3 (June 2003) does not show what you said. The statement is made in the magazine, but it is not shown to be so nor supported by the data. May I suggest that you monitor the web site: http://www.fractenna.com which will host a critique of the article. Indeed, I invite you to also host the critique on your web site if you wish. The editor of AP Magazine was also invited to publish the critique(when it comes out) and, indeed, it would make sense to publish any relevant reviewer reports with it. The timing of this availability will be decided by Steve's next publication, which is expected to be in the next few weeks. Thank you for the opportunity to correct information and post a relevant source for info on this public forum. 73, Chip N1IR |
Roy Lewallen wrote:
I strongly endorse that caution. A couple of years ago, Chip (Dr. Nathan Cothen) of Fractenna . . . That's Cohen, not Cothen. I apologize for the typo. And while his posting address is , he's an officer of Fractal Antenna Systems, Inc., and often acts on their behalf. Roy Lewallen, W7EL |
I strongly endorse that caution. A couple of years ago, Chip (Dr. Nathan
Cothen) of Fractenna posted a "$1000 Challenge", offering $1000 for a design that could better his fractal design in specific properties he specified. Steve Best produced several, along with EZNEC models, which I posted on my web site. (They're still there -- you can download them from ftp://eznec.com/pub/MI2/.) The result was a long series of threats by Chip/Cohen, and postings on numerous newsgroups and private groups accusing me of piracy and theft of intellectual property. I wouldn't take Chip up on any offer without great caution. At least go to groups.google.com and see how this now-calm and rational sounding individual has reacted in the past to anyone who dares to publicly suggest that fractal antennas just might not be the best thing since canned beer. Roy Lewallen, W7EL Robert Hohlfeld won that challenge, Mr. Lewallen. It was not a "couple of years ago". This and other information is available on google as you state. It is also apparent from such postings that Steve Best did not enter the challenge. Indeed, Steve's loop(s) weren't anywhere near the best, even if they had been submitted. Best did not enter and did not win. For the FOM chosen, there are certainly better loops--fractal loops--than MI2, which was the entire point of the challenge. That is also a matter which is archived. The challenge has obviously succeeded in firing such investigations, which means that 'I had impact' as they say. Nothing pleases me more. The MI2 antenna is a very useful one in some applications. It has helped inspire a breakthrough approach to antenna optimization, which Bob Hohlfeld has championed, based upon some earlier (published) work by me in 1996/1997. The system incorporates genetic algorithms; fractal coding; and a supercomputer (grid) cluster made of off the shelf PC's. You and othersmay find a description of the system at: http://www.fractenna.com under the FRAGO system. The FRAGO system is working on a daily basis on antenna optimization, successfully I might add. It has assessed over 2 million antennas a month. It has also been described in several publications and conferences; indeed it will be described at one this coming week. With regards to the statements you have made above: In October, 2001 you had an attorney send me a letter of complaint for defamation and issued a demand of $50,000--based upon an alleged loss. You had counsel claim that such damages were suffered from my statements regarding ownership of copyright. You threatened to sue myself; Fractal Antenna Systems,Inc.; Boston University; and others. Certain matters regarding a potential counterclaim(s) were tendered to your counsel, and compelling evidence regarding ownership of copyright files was also provided. Incidentally, you did not provide any evidence of damages. Regarding MI2: Steve Best has recently published an interesting paper--as you know--and I am quite certain there are many here who will benefit from my corrections of factual error; omissions of citation; and so on; which will be presented in due time. A very brief summary: Steve's paper confirms my statement that the Small Loop Approximation is incorrect (at least for the regimes of antennas being considered); Steve has shown other fractal loops that share the very high (over 90%) efficiency and dipole gain; and so on, thereby corroborating the advantage of fractal in loops of that size and need. Clearly I see no issue, Mr. Lewallen, with you or anyone else discussing fractal antennas or any other sort of antenna. In fact, I never have. I presume, however, that accuracy and fact are also of some merit in the enterprise, and I invite you to strive for that; along with me and everyone else, in future discussions. With Best wishes to all, Chip N1IR |
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Such is the "science" of fractal electromagnetics. Such is the "legitimacy" of patents published. 73's Richard Clark, KB7QHC Paint it brown, add the claim that it is faster than light, and you got another "winner" or sucker? Wonder if somebody would repay the treatment and actually sue the clowns for misleading claims or advertising. If Art got patent for reflecting directors, then looks like anyone can get patent for anything and then rattle it in the face of ignoramuses. BYm BUm |
Can you please tell us what happened to the 10meter amateur band fractal
antenna design that was on your web site? We would appreciate it being put back if possible as I had not got around to building one before you took it off. Michael "Fractenna" wrote in message ... May I suggest that you monitor the web site: http://www.fractenna.com 73, Chip N1IR |
On Sun, 21 Sep 2003 11:10:09 GMT, "Michael Hart"
wrote: Can you please tell us what happened to the 10meter amateur band fractal antenna design that was on your web site? We would appreciate it being put back if possible as I had not got around to building one before you took it off. Michael Hi Michael, Two words of caution. 1. DO NOT ASK WHY. 2. Do not ask here. Either constitutes the most fruitless appeal offered in this forum. Approach him directly and ask for only what you want without comment, color, or explanation. Failure to observe protocol will invariably lead to difficult correspondence, unless of course you approach on your knees with hands clasped and raised (a few "hosannas" might be appreciated too). ;-) To date (for 4 years?), absolutely no other such plea has been fulfilled. There have been absolutely no reports of any successful constructions of this design (although it is not particularly difficult once you do some preparation). 73's & Good luck, write when you have one warming the air, Richard Clark, KB7QHC |
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