Important innovation and Amateur Radio: INVENTION OF THE FRACTAL ANTENNA

Interesting article (below) authored by Robert Colburn, IEEE History Center.

An idea developed by a radio amateur with far more communications applications then the title suggests.

Hope you enjoy it.

73, John, WØPV

WHY MOBILE PHONES CAN DO SO MANY THINGS: THE INVENTION OF THE FRACTAL ANTENNA

PHOTOS courtesy © Fractal Antenna Systems,Inc.


Satellite sandwich with fractal antenna metamaterial over solar cells

Mobile phones perform multiple tasks by transmitting and receiving on many different frequencies. For example, when the user first dials, there is a carrier frequency that the phone and the base station communicate with each other to set up the call, establish which cell tower the phone is in range of, and choose which frequency or frequencies to use for the call. Some mobile phone systems use frequency-shift keying, which means the zeros of the digital signal are sent on one frequency and the ones are sent on another. BlueTooth, WiFi, and other applications use yet more frequencies.

Prior to the late 1980s, this would have required mobile phones to use an antenna for each frequency. Mobile phones would have needed many different antennas sticking out, each sized according to wavelength. Instead, today’s mobile phones owe their sleek design in part to antennas whose shapes are determined by fractals.

In 1982, mathematician Benoit Mandelbrot published his influential book, The Fractal Geometry of Nature. Some of the earliest applications of fractals were in computer graphics. Mandelbrot gave a paper on the landscapes of an imaginary planet at the 99th Colloquium of the International Astronomical Union, held in Balaton, Hungary in June of 1987. Also giving a paper at the conference was IEEE member and radio astronomer Prof. Nathan Cohen of Boston University. Cohen was (is) a ham radio operator (W1YW) and Mandelbrot’s talk intrigued him. He wondered how an antenna shaped according to fractal geometry would work.

Cohen found that it worked very well. However, his then landlord had a strict policy about not attaching antennas to the building. Cohen was working with 2-meter FM, meaning that a conventional antenna would need to be about one meter, and thus quite visible. Having found that his fractal antennas could be made much smaller, Cohen made a fractal microstrip antenna out of aluminum foil, glue, and construction paper using the pagoda motif, and attached it to the railing of his apartment. It was about six inches square.


Scaled up example of an enhanced RCS road reflector for autonomous cars/roads.

Despite its diminutive size and looking more like a doily than an antenna, (as well as being up on the 27th floor), the landlord learned of its existence and cut it down while Cohen was at work, teaching a math class. Cohen found its sad remains in the snow on the ground below a few days later. Given that the antenna’s descendants now function in hundreds of millions of devices around the world, the severing of the prototype must surely rank as one of the most infelicitous acts of technological obstruction since the Visigoths dismantled the Roman aqueducts. In addition to their uses in mobile phones and computers, fractal antennas have important applications in RFIDs and in vehicular radar and collision-avoidance systems. They reduce scattering of the signal and enhance the radar reflection of highway tags. As one measure of fractal antennas’ importance, IEEE has published more than 2,100 papers on them.


Wideband fractal elements for a multisector MIMO array

“Fractal antennas not only shrink antenna sizes, but also control multiband performance, enable wideband use, and actually increase realized gain in small sizes. The gain attribute arises from being able to produce multiple current maxima, such as on a fractal perimeter, in a highly compact area. Constructive interference can happen in regimes far smaller than a ¼ wave,” Cohen explains.


Conductive ink on fabric for wideband antenna on garments

Fractal Antenna Systems, the company Cohen founded, filed U.S. patent 6,452,553 in August of 1995 for the fractal antenna. The earliest adopters of the technology were government customers. “Today,” notes Cohen, “you would be challenged to get an x-ray, use radios or phones in a public building, or fly on a commercial jet without fractal antennas. Fractals are a big part of keeping the world connected.”


Fractal antennas as metamaterial (showing insides) for far smaller replacement of Yagi-Uda antenna


2.4 GHZ metablade(TM) antenna and the Yagi-Uda it replaces.

In addition to being a very widely-used technology, fractal antennas are visually intricate and beautiful. Because they are small enough to be hidden inside the technologies that they make work, most of us are not aware of them. The author hopes that this article has raised their visibility.

 

As my wife pointed out, I am now an 'hysterical' figure...

But like the Monty Python sketch, 'I'm not dead yet'.

In order to prevent the previously heated exchanges on this subject--many competitor-driven-- I will take PM but will not provide responses on this thread.

I will, however, point out that every year I get a few other hams that want to write up articles on fractal antennas. I tell each and every one that I will check for accuracy but have no interest in co-authoring. Not one of them has gone beyond the 'puttering around ' stage. If you look back, you can even find some of that on QRZED on prior fractal thread from years ago.

So if you want to do something, that's fine: like everything else in life, the follow-through is the most important.

Also, PLEASE no more comments like:'If they worked then why don't I see articles in IEEE publications'. As if its MY responsibility to be the author and gatekeeper....

Colburn verified that there are over 2100 IEEE scholarly articles. There are about 4000+ or so or more world wide. Colburn was disappointed to see how few of them referenced the original inventor and paper(s)/patent(s) . This article was, in part, written by him to make it clear where it all began. It's his article: I only checked for facts and a quote, late in the game. Obviously I provided the photos, when asked

Some people have toyed with revisionist history on who invented fractal antenna elements. My priority is well established. The first paper was accepted for Comm Quart in April 1995 and pub'ed in Aug 1995. The patent was under the 'first to invent' system of the US PTO. It lists all the relevant prior art. I was first. So please: let's not turn this into a 'who invented radio' mud puddle.

Some wonder why I took so long to go from 1988 to publishing in 1995. The answer: others made it very challenging, and I had modest resources. My equipment was purchased at the MIT Flea markets . I had a dean that was not sympathetic to this work--even after publication-- and hinted I could lose my job. Not pleasant.

Frankly, because it was started in ham radio, it was considered pseudo science by many scientists. That hurt--a lot. I am proud to be a ham, so *&^&^them!

I have been out of academia for 20 years. I get frequent requests to re-join. The more I say no, the more requests I get. Human psychology is not logical.

Kids are now taught fractal antennas in grade school....either in their math class or 'STEM enrichment'.

That, is cool.

73
Chip W1YW

 

Well, ya did good, Chip.
There's an old saying - The best rebuttal when they say you are wrong is living well.

 

'Human Interest' header --Love it!

 

How much transmit power can the Metablade design handle? One advantage of a Yagi is that I can design it for 10-100 watt transmit power. In a receive-only application or in the context of an unlicensed device limited to a figure like 10 or 100 mW, the physical characteristics of a fractal antenna are less limiting.

Unfortunately one cannot access a datasheet on the FAS website without disclosing one's email address. It's a technique that other vendors use, but it's not a technique that encourages open exploration and discussion of the merits.

For the record, I have no reason to believe that fractal antennas are good or bad, nor do I have an economic interest either way.

 

That's why you have a throw away email address. Problem solved... explore away.

 

Will answer this one--please PM otherwise.

50W+ for 2.4 GHZ

Notta lot of voltage differential cell to cell because of the evanescent waves (generating surface waves).

Companies ask for emails because they want to track 'inbound'--not sell emails to someone else. Its typical these days for following up sales leads.

White paper coming out end of Sept/early Oct. And if you can wait, I have a book coming out...after COVID. 2022? 2023?

 

This has to be one of the finest articles I have ever seen on QRZ. TNX, 73 et al, Lanny, K4ULP

 

Anyone have this scaled up to 40 or 80M? Looks interesting.

 

Excellent read and it gives me a jump point for further investigation. It reminds me of what I have seen in the Starlink phased array patent. Thanks for posting!

 

Ground wise--Dishy McDish is a very interesting piece of hardware. Then again, its a super expensive array and is the reason, IMO, Starlink is so expensive to subscribe. It will unlikely fall in price; heaven forbid, IMO, you have to replace it.

I am a radio astronomer and my background is arrays BTW. I do a fair amount of array work.

73
Chip W1YW

 

It's my guess that these are somewhat disposable installations, and with cheaper rocketry, an upgrade just means a new launch/deployment cycle. The price basis won't change, but what's been created is an artificial radiological troposphere. Who needs HF for long distance DX when a sat relay can handle your >50MHz traffic for you?

 

The clever website sends a verification email to the purported address, with a click-to-continue link.

 

Welcome to the world of assisting potential customers.