Fractal Antenna Systems, Inc., established by noted radio amateur and inventor Nathan Cohen, W1YW, continues to stretch technological boundaries of belief. In an August 15 news release, the firm confirmed the issuance of its newest patents that will enable the next generation of stealth-like invisibility and absorptive shielding. The technology has both commercial and military applications. The firm pioneered and invented invisibility cloaks and holds both the “source” patent (8,253,639) and the related comprehensive intellectual property portfolio. Recently issued patent 10,027,033 is a continuation of that state-of-the-art innovation. It discloses a novel means of turning invisibility cloaks on and off, by changing the characteristics of a boundary layer. 

“The person or sensor inside the cloak is thus no longer blind,” Cohen said. He explained that not being able to sense the outside has previously been the top impediment to the use of invisibility cloaks.

The newest patent (10,030,917) describes related technology, where electromagnetic energy is absorbed by fractal-based metamaterials. Called “fractal absorbers,” the innovation uses evanescent waves to divert such impinging energy off to the sides, where it is absorbed in a resistive layer. Previously, absorbers relied on the thickness, not the width, of materials to accomplish this. Now these very thin fractal absorbers accomplish the same result with dramatic reductions in thickness and weight.

Fractal absorbers have been known and recognized as important for many years, and Cohen minces no words in reminding where the technology originated — with ham radio. “Did you know they started with very modest circumstances on the ham bands with gear bought from the MIT ham radio flea market?” he asked. Cohen said he overcame a lot of negativity early on and now “hamming and fractals have led to a new evolution of the antenna art.” 

“It is outrageous and bizarre to see teams from China claiming invention of fractal absorbers,” he said. “They have received unusual attention for their alleged invention, under the premise of so-called ‘supermaterials.’” 

“I believe PRC obtained information on the fractal absorbers, a spinoff of cloaking, by illegal means without my knowledge, let alone assistance, via the internet eavesdropping of my email,” Cohen told ARRL. He said his firm’s new patent conclusively establishes fractal absorbers as an American invention that pre-dates anyone else’s claims. The latest technology was developed under intense secrecy. “We held it under wraps, waiting for this patent issuance,” he said. “The patent application was withheld from publication,” he said.

Cohen called it ironic that the Chinese “have unwittingly established credibility for our invention and its American uses. And, in my opinion, they are now very far behind in the game.”

Earlier this year, China announced that a state-owned and -operated laboratory in Shenzhen is mass producing so-called metamaterials that can function as invisibility cloaks and might be used to make military aircraft invisible or undetectable. The announcement did not disclose the function of the new materials, however.

Cohen sees a variety of commercial applications for fractal absorbers, whose broad bandwidths and ultra-thin form factor are especially sought. Demonstrations targeting specific applications will be completed this fall.

“Fractal antennas are ham grown,” Cohen said earlier this year in accepting Hamvention’s Technical Achievement Award. “I am proud to be a ham. You should be too.” — Thanks to Business Wire for some information