By Jof Enriquez
Follow me on Twitter @jofenriq
Dr. Nathan “Chip” Cohen, inventor of the fractal antenna and founder/CEO of Fractal Antenna Systems, recently received approval for a cloaking technology from the United States Patent and Trademark Office (USPTO). More specifically, he and his firm gained approval for a fractal cell-based deflective electromagnetic shielding technology that can make invisible a variety of objects, including satellites, rockets, towers, antennas, vehicles, ships, spacecraft, and even people.
Patent 9,847,583 incorporates contents of several previous applications referring to the company's deflective electromagnetic shielding technology. These describe the transfer of radiation by using close-packed arrangements of resonators having fractal shapes/fractal cells, with their tight formation allowing for the plasmonic transfer of energy between the fractal cells.
"Invention of the invisibility cloak, acknowledged by our earlier patent 8,253,639, was a watershed moment, creating a new field of applied science, Cohen said in a press release. "Deflection is brought about through our novel technology, including deflecting electromagnetic waves around an object, so that it remains invisible and undisturbed. That applied science is emerging with real applications, and our firm takes patented claim on invention of these applications."
Since inventing the fractal antenna in 1988 and founding Massachusetts-based Fractal Antenna Systems in 1995, Cohen has built up an IP portfolio of over a dozen approved patents and pending patents — on cloaking, deflectors and absorbers — using fractal resonator metamaterials and surface waves. The company demonstrated person-invisibility before a Radio Club of America audience in 2012.
Its newest approved patent refers to systems and techniques that provide "one or more surfaces that act or function as power transfer surfaces or structures for which at least a portion of the surface or structure includes or is composed of "fractal cells" (fractal shapes) (as antennas or resonators) placed sufficiently closed close together to one another (e.g., less than 1/20 wavelength) to produce substantial replication of current present in one fractal cell in an adjacent fractal cell. The size of the fractal cells can be adjusted based on or tailored to a desired wavelength or wavelength range of operation."
With regards to how the cloaking device handles backscattering, Cohen explains to ARRL that, “The incoming wave reflects off a boundary condition at the object. Its reflection is out of phase and phase-cancels with the incoming wave. Bye-bye, backscatter.”
Cloaking technologies focus on microwave and infrared wavelengths, since "Cloaking at visible light has limited needs. Camouflage and projection methods are easier and cheaper at making something disappear to the eye. But at radio and heat wavelengths, the cloaking technology is an important enabler," according to Cohen.