In the late 1980s, American astrophysicist Nathan Cohen faced a domestic dilemma: his Boston landlord strictly forbade him from installing a bulky ham radio antenna on the building's roof. Far from giving up, Cohen decided to experiment with complex geometries to design a receiver that would fit on his windowsill without drawing attention.
Inspired by the mathematical theories of Benoît Mandelbrot, he took a piece of wire and meticulously bent it following the pattern of the Koch curve, a self-similar fractal shape that repeats the same design at infinitely smaller scales. When he connected the device to his radio equipment, the result was astonishing: not only did it work better than conventional antennas, but it picked up signals across a much broader range of frequencies.
This phenomenon is due to a unique mathematical property: by possessing a fractal structure, the antenna contains segments of multiple lengths within an extremely small physical space. Each fold resonates with a different electromagnetic wavelength, allowing for a compact multiband antenna without the need for external components.
In 1995, Cohen founded Fractal Antenna Systems. Today, this geometric technology is the invisible heart of our smartphones. Thanks to fractal antennas printed directly onto circuit boards, a modern cell phone can simultaneously manage 5G, Wi-Fi, Bluetooth, and GPS connections without needing to extend cumbersome telescopic antennas.
Source: IEEE Antennas and Propagation Magazine / Fractal Antenna Systems (Nathan Cohen)
