Fractal Antennas

Antenna design is a very tricky problem. Common designs are sensitive to only a narrow range of frequencies, and are not efficient if they are smaller than a quarter of the wavelength. This is a problem for small, portable antennas, such as those on cellular phones.
Fractal antenna designs (see Hohlfeld and Cohen) can overcome some of these problems. Experiments have shown that antennas built with only a small number of iterations of a fractal process can exhibit sensitivity at several frequencies. As the number of iterations increases, the lowest frequency of the antenna gets lower, and additional higher frequencies are added. Also, fractal antennas can operate efficiently at one-quarter the size of more traditional designs. Properly harnessed, these features represent real advantages. Several companies already are using fractals for compact, multifrequency antennas in cellular phones and military communications hardware. Fractal Antenna Systems,, a company founded by Nathan Cohen, has built a Sierpinski carpet cellular phone antenna fitting inside the body of the phone, and the multifrequency aspect of the antenna will allow GPS to be incorporated in the phone. Other applications include compact, multifrequency wireless LAN and maritime antennas. Several Fractal Antenna System designs are shown below.