Researchers at the University of California, Los Angeles, have plumbed the idea of using fractals—mathematical models of mountains, trees, and coastlines—to develop antennas for cell phones, automobiles, and mobile communications devices. Not only do such antennas present challenges due to their shrinking size, they also must be able to operate at different frequencies simultaneously. Wireless manufacturers in the automotive industry are seeking such an antenna for use in AM and FM radio operation, cellular communications, and navigation systems.
Fractals, short for fractional dimension, were originally used to measure jagged contours such as coastlines. These models can define curves and surfaces, independent of their scale. When any portion of the curve is enlarged, it appears identical to the entire curve, a property called self-symmetry.
Researchers discovered that the mathematical principles behind the repetition of these geometrical structures can be applied to an antenna design methodology. With fractal technology, more electrical length can be packed into smaller spaces, enabling the antennas to resonate at lower frequencies. And because fractal designs are self-symmetrical, they can be used to develop antennas that operate at several different frequencies.
Yahya Rahmat-Samii of UCLA's Henry Samueli School of Engineering and Applied Science is leading the fractal/antenna research effort. For further details, visit www.engineer.ucla.edu.