Reconfigurable miniature three dimensional fractal tree antennas

When used as antenna elements, fractal tree structures can be designed to produce multiband characteristics or to achieve miniaturization. Dipole antennas that use fractal tree structures as end loads can achieve a resonant frequency lower than a standard dipole of comparable length. In addition, increasing the density of fractal tree end loads can significantly improve the miniaturization of such antennas. Two design examples are considered where these miniature fractal tree antennas are made reconfigurable by the introduction of strategically placed reactive loads or RF switches. The first design is a fractal dipole antenna that operates at several frequency bands by adding reactive loads in the tree structure. The second design considered is a reconfigurable miniature dipole antenna that achieves a 43% size reduction with respect to its conventional counterpart (i.e., a half-wave dipole for the lowest operating band) and has a tunable bandwidth of nearly 70%.