Application Of Fractal Theory In Antenna Design

As the product of the intersecting of the fractal geometry and antenna technology, fractal-shaped wire antennas can increase the working band and reduce the size. Koch fractal wire antennas, Sierpinski fractal wire antennas and Minkowski fractal loops have been specifically analyzed to show their advantage in miniaturization of antenna and the design of multi-band antenna.Antenna arrays are designed by terdragon and terdragon-6. When the curves are properly placed in the Cartesian coordinate, iterative procedures can be used for quick calculating the radiation patterns. Both have the desirable property of low-side-lobe, also they have no grating lobes even when the minimum spacing between elements is increased to one-wavelength. First, as the number of iterating increases, the main lobe becomes narrower and narrower, the rolloff becomes rapider and rapider, and the side lobe becomes lower and lower. Second, as the spacing between the elements increases, these happen, too.Using the principle of fractal geometry in the design of multi-band antenna, we can synthesize a specified fractal radiation pattern to design frequency-reconfigurable multi-band antenna arrays. With this method, the width of the main-lobe, the side-lobe height can be flexibly changed. And in the given bands, no grating-lobe appears. Actually, the array can't be infinitely big, so we think of a band-switching scheme. New thinning algorithm is developed for arrays designed by this method. In order to prove the design method, a specified array based on the Kaiser window function are designed, and its radiation pattern are computed.