Combining Multiband Properties in Modified Sierpinski Bowtie Antennas

The Sierpinski fractal antenna, which exhibits log periodic behavior, is modified by replacing inner triangular elements with circular ones, up to two iterations. If the circular holes are kept separated, not exhibiting fully self-similar gap structure, then higher resonance periodic modes of the bowtie antenna are strengthened. If the circular holes are superimposed such that self-similar gap structure is exhibited, then a resonating mode appears at a frequency following the log periodic behavior. It is thereby found that, at least to a certain extent, the self-similar antenna behavior of the Sierpinski fractal can be combined with the periodic behavior of the solid bowtie to increase the number of performing frequency bands in a predictable fashion. The results were found both through simulations and experiments. The effects of a wide bandwidth balun versus direct connected bowtie dipoles were also measured and presented. Measurements using a wideband balun to decrease unwanted currents in balanced to unbalanced transmission lines normally improves field pattern response, while overall improvement was observed at lower frequencies, higher frequency improvement was negligible.