Dear danesh,
if you mean fractal wire antennas, they are well formulated, and either Dr. Best showed that some nonefractal shapes have better fractal specifications, such az miniaturization or logperiodic impedance behavior.
but, if you are interested in other fractal antennas, such as fractal microstrip antennas, I should say that they are really new, and the research is going on in this toppic, for example I find a new wideband miniaturized fractal antenna based on rectangular koch rectangle. meanwhile, the theory of fractal arrays is another nice topic, still growing, and very practical.
thus, please specify the kind of fractal antenna you are interested in, and then I can further guide you.