Antenna Toolbox is a new product in the MathWorks suite. In the 15b version of Antenna Toolbox, we have an object called customAntennaMesh. In this object you can pass a planar mesh and then solve the mesh as an antenna.
If you already have your fractal structure, mesh it and import it into Antenna Toolbox using the customPlanarMesh object. For more information look at the following examples
https://www.mathworks.com/examples/aa/category/modeling-custom-antenna
