tlt with ferrite sleeve

I need to design and simulate a tlt 4:1 (made for instance in microstrip technology) with ferrite sleeve around the microstrip inn 40MHz-250MHz bandwidth. Anyone can help me? If i use ADS i could use the model XFERTL2 and i'd just need to know the inductance without the sleeve and effective dielectric constant of the coupled line, but i'd prefer to simulate the coupled lines (a short microstrip broadside coupler) with the electromagnetic simulator and then find something to simulate the ferrite sleeve around them.
thanks in advance