A 1:1 balun can be made from two sections of transmission line. One is 3 lambda/4, the other is lambda/4. Of for a 4:1 balun, use a single section of transmission line of lambda/2 in length. You can Google these. If the frequency is too low to make transmission line practical, then a transformer on a ferrite can be used.
You did not ask about HFSS. I don't know if you are trying to simulate something in HFSS. In that case, I'd be interested in what you get, as this is something I did once think about, but decided it was too much effort to make the coax and link it back on itself.
Dave