I am new to CST Studio Suite  . 
I am designing a folded dipole antenna and want to feed it using a coax cable.
So i tested the Folded dipole on its own using a discrete port to find its impedance and got it to be around 300 ohms
 

I have a coax cable of 75 ohms and want to match it with antenna using a 4:1 balun 

For that i have used a wavelength/2 coax.

I have basically made this structure with appropriate diameters. 
Since my target frequency is 60 Mhz my length of the bent section is around 1.25m on both sides.

So when i simulate it by connecting a resistance of 300 ohms as a lumped element across the the 2 terminals. 
When i see the s11 of the balun it is very bad.
s11 does not reach below 3db

and there seems to be no resonance

but when i simulate the same thing in cadence awr i get good results.

I get the normalized impedance close to 1. That means it converts 300 ohms to 75 ohms.

Can any of you help me with this. I can't seem to find what went wrong in this??