spiral antea in cst

I want to simulate a spiral antenna in CST?I have simualte it in HFSS10 but when i give seep of 2-18 GHz.it give ripples at end of sweep i,e after 15-18.Now checking in CSt.Can you send me a simple spiral antenna simlation in CST.which will be very helpful for me.Thanks.

Hi,
Macros --> Consruct --> Coils --> Linear Spiral Coil (or circular spiral or another, I don't know, what do you mean exactly)
Is it answer on your question ?
or easier: In help try write "Helix Antenna" :D

I mean circular spiral antenna

Hi,
You stated you have designed spiral in HFSS. I want to do the same but my option to draw spiral is not enabled?
Can you help?
Thanks in advance