Please help! CST slotted bow tie patch antenna efficiency problems

Im a beginner in desperate need for help. I am designing a slotted bow tie patch antenna with a back coaxial feed which I have already created in CST. When a transient simulation is run, I get a practically non existant efficiency. When looking at the surface current, it appears that very little current is flowing on the patch surface. Where am I going wrong?

It would be greatly appreciated if you could look at my design and give me some advice and help.

many thanks.

http://dl.dropbox.com/u/52161018/slo...timpedance.zip