difference between simulated and measurement results in UWB

Hi all,
I designed a UWB antenna and implemented on fr4 substrate, but my measurement result is not very good, what's happening? what's solution?
I uploaded my result.

thanks

You're joking, right?

to me its damn good!

biff44, why?! it's cheap

hi,
Is you simulate the gainand radiation pattern?
may be this result correct for s11 only
i think you should get better result for all the s11,gain,directivity and radiation pattern then you can measure and compar your results

Thank

Eng.M.hassanien

It IS cheap. But to be wondering why there is a small discrepancy between measured and predicted data at 10 GHz on an FR4 board is.....asking too much?