hi llololl!!
The uwb application spetrum is from 3.1 to 10.6GHz. At your simulated results of antenna gains, I could assumed in the higher band(7-10.6GHz) has no resonate mode exist. You can adds a short current path to generate a mode. Therefore, a wideband operating can be obtained.
It is tought to get UWB for impedance. It is even tougher to get UWB performance for patterns. For the particular antenna, the gain at (theta,phi)=(0,0) is ok below 7 GHz. There is a dip at 9 GHz at (0,0). The peak of the gain at 9 GHz is at other angles.