This paper studies the effect of a hybrid reflector on the radiation pattern of an ultra-wide band diamond dipole antenna. The cause of a split radiation pattern in the broadside direction appearing when using a uniform Artificial Magnetic Conductor (AMC) based reflector is investigated and is found to be due to destructive interference in broadside direction produced by surface currents localized in certain areas of the reflector. A hybrid reflector is then proposed to mitigate this problem by using both electrical and magnetic conductors. This solution enhances the gain in the broadside direction of the ultra-wide band antenna. A complete antenna with feeding system and hybrid reflector has been fabricated and measurement results are presented.