An Ultra Wideband (UWB) parabolic reflector horn antenna system is designed to cover frequency range from 2 GHz to 18 GHz. The feed structure is redesigned for the ridged horn antenna to overcome the problem of its radiation pattern deterioration at higher frequencies, thus the designed feed maintains a single main lobe in the direction of horn axis. Also, the modifications are made in the shape of ridges to achieve better voltage standing wave ratio (VSWR) over the whole frequency band. This new modified horn antenna is then used as a feed for a prime-fed parabolic reflector design. The radiation pattern of designed parabolic reflector is also not divided into four large side lobes and has a single main lobe. This study is investigated using reliable commercial 3D EM simulation software CST solvers based on both Multi-level Fast Multipole Method (MLFMM) and Finite Integration Technique (FIT). The simulations result in high gain, low side lobe level with a VSWR less than 2 over the entire frequency band. © 2012 IEEE.