This study investigates the capability of an omnidirectional monopole antenna in achieving a high gain pattern that can be used in the UWB applications covering the frequency range of 3.1-10.6 GHz. The gain of a co-planar fed reference antenna with a partial ground is enhanced by using two main techniques; incorporating the antenna with an enlarged ground plane and metal reflector plates in different configurations. The gain level of the reference antenna in the yz-plane (1.9-4.6 dBi) is enhanced up to a gain level of 9.25-14.8 dBi with the help of the two gain enhancement techniques. Furthermore, a minimum gain of 12 dBi with a maximum deviation of 3 dBi is observed over the 4.2-9.8 GHz frequency range. As a proof of concept, two configurations of the designed antennas are fabricated and tested.