A compact planar slot antenna is proposed and developed for ultra - wideband Applications. This antenna has compact size of 23 x 18 x 1.2 mm. It is fabricated with FR4 substrate and it is fed by Coplanar Waveguide. The antenna operating range of 3.05 GHz to 12.91 GHz was observed from the simulation using Finite Element Method (FEM) and 3.11 GHz to 12.46 GHz were achieved from Method of Moments (MoM) based IE3D Electromagnetic solver. Experiment was conducted to verify the above frequency range and 3.08 GHz to 10.86 GHz was noted. The RBF neural network was also trained to validate the above result in terms of return loss of the proposed antenna. The antenna has stable Omni directional pattern in E-plane and bi-directional radiation pattern in H-plane. The group delay of the antenna is less than one nano second in operating bandwidth.