A novel ultra-wideband (UWB) dielectric rod antenna fed by a planar structure is presented. The planar structure consists of a circular slot antenna supplied by a dipole. This planar antenna excites the HE11 mode of an attached circular dielectric rod. Due to this combination, a broadband and low-dispersive overall antenna performance is achieved. Furthermore, an additional reflector at the backside of the antenna increases the directivity. With this configuration, a return loss better than 10 dB from 3.5 to 11.8 GHz is achieved with a nearly constant gain and a mean gain of 8.7 dBi. Beside the standard characterization, the system performance of the antenna is evaluated by means of the fidelity factor calculated from time-domain measurements and applying a UWB impulse generator.