A UWB antenna for X-band automotive applications

A back-to-back Vivaldi Antenna is here proposed for a novel Vehicle to Infrastructure (V2I) communication system in the X-band (8.5-11GHz). The antenna has to be compact and low-profile in order to be installed on the car's roof. To cover the entire operating band, an ultra wideband (UWB) Vivaldi antenna has been chosen. Since the antenna has to radiate both in front and rear car driving direction, an array of two Vivaldi antennas has been designed, in a back-to-back configuration. Moreover, to attenuate the field radiation in the transversal direction - so decreasing the multipath effect due to the presence of buildings - the two antennas are fed with out-of-phase currents by means of a wideband hybrid T-junction. Finally, to further reduce the overall antenna size, the presence of the metallic car roof can be exploited to split the antenna size in half.