Modified design of the antipodal Vivaldi antenna

A modified Vivaldi antenna operating at a frequency range of 0.5 to 3 GHz with lower cut-off frequency and higher low frequency gain than the conventional one is proposed. A current choke structure composed of a set of rectangular gratings that etched on the Vivaldi antenna prototype was introduced in the improved antenna to achieve the purpose of reducing the cut-off frequency and increasing the gain at the low end of operating band. FDTD method was used in the current choke structure optimizing work. Measured results show that compared with a conventional Vivaldi antenna without the current choke structure, the cut off frequency and gain of this novel antenna at low frequency band is 130 MHz lower and about 3.1dB higher, respectively.