Low Cross-Polarization Vivaldi Antenna Fed with CPW–Slotline Transition

In this paper the element of a wideband linearly polarized Vivaldi antenna array is considered. The element is made on a thin low permittivity substrate. To excite a tapered slot a transition from a coplanar waveguide with a wave impedance of 50 Ohms at the input to a symmetric slot line with a wave impedance of 100 Ohms is used, and this transition is located orthogonal to the radiation axis of the antenna at its very base. The result of this concept is an antenna array element with a height to width ratio of 1:1, bandwidth ratio of 2:1 and a low cross-polarization boresight gain compared to conventional antipodal Vivaldi antenna array element.