Mutual Coupling Reduction for a UWB Coplanar Vivaldi Array by a Truncated and Corrugated Slot

This letter reports mutual coupling reduction in an ultrawideband coplanar Vivaldi array (CVA) by incorporating truncated and corrugated slot at the border between adjacent elements. An examination of CVAs shows that mutual coupling in the E-plane is more significant than in the H-plane. Subsequently, arrays using exponential and rectangular corrugated slot are compared with those without a slot structure through the simulation of a surface current distribution. A novel exponential corrugated truncated (ECT) structure is implemented to improve a mutual coupling performance, while maintaining or even improving copolar field patterns. The results of simulation and measurement indicate that mutual coupling and return loss performance can be improved by controlling the length of corrugated structure and the distance of the slot structure from the center of the Vivaldi's tapered slot. The CVA achieves bandwidth ratio of 5:1, i.e., from 2 to 10 GHz. The ECT-CVA structure reduces mutual coupling to below -20 dB in a large portion of the whole band, shows 3.9-10.2 dBi gain over the entire band, increases a sidelobe level performance at 4-9 GHz compared to the CVA without slot structure.