A novel structure based on ultra-wideband filtering circuit for isolation enhancement of Vivaldi antenna with narrow gap in H-plane

A novel structure based on ultra-wideband (UWB) filtering circuit for isolation enhancement of Vivaldi antenna with narrow gap in H-plane is proposed in this paper. An antipodal Vivaldi antenna array with series of parallel slots in feed arms and a reflective floor is adopted to gain lower profile height, higher front-to-back ratio (FBR), and better isolation in high frequencies compared to a conventional one. The proposed filtering decoupling structure (FDS), composed of three bow ties with slender serrated lines at the edges distributed on both sides of the dielectric plate, is not only located in the necessary path of the spatial coupling of the two units, but also electrically connected with the reflective floor to enhance the low-frequency decoupling effect. The measured results show that the decoupling antenna array work well in 1.8-12 GHz, and the isolation is improved by 24.1 dB at 3.2 GHz and 12.2 dB at 1.9 GHz with FDS. The proposed FDS works well from 1.6 to 4.7 GHz with bandwidth of 96.7%, and the minimum isolation in the operating frequency band is improved from 10 dB to 19 dB. Moreover, the radiation performance remains superior after decoupling. The proposed decoupling structure is potential in the application in large-scale UWB arrays.