An ultrawideband tightly coupled antipodal Vivaldi antenna array for UHF-Ku band applications

Designing a tightly coupled antipodal Vivaldi antenna (TC-AVA) array is proposed in this paper. With increased capacitive coupling effects of the overlapped end portions of adjacent flare-arms of AVA elements, the bandwidth of the TC-AVA array is effectively broadened by decreasing the lowest frequency about 69.5% compared with the single isolated element. The simulated results show that the proposed TC-AVA array operates over 0.51-18GHz band (35.3:1 bandwidth) for VSWR<;3.5 and possesses stable radiation patterns and nearly constant group delay in most frequencies. It is an excellent candidate for UHF-Ku band ultra-fast data-links and direction finding systems.