Bandwidth Enhancement of an Antipodal Vivaldi Antenna Facilitated by Double-Ridged Substrate-Integrated Waveguide

A printed antipodal Vivaldi antenna (AVA) fed with double-ridged substrate-integrated waveguide (DRSIW) realizing decreased cut-off frequency and increased bandwidth is proposed in this communication. DRSIW can achieve a much lower cut-off frequency compared with normal substrate-integrated waveguide (SIW) because of the inserted ridge. As the printed AVA has an intrinsically wide bandwidth, the DRSIW-fed printed AVA realizes a significantly decreased cut-off frequency and increased bandwidth compared with Vivaldi antennas fed by normal SIW. Consequently, the electrical dimensions at the cut-off frequency of the AVA fed by DRSIW are smaller than the AVA fed by normal SIW, and the miniaturization of the AVA is successfully realized. The design procedure of the proposed DRSIW-fed AVA is given in detail. To verify the feasibility of the proposed design, a prototype of a DRSIW-fed printed AVA is fabricated and measured. The bandwidth with $\vert \text{S}_{11}\vert \le -10$ dB ranges from 11.02 to 40 GHz, covering Ku-, K-, and Ka-bands. The gains are 2.15-5.75 dB within the operating band. The results show that the bandwidth of the printed AVA has been successfully increased by using the feed of DRSIW.