Ultra-Wideband Circularly Polarized Endfire Atenna Based on Vivaldi Antenna

In this paper we proposed a novel ultra-wideband planar endfire circularly polarized antenna based on Vivaldi antenna. The structure of the proposed antenna includes a unidirectional dielectric radiator (UDR) and a Vivaldi antenna surrounded by the UDR. The Vivaldi antenna is fed by a substrate integrated waveguide (SIW) mounted on a 0.025λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> substrate, while the UDR is fed by the Vivaldi antenna, which effectively enhances the vertically polarized (VP) radiation generated by the dielectric instead of the horizontally polarized (HP) radiation. This polarization-selective enhancement technology enables us to develop an ultra-wideband circularly polarized antenna based on a planar Vivaldi structure. The antenna has a -10 dB impedance bandwidth from 10.9 GHz to 18.6 GHz, a relative bandwidth of 52.2%, and a total width of 7.7 GHz; at the same time, the 3 dB axial ratio bandwidth is also 7.7 GHz, ranging from 13.3 GHz to 19 GHz, with a relative bandwidth of 35.3%.