Wideband circularly polarized antenna based on Vivaldi antenna structure

This letter presents a novel wideband circularly polarized (CP) antenna based on two orthogonally placed Vivaldi antennas. The two antenna elements are excited by a power divider that splits an input signal into two signals with equal magnitude and orthogonal phase. Linear tapered microstrip feeding structure is designed to realize the impedance matching. The antenna shows a -10 dB impedance bandwidth of 89%, -3 dB R bandwidth (AR<;3 dB) of 91%, and the maximum realized gain is 11.6 dBi. Meanwhile, good radiation patterns are achieved with the X-polarization is 20 dB lower than Co-polarization across the operating bandwidth in the boresight direction.