Abstract: A high-gain antipodal Vivaldi antenna operating at the frequency range of 1. 6 GHz ~20 GHz is designed. Semi-elliptical patches are loaded at the left and right ends of the conventional antipodal Vivaldi antenna, so the VSWR characteristics at low frequency are improved, thus increasing the impedance bandwidth of the antenna. In order to effectively constrain the electric field in the direction of main axis radiation, a trapezoidal dielectric substrate is loaded in the direction of major axis, which can solve the gain peak offset problem and improve the gain value. The measured results show that the VSWR is smaller than 2 between 1. 6 GHz and 20 GHz, its gain is 1. 5 dB ~11. 1 dB. In addition, gain peak shifting at E-plane is significantly restrained, and it also has the advantages of good radiation direction, high gain, low cross-polarization ratio.