A Novel Method for Improving Antipodal Vivaldi Antenna Performance

Herein, a new method for improving the directivity and bandwidth of the antipodal Vivaldi antenna structure is presented. The method is based on introducing a parasitic elliptical patch in the flare aperture to enhance the field coupling between the arms and produce stronger radiation in the endfire direction. This approach improves the directivity without compromising the low frequency performance and removes the need for electrically thin dielectric substrates. The proposed antenna structure including the feeding line and transition measures $140 \times 66 \times 1.5 \text{mm}^3$ and has a peak gain $> 0\;{\text{dBi}}$ over the 2–32 GHz frequency range and ${>} 10\;{\text{dBi}}$ over the 6–21 GHz range, which is an improvement to what has been reported for Vivaldi antennas with similar size.