Endfire Gain Enhancement Enabled by a Modified Antipodal Vivaldi Antenna With Metamaterials

In this letter, an effective method to increase the radiation gain of a Vivaldi antenna is proposed. In the antenna design, tilted parallel slots are etched on both flared radiators to suppress unnecessary broadside radiation through resonance effect and direct the energy predominantly in the end-fire direction. To further reduce the half-power beam width and increase the endfire gain, symmetric double E-shaped metamaterial units are introduced and arranged in a certain order at the end of the antenna without increasing the size. Compared to the traditional Vivaldi antenna, the proposed end-fire antenna demonstrates significant gain enhancement, with peak and average gain enhancements of 3.1 dBi and 2.4 dBi, respectively, across the frequency range of $13\sim 20$ GHz. To validate the proposed design, a prototype is fabricated and measured, and the experimental results are in good agreement with the simulations. The antenna has good performances of high gain, high efficiency, and compact size, which may have great potential applications in various microwave wireless communication systems.