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A High Gain Antipodal Vivaldi Antenna with Director and Metamaterial at 1-28 GHz

An extremely ultra-wideband (UWB) antipodal Vivaldi antenna with a high gain and excellent impedance matching is proposed. An elliptical-shaped director embedded in an exponentially tapered slot is employed to enhance the gain at the high frequency band, while a metamaterial inspired structure is employed to enhance the gain around center frequency band and the symmetry of radiation pattern at the low frequency band. Furthermore, two sets of rectangular slits are symmetrically embedded around the tapered slot to improve the impedance matching at the low frequency band. Based on this novel structure, an antipodal Vivaldi antenna with good impedance matching and a high gain over an extremely UWB band is successfully designed. The reflection coefficient is lower than -12 dB at 1-4.16 GHz and lower than -16 dB at 4.16-28 GHz. The gain is 4.9-11.6 dBi at 1-8 GHz and higher than 11.6 dBi at 8-28 GHz.