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An Ultra-wideband Circularly Polarized Hemispherical Helical Antenna

In this paper, an ultra-wideband hemispherical helical antenna with a novel flake-like arms structure is proposed. The proposed hemispherical helical antenna has better impedance matching characteristics compared with the traditional hemispherical helical antenna. At the same time, a wideband balun is designed to match the designed antenna and coaxial connecter. By introducing resistance and absorbing materials, the axial ratio bandwidth and pattern bandwidth of the antenna are extremely widened. Simulated results show that the designed antenna has a VSWR of less than 2, an axial ratio of less than 3 dB and a gain of more than 2.5dB from 2 to 18 GHz.