Design of a low profile Eleven antenna loaded with stepped substrates

In this paper, a low profile Eleven antenna loaded with stepped substrates is designed. Compared to the Eleven prototype antenna, its height decreases by 19%. The antenna consists of the radiation structure, stepped substrates and the ground plane. Among them, the radiation structure consists of two symmetrically placed dipole petals, which composed of four pair of log-periodic dipoles. The stepped substrates also have four pair of blocks and are used to improve the impedance matching characteristic and radiation performance. The simulation results show that the reflection coefficient in the bandwidth of 2.4-3.4GHz is better than -8dB and the gain is greater than 9.5dBi. The Eleven antenna has a stable beamwidth and high aperture efficiency greater than 71.47% over the frequency range.