A new approach to design a low profile dipole antenna backed by a Mushroom-like Electromagnetic Bandgap (EBG) surface

Abstract

Various electromagnetic bandgap (EBG) surfaces have been widely applied to enhance the radiation efficiency of low profile dipole antennas. Previous design approaches are primarily based on the reflection phase profile of the EBG surface, which is derived by a plane wave incidence. They need to be augmented since the reflection phase profiles don't account for the complex near field interaction between the EBG surface and dipole antenna. The work presented in this paper is partially an extension of our previous research on a low profile dipole antenna backed by a frequency selective surface (FSS) [S. Zhan et al., 2007]. That paper shows that when dipole antennas are resonant at a frequency band where a TM surface wave is suppressed but a TE surface wave is supported; without any modification, the dipole antenna could be flush mounted on the frequency selective surface and achieve a very good radiation efficiency. Further research finds that the same design approach is applicable to a mushroom-like high impedance EBG surface, which is shown in Fig. 1. In this paper, transmission properties of a TM and a TE surface wave on the EBG surface are measured by two monopole antennas. Their different effects to vary the antenna input impedance are discussed. A dipole antenna integrated with the EBG ground surface is built based on the new design approach. A two-port network analyzer is utilized to verify the improvement of radiation efficiency of the low profile dipole antenna.