A Compact Folded Air Patch Antenna with Low Cross-Polarization

Abstract

In this paper, a compact folded air patch antenna with low cross-polarization radiation is proposed. The air patch antenna is folded along the E-plane so that the size of the antenna is reduced by more than 50%. Additionally, the folded structure can introduce multiple vertical current components to cancel the parasitic cross-polarization radiation from the feeding probe, leading to a low cross-polarization level in the H-plane. A prototype antenna working in the 2.4 to 2.5 GHz ISM band is designed and measured. The simulated and measured results show good agreement. The measured maximum gain at 2.45 GHz is 8.2 dBi and the measured antenna efficiency is higher than 88%. The measured beam width of the cross polarization that is 15 dB lower than the co-polarization is more than 120°.