Dual-band omnidirectional circularly polarized antenna utilizing epsilon negative transmission line

Abstract

In this paper, a dual-band omnidirectional circularly polarized (CP) antenna is presented using 0 and +1 modes of epsilon negative (ENG) transmission line (TL). The antenna is based on the circular mushroom structure with curved branches. The CP antenna is a planar type and simply designed without 90 degree phase shifter and dual feeding structure. The measured average axial ratios at 0 and +1 mode in the azimuthal plane are 2.03 dB and 3.88 dB, respectively. The measured average left-hand (LH) CP gain and right-hand (RH) CP gain are -0.40 dBic at 0 mode and -0.66 dBic at +1 mode, respectively, in the azimuthal plane and these results show a good agreement with simulated data.