Circularly Polarized Antennas Based on Metamaterial Transmission Lines

Abstract

Two types of circularly polarized (CP) antennas based on metamaterial transmission lines will be presented. First, a dual-band omnidirectional circularly polarized ( CP) antenna of epsilon negative (ENG) transmission lines (TLs) is introduced. The antenna is based on a circular mushroom structure with curved branches and designed without additional feeding parts for a 90 degrees phase difference between two orthogonal modes as well as additional radiators for dual-band operations. A left-hand CP (LHCP) and a right-hand CP (RHCP) are obtained at the zeroth and the first order resonance modes, respectively. Second, a circularly polarized (CP) antenna based on mu-negative (MNG) transmission lines (TLs) is presented. The antenna consists of two pairs of resonators for two orthogonal polarizations. The 90 degrees phase difference between them is achieved by detuning the corresponding resonance frequencies. The experimental results agree with the theoretical results.