Quasi-theoretical investigation of four circularly polarized metaloop antennas

Four metamaterial line loop (metaloop) antennas, RND-MTLP-C, RND-MTLP-N, SQR-MTLP-C, and SQR-MTLP-N are investigated to clarify the antenna characteristics. Each metaloop is made up of either a C-type metamaterial line or an N-type metamaterial line, where the dispersion characteristics of the unit cell for the C- and N-type metamaterial lines are designed to be as similar as possible. The RND-MTLP-C and SQR-MTLP-C act as a dual-band counter circularly polarized antenna across a fast wave frequency region. It is found that, depending on the deviation factor, the SQR-MTLP-N behaves as a tri-band circularly polarized antenna, but the RND-MTLP-N does not have the tri-band characteristic. The radiation pattern, gain, and input characteristic in terms of the VSWR for the four antennas are clarified.