Metaline Application to Loop Antennas

First, this paper discusses two loop antennas; one is called the I-line loop antenna, made of a metamaterial I-line and the other is called the Γ-line loop antenna, made of a metamaterial Γ-line. The gain for a left-handed (LH) circularly polarized (CP) wave, G_LHCP, and that for a right-handed (RH) CP wave, G_RHCP, are revealed within a fast wave frequency region. Each loop antenna has a maximum value for G_LHCP at a low frequency and a maximum value for G_RHCP at a high frequency. The I-line loop antenna maximum G_LHCP is smaller than the maximum G_RHCP; conversely, the Γ-line loop antenna maximum G_LHCP is larger than the maximum G_RHCP. Second, a hybrid loop antenna made of the metamaterial I-line and Γ-line is analyzed. It is revealed that a maximum gain relationship of G_LHCP = G_RHCP can be obtained when the ratio of the lengths of the metamaterial I-line and Γ-line is appropriately chosen. The axial ratio and the VSWR are also discussed.