Hybrid Mode Wideband Patch Antenna Loaded With a Planar Metamaterial Unit Cell

A wideband patch antenna loaded with a planar metamaterial unit cell is proposed. The metamaterial unit cell is composed of an interdigital capacitor and a complementary split-ring resonator (CSRR) slot. A dispersion analysis of the metamaterial unit cell reveals that an increase in series capacitance can decrease the half-wavelength resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, circulating current distributions around the CSRR slot with increased interdigital finger length bring about the TM 01 mode radiation, while the normal radiation mode is the TM 10 mode. Furthermore, the TM 01 mode can be combined with the TM 10 mode without a pattern distortion. The hybridization of the two modes yields a wideband property (6.8%) and a unique radiation pattern that is comparable with two independent dipole antennas positioned orthogonally. Also, the proposed antenna achieves high efficiency (96%) and reasonable gain (3.85 dBi), even though the electrical size of the antenna is only 0.24λ 0 ×0.24λ 0 ×0.02λ 0 .