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
.