Single-layer near-zero refractive index metamaterial lens based on non-complete periodic arrays

In this study, an electric inductive-capacitive (ELC) resonator with a refractive index of around 0.08+i0.08 at 5.8 GHz serves as the unit cell. Based on the ELC unit cell, together with the electromagnetic wave (EMW) single knife-edge diffraction model, a near-zero refractive index metamaterial (NZIM) lens with a non-complete periodic array and small dimension of 0.8λ₀ ² is proposed to weaken the blocking of feed source radiation, and bring more significant gain enhancement compared to that with a complete periodic array. To demonstrate the proposed lens performance, the lens-loaded antenna formed by the proposed NZIM lens and a rectangular microstrip patch antenna (MPA) operating at the center frequency of 5.8GHz is provided. The measured results show that the relative bandwidth (RBW) of the lens-loaded antenna is 9.83% (5.51-6.08 GHz), which is expanded by 3.6 times contrasted with that of MPA (2.75%). Moreover, the average and maximum gains enhancement of 4.77 dB and 6.88 dB are obtained. Due to improving the radiation characteristic, this work can be used to drive the application of MPAs in wireless communication systems.