A Miniaturized Tri-band Rhombus-Shaped Metamaterial-Inspired Antenna with Gain Enhancement using Complementary Closed Ring Resonators

In this study, a rhombus-shaped patch antenna is proposed using metamaterial transmission line. The motivation of this work is to overcome the problem of low gain while designing miniaturised antennas. The proposed design is based on coplanar waveguide feeding technique. A rhombus-shaped patch is chosen in this structure in which striplines are provided to connect the ground planes and to obtain the shunt inductance. Asymmetric meandered line inductors are integrated with the striplines for miniaturising the electrical size of the antenna. Further to improve the gain of the antenna in the lower bands, asymmetric ground plane and complementary closed ring resonator have been employed in the proposed structure. The electrical size of the proposed antenna is 0.168 λ ₀  × 0.151 λ ₀ corresponding to the physical size of 25 mm × 22.5 mm, where λ ₀  = free space wavelength at 2.02 GHz. Considering below −10 dB input reflection coefficient, this antenna operates in three bands covering 1.96–2.07, 4.06–4.72, and 6.43–7.79 GHz. In addition, the proposed antenna exhibits gain of 1.49, 2.68, 2.19, and 4.31 dB at 2.02, 4.48, 6.72, and 7.43 GHz, respectively, in the maximum direction of radiation.