Gain Enhancement of the Patch Antenna Using TSRR NRI Superstrate

This article presents a high gain patch antenna with negative refractive index (NRI) superstrate for the application of Radio frequency energy harvesting system. Triangular split ring resonators (TSRR)-strip line are used as a NRI superstrate to enhance the gain of the patch antenna. It is demonstrated that the proposed triangular split ring resonator (TSRR) structure metamaterial yields negative value of an effective refractive index that over the frequency range of 774 MHz to 974 MHz. The negative refractive index structure is applied as a superstrate to a microstrip patch antenna. The simulation results show that the gain is effectively improved by 2.326 dB (85.96 %) after the incorporation of negative refractive index metamaterial superstrate on to the conventional patch antenna. The results illustrated that the gain of the proposed antenna is enhanced over the desired frequency band 935 MHz to 960 MHz. The air gap between the antenna and superstrate was also studied by applying the theory of Fabry-Perot (F-P) resonant cavity to obtain the optimum air gap of 55 mm to achieve the maximum gain. The proposed antenna is also fabricated and tested, the measured results shown that have good agreement with the simulated results in term of S parameters and radiation characteristics. Keywords— Microstrip patch antenna; triangular split ring resonator; negative refractive index; radio frequency harvesting system; gain