High performance terahertz antennas based on split ring resonator and thin wire metamaterial structures

In this letter, the left-handed metamaterial (LH-MTM) which has a negative refractive index (NRI) is employed to improve the performance of microstrip patch antenna. The LH-MTM used in this work is a 3-D periodic structure which consists of split ring resonators and thin wires (SRR/TW). The LH-MTM is placed in front of the microstrip patch antenna and due to the negative refractive index property of the LH-MTM; the radiated electromagnetic beam size reduces which results in a highly focused beam. The proposed antenna has been designed and simulated using CST microwave studio and the MTM effective parameters are extracted from the s parameters by using Nicolson-Ross-Weir (NRW) algorithm. A parametric analysis has been performed to study the effects of the patch antenna and LT-MTM lens separation and the size of the 3-D LH-MTM structure on the radiating properties and the impedance matching of the proposed antenna. For the experimental verification, the proposed antenna operating at 10 GHz is fabricate, the return loss and the gain for the proposed antenna with and without MTM are measured. Furthermore, the results show the antenna gain improved by 1.5 dB which validate the concept of beam focusing using NRI MTM structure, while the return loss and the bandwidth are slightly reduced. However, the idea has been extended to the terahertz frequency range by designing and simulating a 303 GHz antenna for Heartbeat Rate (HR) measurement. For 303 GHz patch antenna, the results demonstrate an improvement in the gain by 1.1 dB, in the bandwidth by 14.73 GHz, and in the return loss by 12.62 dB over their original values without MTM lens, while the beam size is slightly reduced. The simulation and experimental results investigated the idea of the beam focusing using NRI MTM for wide frequency ranges including microwaves and terahertz.