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 3D 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 NRI 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 3D 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 fabricated, 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. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:382–389, 2016

In this paper, the left-handed metamaterial which acts as a lens is employed to improve the performance of a microstrip patch antenna. The left-handed metamaterial used in this work is a three-dimensional periodic structure which consists of circular split ring resonators and thin wires. The three-dimensional periodic metamaterial structure shows angular independency characteristics in wide range angles, so it acts as a metamaterial lens. However, the MTM structure infinite periodicity truncation has no impacts on the MTM lens scattering, effective parameters and homogeneity. The lefthanded metamaterial is placed in front of the microstrip patch antenna and due to the negative refractive index property of the left-handed metamaterial; the radiated electromagnetic beam size decreases which results in a highly focused beam. The proposed antenna has been designed and simulated using CST microwave studio, and the metamaterial effective parameters are extracted from the S parameters by using Nicolson-Ross-Weir algorithm and by selecting the appropriate ambiguity branch parameter. Furthermore, the angular independency of the metamaterial lens has been verified by rotating the metamaterial structure with respect to the excitation probe of the transverse electromagnetic waves and extracting the S-parameters and the effective parameters for each rotation angle. A parametric analysis has been performed to study the effects of the patch antenna and left-handed metamaterial lens separation and the size of the three-dimensional left-handed metamaterial 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 fabricated; the return loss, radiation pattern and gain for the proposed antenna with and without metamaterial are measured. Furthermore, the results show that the antenna gain is improved by 4.6 dB which validates the concept of beam focusing using negative refractive index metamaterial structure, while the return loss and bandwidth are slightly reduced. The simulation and experiment investigated the idea of the beam focusing using negative refractive index metamaterial lens in microwave regime.

In this paper, three dimensional periodic structure composed of circular split ring resonators and thin wires is used to improve the performance of a microstrip patch antenna. The three dimensional periodic structure is placed at the top of the patch within a specific separation distance to construct the proposed antenna. The radiated electromagnetic waves intensity of the proposed antenna is improved compared with the conventional patch antenna due to the electric and magnetic coupling enhancements. These enhancements occur between the patch and the periodic structure resonators and between the different resonator pairs of the periodic structure. As a result, the electric and the magnetic fields at the top of the patch are improved, the radiated electromagnetic beam size reduces which results in a highly focused beam and hence the antenna directivity and gain are improved, while the beam are is reduced. The proposed antenna has been designed and simulated using CST microwave studio at 10 GHz. An infinite two dimensional periodicity unit cell of circular split ring resonator and thin wire is designed to resonate at a 10 GHz and simulated in CST software, the scattering parameters are extracted, the results showed that the infinite periodicity two dimensional structure has a pass band frequency response of good transmission and reflection characteristics around 10 GHz. The infinite periodicity of the two dimensional periodic structure is then truncated and multi layers of such truncated structure is used to construct a three dimensional periodic structure. A parametric analysis has been performed on the proposed antenna incorporated with the three dimensional periodic structure. The impacts of the separation distance between the patch and three dimensional periodic structures and the size of the three dimensional periodic structure on the radiation and impedance matching parameters of the proposed antenna are studied. For experimental verification, the proposed antenna operating at 10 GHz is fabricated; the return loss and the gain for the proposed antenna with and without metamaterial are measured. Furthermore, the results show that, the antenna gain is improved by 4.6 dB while the beam width is reduced from 75 degrees to 41 degrees which validate the concept of beam focusing using electromagnetic coupling between the patch and the three dimensional periodic structure and between the different unit cells of the periodic structure, and also the return loss is improved by-20 dB, while the bandwidth is slightly reduced. The simulation and experimental results investigated the idea of the beam focusing using electromagnetic coupling improvement based on three dimensional periodic structures of circular split ring resonators and thin wires in microwave regime.

Abstract-In this paper, a new high performance slotted waveguide antenna incorporated with negative refractive index metamaterial structure is proposed, designed and experimentally demonstrated. The metamaterial structure is constructed from a multilayer two-directional structure of electrically split ring resonator which exhibits negative refractive index in direction of the radiated wave propagation when it is placed in front of the slotted waveguide antenna. As a result, the radiation beams of the slotted waveguide antenna are focused in both E and H planes, and hence the directivity and the gain are improved, while the beam area is reduced. The proposed antenna and the metamaterial structure operating at 10 GHz are designed, optimized and numerically simulated by using CST software. The effective parameters of the eSRR structure are extracted by Nicolson Ross Weir (NRW) algorithm from the s-parameters. For experimental verification, a proposed antenna operating at 10 GHz is fabricated using both wet etching microwave integrated circuit technique (for the metamaterial structure) and milling technique (for the slotted waveguide antenna). The measurements are carried out in an anechoic chamber. The measured results show that the E plane gain of the proposed slotted waveguide antenna is improved from 6.5 dB to 11 dB as compared to the conventional slotted waveguide antenna. Also, the E plane beamwidth is reduced from 94.1 degrees to about 50 degrees. The antenna return loss and bandwidth are slightly changed. Furthermore, the proposed antenna offered easier fabrication processes with a high gain than the horn antenna, particularly if the proposed antenna is scaled down in dimensionality to work in the THz regime.

In this article, a high performance terahertz slotted waveguide antenna incorporated with three dimension anisotropic low epsilon medium (LEM) is proposed, designed and theoretically investigated. The LEM is constructed from multilayer two dimension structure of electrically split ring resonator (eSRR) metasurface which exhibits anisotropic LEM medium in direction of propagation when it is placed in front of the slotted waveguide antenna at optimum distance. As a result, the E‐plane radiation beam of the slotted waveguide antenna is focused, and hence the directivity and the gain are improved, while the beam area is reduced. The proposed antenna as well as the LEM structure operating at 303 GHz are designed, optimized, and numerically simulated by using CST software. The effective parameters of the eSRR structure are extracted by Nicolson Ross Weir algorithm from the S‐parameters. The simulated results showed that, the E‐plane gain of the proposed slotted waveguide antenna is improved from 6.7 to 10.1 dB compared with the conventional slotted waveguide antenna. In addition, the E‐plane beam width is reduced from 94.1° to about 47°. The antenna return loss and the bandwidth are slightly changed. Furthermore, the proposed THz antenna offered easier fabrication processes with a high gain if it is compared with the horn antenna of the same size.