A novel frequency-selective metamaterial with negative permittivity and permeability for improving directivity and gain of a helix antenna is presented in this paper. The proposed metamaterial is composed of two Z-shape resonators printed on opposite sides of a dielectric substrate. Two forms of multilayered cells are found to be suitable for antennas and waveguides applications. In addition, a new method of designing a metamaterial-based helix antenna is presented with high directivity and gain. A comparison on radiation properties is given between the conventional and the new metamaterial-based helix antennas. Two comparisons on radiation properties are performed: (1) the effect of proposed Z-structure on monopole, dipole, and helix antennas; (2) the effect of OE3, split-ring resonator (SRR), and proposed Z-structure unit cells on the performance of helix antennas. The results show improvement of parameters such as directivity, gain, and radiation power of the new metamaterial-based helix antenna. Therefore, the combination of Z-structure with the helix antenna shows the best performance.

关键词： Antenna efficiency,  Negative permittivity,  Negative permeability,  Helix antenna,  Metamaterial