Design of monofocal and bifocal lenses by new method and their application in high-gain lens antenna based on chiral metamaterial

A new method is proposed to design monofocal and bifocal lenses with the function of polarisation conversion based on chiral metamaterial (CMM). The phase distribution of lenses can be calculated more precise by the new numerical simulation method compared to the hyperbolic principle. The complete 360° transmission phase coverage at 1° phase intervals can be achieved by using the metallic split ring resonator and its two deformation structures. Monofocal lens can be realised by the hyperbolic method at microwave frequencies, but it is difficult to realise bifocal lens. The bifocal lens can be easily designed by the new method proposed in this study. The monofocal and bifocal high-gain lens antennas are designed to verify the effectiveness of the new method. The performance of the single-patch lens antenna designed by the new method is improved especially for its axial ratio, compared with the performance of the one designed by hyperbolic principle. The simulation peak gains of the two lens antennas designed by the new method are 18.1 and 18.7 dB at 9 GHz, respectively. The CMM-based lens antennas are fabricated, and the measured results are in good agreement with the simulation results.