5. Conclusions

In this chapter, we have reviewed our recent efforts in utilizing metasurface to enhance the gain of the conventional antenna. For reflected MS, we propose a novel single-layer unit cell to greatly widen the phase-steering range and use it to design an MS antenna which achieves a wide working band of 10–12.3 GHz. On this basis, we propose a bi-layer reflected MS to simultaneously enhance the gain and transform the linear polarization to circular polarization of the Vivaldi antenna. The new MS enhances the gain and decrease beam width of the antenna in a 3 dB axial ratio band of 9.12–10.2 GHz. While for transmitted MS, we not only try to widen the phase-tuning range but also struggle to maintain high transmissions. Two methods have been proposed in this chapter to design transmitted MS. One is based on multilayer stack and the other is using an element-group. Compared with the patch antenna, the gain enhancements at 10 GHz are 11.6 and 10 dB for the methods of multilayer stack and group-element, respectively. In addition, both of the aperture efficiencies have reached 30%. These above MS antennas not only open up a new route for the applications of focusing MSs in microwave band, but also afford an alternative for high-gain antennas.
