Multi-layer periodic surfaces and metasurfaces for high-gain antennas

Novel highly-directive Fabry-Perot (FP) type antennas with significantly enhanced bandwidth performance based on periodic metasurfaces are presented in this thesis. The proposed antennas are formed by multiple layers of periodic surfaces and metasurfaces placed over a ground plane and a low directivity primary source. Initially, multi-layer FP antennas of half wavelength air cavities are investigated as an effort to achieve broadband highly-directive response and generalize the concept of the directivity-bandwidth product enhancement by adding appropriately designed PRS layers in FP type antennas. Subsequently, the limitations of this technique are investigated by studying the dispersion characteristics of the modes supported in multi-layer FP LWAs, providing a full interpretation of the operation of multi-layer Fabry-Perot LWAs. Moreover, a new concept of designing sub-wavelength profile multi-layer FP antennas by replacing the conventional PRSs with optimized composite metasurfaces is proposed outperforming previous designs of the same profile. Finally, an FP antenna operating at sub-millimetre wave frequencies is designed and presented based on micromachined fully metalized SU8 at around 300GHz. An in-house fabrication process is employed for the implementation of a prototype and measurement results are also presented in this thesis. This work offers an interesting new solution for planar high-gain low cost antennas for such high frequencies