A High-Gain Terahertz Metallic Modulated Metasurface Antenna With a Wide Gain Bandwidth

Electrically large modulated metasurface antennas (MMAs) possess advantages of simple feeding and absence of beam forming network, while achieving a high radiation gain. However, they suffer from limitation in the gain-bandwidth product. This paper introduces a technique to expand the bandwidth of gain by utilizing a polarization selective surface (PSS). The PSS can generate a more uniform phase distribution and almost identical polarized directions above the MMA to improve its radiation performance, including the realized gain, gain bandwidth, sidelobe level and cross-polarization level. Detailed analysis is presented and discussed. For experimental verification, a D-band metallic MMA loaded with a PSS is fabricated and measured. The proposed metallic MMA is manufactured by high-precision 3D-printed technique and metalized using the magnetron-sputtering gold coating. The measured maximum realized gain is 30.5 dBi at 131 GHz with a measured 3-dB gain bandwidth of 9% which approaches the theoretical limit found for such antennas. The proposed MMA shows potential superiorities for developing high gain and low-profile THz antennas, even with an operating frequency over 300 GHz.