A 400-GHz High-Gain Quartz-Based Single Layered Folded Reflectarray Antenna for Terahertz Applications

Compact high-gain antennas are highly desired in the high-speed terahertz (THz) wireless system, especially for the space limited application, such as the high-speed inter link inside the high density wireless communication base station. To this end, a 400-GHz folded reflectarray (FRA) antenna with high gain, high aperture efficiency, and compact profile is proposed in this paper. It is composed of a feed source, a single-layered reflectarray using a lithography process on quartz, and a wire-grid polarizer implemented by the printed-circuit-board technology. A 3-D printed fixture is used to assemble all parts together. In order to design accurately the proposed antenna, the THz electromagnetic properties of the supporting dielectric materials are extracted by using a THz time-domain spectrometer system. Then, a single-layered phasing element, made up of a pair of orthogonally I-shaped structures with an open square ring, is proposed and designed based on the extracted material characteristics. Both phase compensation and polarization conversion can be realized by the proposed unit cell. A reflectarray is designed by using the proposed phasing element with the conventional array synthesizing theory, and a THz grid polarizer is designed with strips on a 0.127 mm Taconic TLY-5 substrate. The THz grid is placed in front of the THz feed and the reflectarray, which is fully reflective to the feed and transparent to the reflectarray. All components of the FRA antenna have been fabricated and assembled. Experiments show that the FRA prototype has a peak gain of 33.66 dBi at 400 GHz with an aperture efficiency of 33.65%, and a 3-dB gain bandwidth of 16% (357-421 GHz).