▎ 摘　　要

Terahertz (0.1-10 THz) band communication is envisioned as a key technology to satisfy the increasing demand for ultra-high-speed wireless links. In this paper, a 3-D end-to-end model in the THz band is developed that includes the graphenebased reflectarray antenna response and the 3-D multipath propagation phenomena. In particular, the architecture of a graphenebased reflectarray antenna is investigated, and the 3-D radiation pattern is modeled. Moreover, a 3-D THz channel model based on ray tracing techniques is developed as a superposition of the line-of-sight (LoS), reflected, and scattered paths. By using the developed end-to-end model, an in-depth analysis on the 3-D channel characteristics is carried out. Specifically, the gain at the main beam of the graphene-based reflectarray antenna is 18 dB, and the 3-dB beamwidths in the elevation and the azimuth planes are 7. and 10., respectively. The use of the reflectarray leads to a decrease of the delay spread from 1.23 to 0.099 ns, which suggests that the resulting coherence bandwidth reaches 2 GHz. Moreover, the root mean square (rms) angular spread in the elevation plane is less than 0.12., which is one tenth of that without beamforming. Furthermore, the wideband channel capacity at THz frequencies is characterized, which can be enhanced with a larger transmit power, a lower operating frequency, a larger bandwidth, and a higher beamforming gain. Finally, the beamforming gain enabled by the reflectarray antenna is compromised at the cost of the strict beam alignment, and the deviation needs to be smaller than 11.. The provided analysis and the channel physical parameters lay out the foundation and are particularly useful for realizing reliable and efficient ultra-high-speed wireless communications in the THz band.