Antenna Beamwidth-Dependent Sub-THz Propagation Characteristics based on Indoor Measurements at 159 GHz

With a growing focus on the utilization of frequencies above 100 GHz, known as the sub-THz bands, for communications and radiowave indoor navigation, directional beamforming has also been actively discussed as an enabling technology. However, either omnidirectional or specific beamwidth propagation characteristics have been primarily reported, which may not be useful when employing different beamwidths for beamforming or directional antennas. In this paper, we investigate beamwidth-dependent path loss and delay spread based on analysis of measurement data collected in a typical indoor office environment at 159 GHz. We observed that path loss increases as the beamwidth narrows due to the spatial filtering effect. This is more pronounced under NLoS conditions, since the presence of a strong dominant MPC is not guaranteed unlike LoS. We also observed variations in RMS delay spread depending on the beamwidth. We believe that these beamwidth-dependent path loss and delay spread characteristics will be useful for coverage estimation and system protocol design when utilizing sub-THz bands with directional beamforming.