  Terahertz (THz) carrier frequencies (100 GHz to 10 THz) have been touted as a
source for unprecedented wireless connectivity and high-precision sensing,
courtesy of their wide bandwidth availability and small wavelengths, but
noteworthy implementation challenges remain to make this a reality. In this
paper, we survey recent advancements in THz technology and its role in future
6G wireless networks, with a particular emphasis on the 200-400 GHz frequency
range and the IEEE 802.15.3d standard. We provide a comprehensive overview of
THz systems, circuits, device technology, and antennas, while also highlighting
recent experimental demonstrations of THz technology. Throughout the paper, we
review the state-of-the-art and call attention to open problems, future
prospects, and areas of further improvement to fully realize the potential of
THz communication in next-generation wireless connectivity.
