Sub-Terahertz Channel Sounder: Review and Future Challenges

Due to the large amount of unused and unexplored
spectrum resource, the so-called sub-Terahertz (sub-THz) frequency
bands from 100 to 300 GHz are seen as promising
bands for the next generation of wireless communication systems.
Channel modeling at sub-THz bands is essential for the
design and deployment of future wireless communication systems.
Channel measurement is a widely adopted method to obtain
the channel characteristics and to establish the mathematical
channel models. Channel measurements depend on the design
and construction of channel sounders. Thus, reliable channel
sounding techniques and accurate channel measurements are
required. In this paper, the requirements of an ideal channel
sounder are discussed and the main channel sounding techniques
are described for the sub-THz frequency bands. The state-ofthe-
art sub-THz channel sounders reported in the literature
and respective channel measurements are presented. Moreover,
a vector network analyzer (VNA) based channel sounder, which
supports frequency bands from 220 to 330 GHz is presented
and its performance capability and limitation are evaluated. This
paper also discussed the challenge and future outlook of the sub-
THz channel sounders and measurements.