  We address the design and optimization of real-world-suitable hybrid
precoders for multi-user wideband sub-terahertz (sub-THz) communications. We
note that the conventional fully connected true-time delay (TTD)-based
architecture is impractical because there is no room for the required large
number of analog signal combiners in the circuit board. Additionally, analog
signal combiners incur significant signal power loss. These limitations are
often overlooked in sub-THz research. To overcome these issues, we study a
non-overlapping subarray architecture that eliminates the need for analog
combiners. We extend the conventional single-user assumption by formulating an
optimization problem to maximize the minimum data rate for simultaneously
served users. This complex optimization problem is divided into two
sub-problems. The first sub-problem aims to ensure a fair subarray allocation
for all users and is solved via a continuous domain relaxation technique. The
second sub-problem deals with practical TTD device constraints on range and
resolution to maximize the subarray gain and is resolved by shifting to the
phase domain. Our simulation results highlight significant performance gain for
our real-world-ready TTD-based hybrid precoders.
