  As a promising technology in beyond-5G (B5G) and 6G, dual-function
radar-communication (DFRC) aims to ensure both radar sensing and communication
on a single integrated platform with unified signaling schemes. To achieve
accurate sensing and reliable communication, large-scale arrays are anticipated
to be implemented in such systems, which brings out the prominent issues on
hardware cost and power consumption. To address these issues, hybrid
beamforming (HBF), beyond its successful deployment in communication-only
systems, could be a promising approach in the emerging DFRC ones. In this
article, we investigate the development of the HBF techniques on the DFRC
system in a self-contained manner. Specifically, we first introduce the basics
of the HBF based DFRC system, where the system model and different receive
modes are discussed with focus. Then we illustrate the corresponding design
principles, which span from the performance metrics and optimization
formulations to the design approaches and our preliminary results. Finally,
potential extension and key research opportunities, such as the combination
with the reconfigurable intelligent surface, are discussed concisely.
