Sensing-Centric Energy-Efficient Hybrid Beamforming Design for Terahertz Integrated Sensing and Communications

In this paper, we study the sensing-centric energy-efficient hybrid beamforming (HBF) design for wideband terahertz (THz) integrated sensing and communications (ISAC) systems. To mitigate the spatial wideband effect and enhance energy efficiency (EE), a new sub-connected true-time delayers (TTDs)-based HBF architecture is introduced. We redefine a generalized metric, referred to as sensing-centric EE (SEE), for measuring “information per Joule” in radar-centric ISAC scenarios, such as smart healthcare and intelligent manufacturing. Our objective is to maximize SEE by optimizing the HBF, while satisfying the constraints of radar sensing mutual information (SMI), communication rate requirements, transmit power budget, and the hardware limitations of analog beamformers. To solve this non-convex problem, we develop an effective algorithm based on the penalty dual decomposition (PDD) framework combining the Dinkelbach, minorization-maximization (MM), successive convex approximation (SCA), and element-wise optimization methods. Simulation results illustrate that the proposed design can increase SEE by approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$40\%$</tex-math></inline-formula> compared to the benchmark scheme.