Time-Modulated Dynamic Arrays for Integrated Communication and Sensing: A Review of Opportunities, System Considerations, and Challenges

Time-modulated arrays (TMAs) utilize time as an alternative beamforming method to augment existing analog/digital/hybrid wireless beamformers. The introduction of the time dimension in such dynamic antenna arrays may offer advantageous beamforming capabilities to emerging integrated sensing and communication (ISAC) applications, dramatically reducing the hardware complexity of their implementations. This article reviews the state-of-the-art TMAs, with an emphasis on those reported in integrated-circuit (IC) technologies, such as complementary metal–oxide–semiconductor (CMOS), for wireless applications. Starting with an analytical framework of TMAs, their operation and beamforming characteristics are analyzed for multiple periodic switching schemes, including the ON/OFF amplitude-modulation scheme, the continuously ON 0 /180 phase-modulation scheme, and the double switching scheme with even/odd-symmetry. Then, a survey of the main IC applications in which TMAs have been proposed is presented, including their ISAC applications in transmitter (TX) concurrent multibeam generation, re ective relays that support multibeam reception and transmission, spatiotemporal ltering that can be used for sensing, and receiver multiple-input-multiple-output (MIMO) using one-wire interface and enhancing physical layer security in wireless communication. Afterward, the performance characteristics of TMAs for both receiving and transmitting beamforming arrays are analyzed and compared with standard single-beam and multibeam phased arrays. Finally, the potential challenges of TMAs, including the fixed-angle nature of their beams and the generated harmonics impact especially for TX arrays, are discussed.