Simultaneous Terahertz Imaging with Information and Power Transfer
Open Access DepositedTerahertz (THz) band transmission has the potential to revolutionize future-generation wireless networks by jointly meeting the communication and non-communication demands of their connected devices. Recent advances in THz semiconductor technologies and antenna design enable millimeter-scale devices, which are often battery-limited. The localization of these mobile devices in future-generation wireless networks is of paramount significance for beamforming to overcome THz propagation loss. Consequently, prospective signal processing and waveform designing techniques with co-design architectures are emerging either for joint communication and sensing or for simultaneous information and power transfer. In this dissertation, the convergence of THz communication, radiative wireless power transfer, and 3D radar imaging in a future-generation wireless network is explored. A promising approach is proposed for Simultaneous THz Imaging with Information and Power Transfer (STIIPT) from a base station transceiver to a millimeter-scale battery-limited integrated receiver (IntRx). Leveraging the ultra-wide bandwidth in the THz band, a low-complexity customized On-Off Keying (cOOK) modulation scheme for STIIPT to rectenna-based IntRx is devised. The customization in terms of symbol length, corresponding to a probability of On-key transmission under transmit power constraints, is performed to maximize either information rate or harvested energy while generating a radar-like image to localize the IntRx acting as a target. This is achieved by first presenting the theoretical models for each of the radar imaging, wireless information transfer (WIT), and wireless power transfer (WPT) in the presence of a cOOK modulation scheme. These models are then validated by circuit simulations to demonstrate all three simultaneously: (a) imaging of the 3D space with continuous ranging, (b) THz communication with Gbps information rate and nanoseconds latency, and (c) efficient energy harvesting in the far-field region. Finally, the comparative performance of cOOK modulation and pulse position modulation schemes is analyzed for simultaneous wireless information and power transfer. Additionally, a prospective application to STIIPT is presented in operating a battery-limited nano-drone swarms in a future 6G network. By employing a return-to-zero on-off keying signal modulation scheme in the sub-THz band, joint power transfer and radar imaging (JPTRI) is performed while maintaining ultra-low latency communication to control the swarm operation. The theoretical results are corroborated by simulations that highlight the robustness of the JPTRI approach against the scalability of a battery-limited nano-drone swarm. In another application, a joint transmission of both power and waveforms is performed to implantable neurostimulators for patients with neurodegenerative disorders. By employing unmodulated and modulated pulse density schemes, high- and low-frequency waveforms for neuromonitoring and neuromodulation, respectively are designed while also providing constant average power to the nanorectenna-based closed-loop neurostimulator. Thus, the STIIPT framework presented in this dissertation enables the THz systems of future-generation wireless networks to be designed with key functionalities of imaging for localization and WPT for energy harvesting piggybacked on the THz communications.
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