In this paper, we study terahertz (THz) simultaneous wireless information and power transfer (SWIPT) systems. Since coherent information detection is challenging at THz frequencies and Schottky diodes are not usable for THz energy harvesting (EH), we employ unipolar amplitude shift keying (ASK) modulation at the transmitter (TX) and a resonant tunnelling diode (RTD)- based EH circuit at the receiver (RX) to extract both information and power from the received signal. However, the electrical properties of Schottky diodes and RTDs are different, and unlike EH receivers based on a single Schottky diode, an accurate closed-form EH model for RTD-based RXs is not available, yet. In this paper, we model the dependency of the instantaneous RX output power on the instantaneous received power by a non-linear piecewise function, whose parameters are adjusted to fit circuit simulation results. We formulate an optimization problem to maximize the mutual information between the TX and RX signals subject to constraints on the peak amplitude of the transmitted signal and the required average harvested power at the RX. Furthermore, we determine a feasibility condition for the formulated problem, and for high and low required average harvested powers, we derive the achievable information rate numerically and in closed form, respectively. Our simulation results highlight a tradeoff between the information rate and the average harvested power. Finally, we show that this tradeoff is determined by the peak amplitude of the transmitted signal and the maximum instantaneous harvested power for low and high received signal powers, respectively.

翻译：本文研究太赫兹（THz）频段下的同时无线信息与功率传输（SWIPT）系统。鉴于太赫兹频段相干信息检测存在挑战，且肖特基二极管不适用于太赫兹能量采集（EH），我们采用发射机（TX）端的单极性幅移键控（ASK）调制，以及接收机（RX）端基于谐振隧穿二极管（RTD）的EH电路，从接收信号中同时提取信息与功率。然而，肖特基二极管与RTD的电学特性存在差异，且与基于单个肖特基二极管的EH接收机不同，目前尚缺乏针对RTD型接收机的精确闭合形式EH模型。本文通过非线性分段函数描述瞬时接收功率与瞬时RX输出功率之间的依赖关系，并通过调整函数参数拟合电路仿真结果。我们构建了一个优化问题，在发射信号峰值幅度与RX所需平均采集功率的约束下，最大化TX与RX信号间的互信息。进而，我们确定了该问题的可行性条件，并针对高、低所需平均采集功率场景，分别以数值形式与闭合形式推导了可达信息速率。仿真结果揭示了信息速率与平均采集功率之间的折中关系。最后，我们证明该折中在低接收信号功率时由发射信号峰值幅度决定，在高接收信号功率时由最大瞬时采集功率决定。