Hamburg University of Technology, TUHH, Institute for Autonomous Cyber-Physical Systems, 21073 Hamburg, Germany.
Sensors (Basel). 2023 Mar 30;23(7):3617. doi: 10.3390/s23073617.
Sensors for industrial and structural health monitoring are often in shielded and hard-to-reach places. Acoustic wireless power transfer (WPT) and piezoelectric backscatter enable batteryless sensors in such scenarios. Although the low efficiency of WPT demands power-conserving sensor nodes, backscatter communication, which consumes near-zero power, has not yet been combined with WPT. This study reviews the available approaches to acoustic WPT and active and passive acoustic through-metal communication. We design a batteryless and backscattering tag prototype from commercially available components. Analysis of the prototypes reveals that low-power hardware poses additional challenges for communication, i.e., unstable and inaccurate oscillators. Therefore, we implement a software-defined receiver using digital phase-locked loops (DPLLs) to mitigate the effects of oscillator instability. We show that DPLLs enable reliable backscatter communication with inaccurate clocks using simulation and real-world measurements. Our prototype achieves communication at 2 kBs-1 over a distance of 3 m. Furthermore, during transmission, the prototype consumes less than 300 μW power. At the same time, over 4 mW of power is received through wireless transmission over a distance of 3 m with an efficiency of 2.8%.
用于工业和结构健康监测的传感器通常位于屏蔽且难以到达的地方。声无线功率传输 (WPT) 和压电背散射使这种情况下的无电池传感器成为可能。尽管 WPT 的低效率要求节能的传感器节点，但近零功耗的背散射通信尚未与 WPT 结合。本研究回顾了现有的声 WPT 以及主动和被动通过金属的声学通信方法。我们使用市售组件设计了一个无电池和背散射标签原型。对原型的分析表明，低功率硬件为通信带来了额外的挑战，即不稳定和不准确的振荡器。因此，我们使用数字锁相环 (DPLL) 实现了软件定义的接收器，以减轻振荡器不稳定的影响。我们通过仿真和实际测量表明，DPLL 可以使用不准确的时钟实现可靠的背散射通信。我们的原型在 3 m 的距离上以 2 kBs-1 的速度实现通信。此外，在传输过程中，原型消耗的功率小于 300 μW。同时，通过无线传输在 3 m 的距离上接收超过 4 mW 的功率，效率为 2.8%。
