Advancements in Low-Power Ultrasonic-based Wake-Up through Metal

Nowadays, increasing digitalization may give acoustic communication an essential role in areas where electromagnetic communication fails or can only be employed with extensive effort. Consequently, acoustic communication systems need to address the challenges of real-world applications. One key requirement are the limited energy resources that battery-powered sensor nodes possess. Besides the high energy consumption during transmission and reception, listening to the communication channel for synchronization between transmitter and receiver is a major energy consuming factor. For this purpose, we introduce a concept of wake-up receivers for acoustic communication systems, originally known from radio technology. Therefore, this contribution presents a concept of a low-power acoustic wakeup receiver implemented with a demonstrator through a 1.6 mm thick metal barrier. We exploit two fundamental resonance modes of a piezoelectric disc transducer to facilitate an acoustic wakeup. The radial vibration mode at 220 kHz enables frequency-based wake-up with a sensitivity of –87 dBm and a radial distance of 1.35 m. The thickness extension mode at 1.2 MHz generates a 100 kHz subcarrier to transmit an 8-bit Manchester-coded ID at 1.1 kbps, achieving a sensitivity of –37 dBm. Both wake-up schemes have been demonstrated to function reliably with an energy consumption of 14.3 µW.