Far-Field Acoustic Sensing Via pMUT-Based Subharmonic Tags: A Battery-Free Approach for Hybrid RF-Ultrasound Wireless Sensor Networks

We present an innovative class of piezoelectric–micromachined – ultrasonic – transducer (pMUT)-based Ultra-High-Frequency (UHF) subharmonic tags (SubHTs) for far-field sensing. The proposed system leverages the dynamics of a 20×20 36%-doped Scandium Aluminum Nitride (ScAlN) pMUT-array operating at 550 kHz and those of time-modulated circuit components to passively sense ultrasound from long distances with electromagnetic waves. By encoding the low-frequency response of pMUT array into the amplitudes of modulated electrical signals at the output of the SubHT, our research eliminates the need for batteries in acoustic wireless-sensor-nodes (WSNs). This approach significantly enhances the capabilities of WSNs based on acoustic transducers, opening exciting new opportunities for such WSNs in a plethora of applications.