Piezoelectric Acoustic Identification Tags with Frequency Multiplexed Energy Harvesting and Backscatter Communication Operation for Underwater Applications
The oceans cover a majority of Earth’s surface, yet a vast proportion remains unexplored due to the enormous physical scale and technical complexities. Ocean exploration and mapping offer immense returns through improved shipping routes, renewable energy generation, and accurate ocean modeling for understanding Earth’s climate processes.
Autonomous Underwater Vehicles (AUVs) offer adaptability, compactness and power efficiency while minimizing human oversight, making them ideal for ocean exploration. However, AUV operations are limited by currently achievable underwater localization and navigation solutions; hence the development of low-cost and passive (i.e., operable without an active power supply) acoustic underwater markers (or tags) can provide accurate localization information to AUVs improving their situational awareness, especially when operating in small scales or confined missions.
This work presents an Acoustic Identification (AID) tag that can be powered wirelessly with ultrasonic power transfer from a remote acoustic source (e.g. mounted on an interrogating AUV) and provide localization information using backscatter communication. The AID tag harvests energy from the acoustic signal generated from the AUV and communicates by modulating the reflected signals from an embedded piezoelectric transducer.
As a feasibility demonstration, this work develops a scaled (range of ≈ 100mm) broadband AID tag prototype that achieves concurrent acoustic energy harvesting (tuned around 1.3 MHz) and backscatter communication (in wider frequency band 600 kHz and 800 kHz) using frequency domain multiplexing. This scaled AID tag achieves data rates up to 200 kbit/s using Amplitude and Frequency based modulation communication.
Next, a full-scale AID tag is developed for short-range AUV missions (≈ 10 m) that uses a lower frequency piezoelectric transducer tuned in the broadband ultrasonic range (200 kHz-500 kHz) to achieve highly efficient power transfer (source-to-tag electrical power efficiency of > 2% at 6 m), and concurrent high data rate and backscatter level communication (> 83.3 kbit/s, > 170 dB SPL at 5.5 m) with potential operating range ≈ 10 m based on analytical extrapolations. Experimental tests benchmarking performance sensitivity to source and tag misalignment are presented. Finally, experiments are proposed to demonstrate device suitability for AUV routing and navigation applications.