Simultaneous Ultrasonic Power Transfer and Depth Feedback for Active Medical Implants

Wireless power transfer allows the delivery of energy to locations where electric wires cannot reach; one of the applications of it is powering active medical implants. Ultrasonic power transfer (USPT) has the potential to deliver a promising power density due to higher regulation limit. This method also possesses the possibility of maintaining a relatively small device size due to the short wavelength of mechanical waves in the ultrasonic frequency band. Previous studies have successfully proved the idea of powering a low-power computing device through ultrasonic power link. This paper reports a USPT system with the ability of data transfer and position feedback. The USPT system consists of a wearable transmitter and an implanted receiver in this system both featured a $2 \times 2 \times 2 \mathrm{~mm}^{3}$ cubic piezoelectric transducer: The resonant frequency of the system was determined to be 750 kHz. When the transmitter was driven with $\pm 30 \mathrm{~V}$, the receiver produced a peak-to-peak output voltage of 120 mV when placed $1 \mathrm{~cm}$ away from the transmitter. To test the capability of data transfer and position feedback of this system, the transmitter was driven with a non-return-tozero (NRZ) pulse. The pulse could be detected with a driving voltage as low as $\pm 5 \mathrm{~V}$.