An autonomous electronics system for ultrasound energy transfer and passive communication

Ultrasound is a promising method for powering of implants. It allows to transfer energy in a focused way, which leads to high efficiency and allows reaching implants deeply embedded in tissue. In addition, ultrasound can be used for communication with implants. In the present work, we developed a system combining energy transfer with a passive communication scheme based on modulating the backscattered signal amplitude. Using a receive transducer of 5 mm in radius and a 2-element 16 mm transmit aperture, up to 7 mW could be transferred, which was enough to power an LED and a circuit allowing encoding the optical sensor readout (photocurrent) into the backscatter information. By means of load modulation, amplitude variations of the backscattered signal until 35% were possible.