Time-efficient low power time/phase-reversal beamforming for the tracking of ultrasound implantable devices

Abstract

Ultrasound (US) has recently gained attention for powering and communication with implantable devices due to its short wavelength and low attenuation. However, beam mis-alignments cause a sharp decrease in the amount of transferred power and quality of communication. This work investigates a telemetry protocol that relies on the difference in the phase of the received backscattered signal to precisely focus the US on the implantable device and track it over time. The interrogation signal is generated by a linear phased array probe, and the receiver is a pre-charged collapse-mode Capacitive Micromachined Ultrasound Transducer (CMUT) connected to a load modulation circuit. Using the time/phase reversal tracking algorithm, the RX was located within 300 ms after the first modulation was detected. The ability of the algorithm to track the RX while it is moving was also tested, showing that it can reliably track it up to a speed of 1 mm/s.