Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation

• Published in: Ultrasonics Vol. 54; no. 7; pp. 1929 - 1937
• Main Authors: Ozeri, Shaul, Shmilovitz, Doron
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.09.2014
• Subjects: Acoustic Impedance Tests; Acoustics; Amplitude shift keying; Electric Power Supplies; Energy Transfer - physiology; Equipment Design; Humans; Impedance modulation; Miniaturization; Models, Theoretical; Prostheses and Implants; Skin Physiological Phenomena; Transducers; Transmission line model; Ultrasonic energy transfer; Ultrasonics - instrumentation; Transmission line model; Ultrasonic energy transfer; Amplitude shift keying; Impedance modulation
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2014.04.019

The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20mW to the implant.