A HIGH-EFFICIENCY POWER AND DATA-TRANSMISSION SYSTEM FOR BIOMEDICAL IMPLANTED ELECTRONIC DEVICES

In biomedical engineering, inductive transcutaneous links can be used for power and data transfer between external systems and implanted ele ctronic devices. The development of a micro-telemeter having a signifi cant implantation depth needs a high-efficiency magnetic transcutaneou s link. This paper presents a new system, which uses a multi-frequency load network for transmitter coil based on the class E power amplifie r. At the carrier frequency used, the resistive load is influenced by the coupling of the coils and by the variation of the implant equivale nt resistance. Modulating this latter between two rails permits one to modulate the amplitude of the external transmitter current and then t o transmit internal data without the use of the classical implanted em itter design. Furthermore, the fact that the modulation index depends on the coupling factor, allows one to find the external coil's correct position using a position feedback loop. A complete study of the conc ept of digital data transmission by impedance modulation associated wi th a class E power amplifier is presented. Internal data transmission using this system yields a decrease of the internal electronic circuit ry bulk and constitutes a high-efficiency energizing device. A theoret ical investigation shows that the efficiency of the power transfer var ies between 44 and 75% within a wide range of implantation depths (20- 40 mm).