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영남의대학술지 Vol.24_No.2 Suppl. P.S472-480, Dec. 2007

Original Article

이식형 FES 시스템의 경피적 에너지 및 데이터 전송

A Transcutaneous Energy and Data Transmission for Implantable FES Devices

이준하
영남대학교 의과대학 생화학?분자생물학교실
책임저자:이준하, 대구광역시 남구 대명 5동 317-1, 영남대학교 의과대학 생화학?분자생물학교실
Tel: (053) 620-4543, Fax: (053) 629-1344
E-mail: jhrhee@yumail.ac.kr

December 30, 2007

Abstract

Background:Inductive coupling links are frequently used for powering of implanted devices for functional electrical stimulation (FES) and cochlear. They are used in applications where implanted batteries are not capable of supplying a sufficient amount of power over the time of implantation or where continuous data exchange with external components is necessary like in a leg pacemaker.
Materials and Methods:This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1 MHz, the transmitter coil has a diameter of 46 mm, and the implant coil is 46 mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes.
Results:We chose the range of coil spacing (2 to 30 mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency.
Conclusion:The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

Key Words: Functional electrical stimulation (FES), Implantable FES

References

1. Miller JA, Belanger G. Mussivand T. Develop- ment of an Autotouned Transcutaneous Energy Transfer System. ASAIO Journal 1993 July- Sept;39:706-10.

2. Thoma H, Gerner H, Holle J, Kluger P, Mayr W, Meister B, Schwanda G, Stohr H. The Phrenic Pacemaker. Substitution of Paralysed Functions in Tetraplegia. ASAIO Journal 1987 July-Sept;33(3):472-79.

3. IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, IEEE International Committee on Electroma- gnetic Safety. IEEE Std 2005;C95.1.

4. Atluri S, Ghovanloo M. Design of a wideband power-efficient inductive wireless link for implantable biomedical devices using multiple carries. in Proc 2nd International IEEE EMBS Conference on Neural Engineering, Arlington, USA 2005 Mar;533-37.

5. Zoubir H, Roland I, Jacques C. A high-efficiency power and data transmission system for biomedical implanted electronic devices. Meas Sci Technol 1996;7:192-201.

6. Sokal NO, Sokal A. Class E- A New Class of High-Efficiency Tuned single-Ended Switching Power Amplifiers. IEEE J Solid-State Circuits. 1975;10:168-76.

7. Raab FH. Idealized operation of the class E tuned power amplifier. IEEE Trans Circuits. 1977 Dec; Jul;25:725-35.

8. Zierhofer CM, Hochmair ES. High Efficiency Coupling-Insensitive Transcutaneous Power and Data Transmission Via an Inductive Link. IEEE Trans Biol Eng 1990 Jul;37(7):716-22.

9. Ziaie B, Nardin MD, Coghlan AR, Najafi K. A Single-Channel Implantable Microstimulator for Functional Neuromuscular Stimulation. IEEE Trans Biol Eng 1997 Oct;44(10):909-20.

10. Troyk PR, Schwan MA. Closed-loop class E transcutaneous power and data link for microimplants. IEEE Trans Biomed Eng 1992; 39:589-99.

11. Donaldson ND, Perkins TA. Analysis of Resonant Coupled Coils in the Design of Radio Frequency Transcutaneous Links. Med & Biol Eng & Computing 1983 Sept;21:612-27.

12. Flack FC, James ED, Schlapp DM. mutual inductance of air-cored coils: effect on design of radio frequency coupled implants. Med Biol Eng Comput 1971;9:79-85.

13. Hochmair ES. System optimization for improved accuracy in transcutaneous signal and power transmission. IEEE Trans Biomed Eng BME 1984;31:177-86.

14. Zierhofer CM, Hochmair ES. Geometric approach for coupling enhancement of magnetically coupled coils. IEEE Trans Bio Eng 1996 Jul;43(7): 708-14.