An implantable stimulation unit for multichannel functional electrical stimulation (FES) system applied to the restoration of motor functions has been developed. The stimulation unit implanted in the body is externally controlled and powered by an encoded carrier radio frequency of 1.23 MHz and a continuous frequency of 123 kHz, respectively. A new type of RF coil utilizing amorphous magnetic fibers was introduced to realize high efficiency of power transmission. Using this RF coil, electric power of 370 mW can be transmitted at an efficiency of about 55% at a coil space of 10 mm. The maximum power consumption of the implanted unit is about 300 mW, and the transmitter supplied with four cells of 1200 mAH Ni-Cd battery can operate continuously for more than 10 hours. The information is transmitted through a pair of twisted coil which prevents magnetic interference by power transmission frequency. Up to 16 independently controlled stimulus output channels are provided, with output channel selection and stimulus pulse amplitude controlled externally by the information transmitted in a packet style. The information to check operating states of the implanted unit is also returned. This bi-directional communication system can increases reliability and safety of the implantable FES system. Miniaturization of the implanted unit has been realized by using MCM (Multi-Chip-Module) for analog circuit and FPGA (Field Programmable Gate Array) for digital circuit, respectively. The size of the packaged unit is 50 mm x 65 mm x 11 mm.
|Number of pages||9|
|Journal||japanese journal of medical electronics and biological engineering|
|Publication status||Published - 1999|
ASJC Scopus subject areas
- Biomedical Engineering