Wireless implantable EMG sensing microsystem

This paper presents a wireless, subfascially implantable electromyogram (EMG) sensing microsystem design for intelligent myoelectric control of powered prostheses. The implantable system consists of two Pt-Ir epimysial EMG electrodes, a custom-designed ASIC, and an RF telemetry coil and is capable of wirelessly transmitting digitized EMG data to an external telemeter mounted in a prosthetic socket. The prototype microsystem is powered by a near-field inductive link operating at 8 MHz with 10% DC power transfer efficiency. On-chip rectification and regulation produce stable 2 V and 2.7 V supplies with a DC current driving capability up to 100 muA. The EMG electrodes are interfaced with a differential capacitively-coupled amplifier with 38 dB closed-loop gain, 1 kHz bandwidth, and 78 nVradicHz input-referred noise floor. The amplified EMG signal is then digitized on chip using an 11-bit algorithmic ADC. The digital EMG data can be Manchester-coded and transmitted to the external telemeter using phase shift keying (PSK) modulation scheme on the same wireless link as the inductive powering system.

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