| Chronic recording from individual axons and fibers in the peripheral nervous system (PNS) is a long pursued goal to further our understanding of the nervous system and for potential control of prosthetic devices and stimulation of paralyzed muscles. This thesis demonstrates the development of a new, totally implantable system to record neural signals from axons and fibers in the PNS using the nerve regeneration of the PNS. The system is composed of a nerve regeneration electrode (sieve electrode), a radio-frequency (RF) telemetry link, and on-chip signal processing and RF interface circuitry.;The electrode structure contains a large number of small holes through which axons of a severed nerve will regenerate and reinnervate its target organs. The small holes are surrounded by 100-200 ;An inductively-coupled RF telemetry link has been developed using two small circular coils to transmit power and bi-directional data to a small chronic system, eliminating the need for cables and wires. The link is driven by a high efficiency class E amplifier, which is amplitude-modulated for transmitting control data to implanted on-chip circuitry.;The on-chip circuitry for a small implantable neural recording unit has been developed to interface with the RF telemetry link and for signal processing. The on-chip circuitry generates a 5 V supply, the clock signal, and control data from the RF signal, and allows simultaneous recording from any user-selectable 2-of-32 channels. These signals are amplified, multiplexed, and digitized with an on-chip low-power (2mW) current-mode analog-to-digital converter before transmission to outside world using passive telemetry. The full functionality of the on-chip CMOS circuitry has been verified by fabricating it at the University of Michigan. The on-chip circuitry contains more than 5000 transistors, dissipates about 90 mW of power, and results in an implantable unit which measures 5mm x 8mm x 2mm. This is the first chip of its kind that combines signal amplification and filtering, low-power analog-to-digital conversion, and bi-directional RF telemetry for power and data transfer all integrated monolithically on a single chip. |
