A Multi-Channel Wireless Implantable Neural Recording System

Abstract

ABSTRACT YIN, MING. A Multi-Channel Wireless Implantable Neural Recording System. (Under the direction of Dr. Maysam Ghovanloo).

This dissertation presents a multi-channel implantable wireless neural recording (WINeR) system for electrophysiology and behavioral neuroscience research applications. This system consists of two units: a system-on-a-chip (SoC) transmitter unit and a receiver unit built with off-the-shelf components. A novelty of the WINeR system is in its utilization of a wireless single-slope ADC technique by inserting a wireless link in between a pulse width modulator and a time-to-digital converter (TDC). This technique not only offers the WINeR system the benefit of a single-slope ADC, but also makes the WINeR transmitter unit very simple, low power, and small in regards to chip area. In addition, by directly transmitting pulse width modulation (PWM) signal, the pulse rate over the wireless link is reduced to the sampling rate, while a moderate system resolution can still be achieved. Another novelty of this system is that its transmitter uses an asynchronous (clockless) topology and achieves very low noise levels by eliminating the on-chip clock. Some of the other features of this system are the wideband FSK demodulator and FPGA-based TDC in the receiver unit capable of achieving high resolution, low noise, low power, low cost, and ease of implementation.

A 32-channel WINeR transmitter prototype is implemented in a standard CMOS technology, and operates in the 900MHz ISM band. A prototype WINeR receiver is also built using off-the-shelf components with up to 75MHz bandwidth. A custom developed VC++ GUI running on a PC interface with the receiver unit through a USB port and facilitates data storage and visualization. In addition, detailed noise analysis is conducted both theoretically and experimentally to further characterize the performance of the system. Finally, the full functionality of the entire WINeR system has been validated from bench-top, and through in vivo experiments on rats.