Ming's Qualifying Exam

Abstract:

Retinitis Pigmentosa (RP) and Age-Related Macular degeneration (AMD) are incurable retinal diseases that result in profound vision loss due to degeneration of the light sensing photoreceptor cells. However, the discovery that electrical stimulation of retinal neurons creates visual excitation in patients has inspired an electronic prosthetic device capable of bypassing the damaged photoreceptors.

In such a device, information relating to stimulation current (amplitude, pulse width, frequency), stimulation pattern is transmitted from external unit which includes a camera and image processing unit. A wireless telemetry link (also called data telemetry) is required for transmitting this information to the implant unit. Although the advances in semiconductor technology and circuit design have enabled high speed wireless communication and computing, these technologies are not directly transferable to biomedical applications due to the power consumption limits imposed on implantable devices. In addition to power limitations, interference from the power telemetry link casts special design requirements. In order to achieve high speed data recovery at low power consumption and circuit overhead, two data transmission schemes are proposed which employs DPSK (Differential Phase Shift Keying) and OOK (On-Off Keying) respectively. The modulation/demodulation blocks are defined based on system analysis including the interference from power telemetry signal. Matlab simulation, circuit simulation and initial experimental tests have been done serving as platform for future work.