Improving communication with implantable systems has been an important topic of research due to various design constraints that include, but are not limited to, power dissipation, implant size, location of implant in the body, and regulatory standards. Up till now, RF has been the dominant part of such communication systems. Cross talk between the RF power link and the RF data link has been the major issue, therefore, a dual-band telemetry link is common in such applications to spectrally isolate data and power signal. These RF communication systems require a pair of coils having diameter several tens of millimeter and power consumption ranges from 1.5 nJ/bit to 3nJ/bit. The focus of this work is on optical wireless front end for retinal implant. Two different optical wireless...[ Read more ]

Improving communication with implantable systems has been an important topic of research due to various design constraints that include, but are not limited to, power dissipation, implant size, location of implant in the body, and regulatory standards. Up till now, RF has been the dominant part of such communication systems. Cross talk between the RF power link and the RF data link has been the major issue, therefore, a dual-band telemetry link is common in such applications to spectrally isolate data and power signal. These RF communication systems require a pair of coils having diameter several tens of millimeter and power consumption ranges from 1.5 nJ/bit to 3nJ/bit. The focus of this work is on optical wireless front end for retinal implant. Two different optical wireless front ends are presented. Both are designed in 0.18 um process. Both designs feature low power, robust ambient photocurrent rejection capability and occupy little area.

Circle Polarization Shift Keying has been utilized instead of conventional intensity modulation to isolate the signal from high background light. A novel integrating front end has been designed and simulated in 0.18um process to validate the concept. The receiver consumes 396 nW of power @ 32 Kb/s with a simulated FoM of 12 pJ/ bit.

Pulse Frequency Modulation has been utilized as an optical wireless receiver to recover the detected signal with high sensitivity. Due to the integrating behavior of the front end, the signal can be detected with relatively small input photocurrent which, effectively, reduces the area of the photodiode. Background photocurrent rejection capability has been achieved through a dynamic DC rejection scheme that consumes no static power at steady state except leakage power. The design has been simulated in 0.18 um CMOS process, post layout simulation results shows that it attains data rate of 100 Kb/s with a background photocurrent rejection capability of 42 dB. It dissipates 6 μW of power with a FoM of 60 pJ/ bit.