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S. K. Kelly, G. W. Swider, W. A. Drohan, J. L. Wyatt, J. F. Rizzo; Exploration of Optimal Coil Designs for Retinal Implant Power and Data Telemetry. Invest. Ophthalmol. Vis. Sci. 2007;48(13):674.
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© ARVO (1962-2015); The Authors (2016-present)
This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. Specifically, this presentation gives findings of an optimization process for our implant telemetry coils. The prototype implant receives power and image data via an inductive telemetry link. We explored a number of parameters relating to primary and secondary power and data coils.
Parameters of the coils themselves were explored, including resistance, inductance, quality factor, and self-resonance frequency. In addition, we examined the interaction between the sets of coils, and between the coils and other system components, such as the rectifier system. Coil interactions were modeled from first principles, both analytically and numerically. Numerical calculations and plots were done in Matlab, which was also used in some cases to search for optimal designs. Coil resistance and inductance calculations were done analytically by hand, the latter with the help of numerical tables from an inductance calculations book. Broader system efficiency calculations were done from first principles. Coil impedances were tested on a 30 MHz precision LCR impedance analyzer. Coil and system performance was also tested on the lab bench using power and data transmitters.
Our data coil was found to have a self-resonance below its 13.56MHz data carrier frequency. Our calculations showed that reducing the number of turns in the coil (thereby raising its self-resonance frequency) would raise the voltage at our data receivers. Also, our power system quality factor was raised through fewer turns of thicker wire and more careful resonance in our 125kHz power telemetry channel. Additionally, our primary coils have been optimized to deliver maximum integrated field to the distant secondary coils, while minimizing sensitivity to eye movement. Testing continues as we revise and improve our system and explore larger system efficiency questions.
Our power and data telemetry coils and systems have been redesigned based on these explorations to give more reliable and efficient data transmission and reception, and more efficient and stable power supply generation. More work is being done to improve these calculations and expand the work to improve our whole system.
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