Investigation of a microwave data telemetry link for a retinal prosthesis

In this paper, we investigate a novel approach of establishing a data telemetry link for a dual-unit retinal prosthesis at microwave frequencies (1.45 and 2.45 GHz) using a pair of microstrip patch antennas. Appropriately sized extraocular (25×25 mm) and intraocular (6×6 mm) antennas are designed to operate at both the frequencies using the finite-difference time-domain method, and the coupling between them is examined computationally in the presence of a 0.25-mm resolution human-head model. Good agreement between numerical and experimental coupling results is shown and it is observed that the eyeball acts as a dielectric lens for the implanted antenna, thus improving the coupling between the extraocular and intraocular antennas. Specific absorption rate (SAR) computations are also performed at both the frequencies, and the peak 1-g SAR value is calculated. Detailed analysis of the design issues of the antennas, results of the numerical and experimental coupling measurements, and SAR calculations are presented.