Design of Electrically Small Intraocular Antenna for Retinal Prosthesis System and Its Validation

Objective: This paper presents an ultra-miniaturized circular-shaped triple band microstrip antenna as an intraocular unit applicable for retinal prosthesis. Methods: The reported antenna is developed by modifying a conventional circular-shaped patch with a pair of open-ended circular annular rings and a semicircular ring-loaded rectangular stub. Additionally, a shorting pin is used at the periphery of the patch to achieve the frequency bands of interest. Further, to make the structure electrically small and accommodate highly dense electrodes, the circular ground plane is modified by making symmetrical slots over the four quadrants and edges. Specific absorption rate distribution for 1g and 10g of different tissue layers over three operating frequencies has been studied by placing electromagnetic sources at different locations. Results: With these arrangements, the proposed strip antenna offers multiband operation within the frequency band of 1.25 GHz (1.13-1.46 GHz), 2.45 GHz (2.24-2.66 GHz), and 3.32 GHz (3.09-3.50 GHz). Besides, circularly polarized radiation has also been achieved at 1.25 GHz with a 3-dB axial ratio bandwidth of 10 MHz. Conclusion: Finally, the proposed antenna structure is fabricated, and its measured performance metrics are in close aggreement with the simulated parameters. Significance: The proposed antenna's performance inside a customized canonical eye model (DMCM) and anthropomorphic Zubal head model is studied and compared with the prior studies.