RF Powering For Embedded Glaucoma Sensors in Miniature Packages

This paper will focus specifically on the ability to use radio frequency (RF) radiation to remotely power a wireless device implanted within an eye. We use this technique to charge a glaucoma monitoring system which has been implanted, tested, and analyzed within a porcine eye. Implantation within the eye poses stringent restrictions on size which constrains the design of both the circuitry and antenna. The presented work shows the feasibility of coupling sufficient power through biological tissue to an implanted system. Embedded antennas for receiving the RF power have been implemented in both low-temperature co-fired ceramics (LTCC) and polymer substrates (Duroid RT5880). The received power was used to charge the internal power storage unit on the glaucoma monitoring device. RF powering is feasible for this application because the system will be inserted right beneath the surface of the eye where the attenuation through the thin layer of ocular tissue is only about 5 dB [1]. This work tests two antenna structures, an onboard inverted-F antenna which couples sufficient power to charge the implant within 20 seconds, and a smaller LTCC embedded antenna which requires a charge pump due to lower receive powers. 1