Design of Miniaturized Antenna and Power Harvester Circuit on the Enucleated Porcine Eyes

This letter describes a prototype of a miniaturized rectifying antenna (rectenna) design for the wireless powering of an ocular device. In contrast to the conventional on-lens loop antenna, this letter presents a loop antenna with stepped structures for optimal impedance to the rectifier. The return loss of the antenna less than -15 dB at 3 GHz is accomplished in a contact lens with a diameter ranging from 10 to 15 mm. Additionally, the radio frequency (RF) rectifier and voltage-boosting network (VBN) are optimized to enhance the power conversion efficiency (PCE) by using the voltage boosting technique. Experimental results indicate that the optimal rectifier, which is fabricated with the TSMC 0.18- μm process, produces a dc output voltage of 2.94 V and a conversion efficiency of 31% across a resistive 3.5 k Ω load with an input power of +9 dBm. Moreover, the rectenna under the experiment with an enucleated porcine eye can be powered wirelessly with a transmitting device at a distance of 4 cm. The output power is 2.01 mW with a transmitting power of +32 dBm for the wireless ocular physiological monitoring (WOPM) system. Importantly, this letter demonstrates the feasibility of an optimal miniaturized on-lens rectenna design, capable of overcoming the RF power attenuation on the ocular tissue to increase the delivering distance and reduce the transmitting power.