Retinal degeneration (RD) is the degradation of retina with progressive death of the retinal cells, which causes visual impairment such as tunnel vision, retinal detachment, loss of peripheral vision to total loss of vision. Trans-scleral electrical stimulation (TsES) therapy is proved to be a promising treatment for the retinal degenerative diseases, but the conventional wired therapy requires anesthesia at each treatment, which brings inconvenience and discomfort to the patients. A wireless solution is proposed that a miniaturized implantable medical device (IMD) is implanted underneath the skin and powered through wireless power transfer (WPT) methods.

In this thesis, a wirelessly powered TsES system for experiments on freely moving rodents is implemented. Near-field inducti...[ Read more ]

Retinal degeneration (RD) is the degradation of retina with progressive death of the retinal cells, which causes visual impairment such as tunnel vision, retinal detachment, loss of peripheral vision to total loss of vision. Trans-scleral electrical stimulation (TsES) therapy is proved to be a promising treatment for the retinal degenerative diseases, but the conventional wired therapy requires anesthesia at each treatment, which brings inconvenience and discomfort to the patients. A wireless solution is proposed that a miniaturized implantable medical device (IMD) is implanted underneath the skin and powered through wireless power transfer (WPT) methods.

In this thesis, a wirelessly powered TsES system for experiments on freely moving rodents is implemented. Near-field inductive coupling is used for power transfer, and the power carrier frequency of 40.68MHz is chosen in consideration of the device volume. The IMD is controlled by a MCU program remotely, and the communication between the MCU and the IMD is realized through ASK data link and LSK back telemetry. The IMD is fabricated in standard 0.18μm CMOS process, and the MCU program is optimized for reliable communication. Besides, special packaging structure is previously adopted to guarantee the functionality and robustness of the TsES system for experiments on freely moving rodents.

To enable more functions in the IMD, active rectification is used to enhance the power delivering capabilities. However, circuit delays including the comparator delay and gate drive propagation delay severely degrade the performance of active rectifiers. Current-injection based compensation scheme is commonly adopted to compensate for circuit delays, and is proved to be effective at frequency up to 13.56MHz. As the frequency goes up to 40.68MHz, current-injection based compensation becomes less competitive due to large power overhead and tricky control logic design. In this thesis, a delay compensation scheme is proposed to tackle the difficulties. The rectifier is fabricated in standard 0.18μm CMOS process, and its performance is verified with measurement results.