Examination Committee

Prof Philip K T MOK, ECE/HKUST (Chairperson)
Prof Wing Hung KI, ECE/HKUST (Thesis Supervisor)
Prof Chi Ying TSUI, ECE/HKUST (Thesis Co-supervisor)
Prof Howard LUONG, ECE/HKUST
 

Abstract

Retinal degeneration (RD) is the degradation of retina with progressive death of the retinal cells, which causes visual impairment such as tunnel vision and blindness. Trans-scleral electrical stimulation (TsES) therapy is proved to be a promising treatment for the retinal degenerative diseases, but 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, and the power carrier frequency of 40.68MHz is chosen to achieve a small 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 a standard 0.18µm CMOS process, and the MCU program is optimized for reliable communication. Besides, special packaging structure is 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 logics design. In this thesis, a delay-based compensation scheme is proposed to tackle the difficulties. The rectifier is fabricated in a standard 0.18µm CMOS process, and its performance is verified with measurement results.