UBC Theses and Dissertations
Biomedical telemonitoring systems with an emphasis on in-stent restenosis monitoring Keikhosravy, Kamyar
Advances in microelectronic technologies have facilitated implementation of leading-edge circuits particularly in the realm of ultra-low-power circuits and systems. The focus of this thesis is on the design of reliable integrated solutions for telemonitoring of biomedical implants. In particular, we focus on diagnosing in-stent restenosis (re-narrowing) of coronary arteries after angioplasty. To achieve more efficient wireless power delivery, a modified version of conventional medical stent, namely antenna stent or stentenna, is used. In this work, two different systems are designed and fabricated in a 0.13-μm complimentary metal-oxide semiconductor (CMOS) process. The first telemonitoring system converts the capacitive changes of the (pressure) sensors directly to a corresponding frequency change which will be transmitted to the external reader. Unique to this design is the alignment unit which is designed to improve the physical alignment of external inductive antenna with the implanted stentenna for the purpose of wireless power transfer. The system starts operating with the rectified voltage of as low as 500 mV while consuming 4.15 μW, 3.4 μW of which is consumed by the transmitter. The system is designed such that, in alignment mode, the frequency of the pilot signal is directly proportional to the value of the rectified supply voltage. The monitoring unit, start operating from the supply voltage of 870 mV while drawing 111.25 μA. This system has been successfully tested in an in-vitro setup. The measured sensitivity of the system is 555 kHz/fF. This system is capable of detecting capacitance change of as low as 1.3 fF. The sensor interface circuit of the second system consists of a capacitance-to-voltage converter and the transmitter includes a voltage-to-frequency converter. The frequency for the transmitted signal is proportional to the changes of the capacitance of the sensor. Measurement results of a proof-of concept prototype show that the system operates from a harvested supply of as low as 350 mV (from input power of -43.76 dBm at 1.25 GHz) while drawing less than 100 nA from its harvested supply. The sensitivity of the system is measured to be 55 kHz/fF.
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