Low Power Wireless CMOS System-On-Chip X-Ray Dosimeter

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Yadegari, Behzad




Blood sterilization systems irradiate blood with Gamma or X-ray radiation to prevent transfusion-associated graft versus host diseases (TA-GvHD).

Present day irradiators use tags applied to the blood bags which change color when exposed to radiation of 25 to 50 Gy. This method is neither accurate nor efficient and results in considerable blood wastage.

This thesis investigates alternative solutions that are low power, easy to handle, compact and efficient. A floating-gate (FG) metal-oxide semiconductor field effect transistor (MOSFET) is studied for its application as a radiation sensor. FG MOSFETs have been employed for this application, but never using an RF-CMOS 0.13μm process suitable for RF-ID wireless readout. This work studies device optimization for best possible performance in radiation dosimetry. Devices are fabricated with different layer configurations to see how these affect sensitivity, linearity and power consumption. The final sensor measurements demonstrate a sensitivity of 6.5μA/Gy-1 with a maximum power consumption of 37μW.

This work also explores novel sub-threshold operation of FG MOSFET sensors for this application. This technique is shown to reduce the power consumption of such sensors, hence improving their figure of merit. Additionally, FG MOSFET devices are configured as an inverter, rather than a stand-alone transistor, to work as radiation sensors. This provides great reduction in the power requirements and is completely novel. These sensors are seen to consume channel current in the range of nA in comparison to μA consumed by the single MOSFET, while providing acceptable sensitivity values. Furthermore, the thesis explores photodiodes as X-ray power harvesting devices which could be provided with the sensor chip itself for a battery-less solution.

Finally, an e-fuse RF-CMOS based non-volatile (NVM) memory is realized for tag identification and control in a multi-sensor context. The memory has been tested under irradiated conditions to show its operation in the proposed environment. The results demonstrate the system-on-chip implementation of key components of an electronic blood irradiator system in a small form factor, with ultra-low power consumption. The proposed solution can improve dosimeter accuracy, allow automation of the process, and reduce blood wastage.


Engineering - Electronics and Electrical
Physics - Radiation




Carleton University

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Engineering, Electrical and Computer

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Theses and Dissertations

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