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Title: An analogue integrated circuit design for laser doppler blood flow measurement
Author: Gu, Quan
ISNI:       0000 0001 2450 8712
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2007
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Laser Doppler Blood Flowmetry (LDF) is a non-invasive optical technique for measuring microvascular blood flow in tissue. The existing LDF systems employ either scanning techniques or full-field imaging using discrete devices and digital signal processing units. However, the scanning systems have limitations in their imaging speed. The discrete full-field systems are not compact and at present are limited in bandwidth. This work deals with the design of a LDF system implemented with analogue integrated circuits. The design starts with the investigation of the design of each building block required in a single pixel and ends with a 4 x 4 pixel array. Four batches of chips were designed and fabricated with a standard O.35/Lm CMOS process. The first three chips were dedicated to the optimisation of the building blocks at the pixel level, and the fourth chip was dedicated to the 4 x 4 pixel array. In each pixel, the building blocks include a front-end, a bandpass filter and a frequency weighted filter. The optimisation of the front-end is based on the comparison between the simple front-end, feedback front-end and regulated cascode (RGC) front-end. The choice of the type of the bandpass filter and the frequency weighted filter is based on the comparison between the switched capacitor (SC), the operational transconductance capacitor (OTA-C) and the hysteretic differentiator (HD) circuits. With the analysis, simulation and measurement of the different techniques, the RGC front-end, OTA-C HD bandpass filter and OTA-C frequency weighted filter were used in the 4 x 4 pixel array as the result of the trade-offs between multiple design parameters. The 4 x 4 pixel array was used to measure the blood concentration and flow on the human finger. With the aid of the off-chip digital squaring and averaging, the change of blood concentration and flow before and after finger occlusion was clearly observed in both frequency and time domains. With the ultimate aim of scaling the 4 x 4 pixel array to a larger size, the system speed, price and size were estimated and compared with existing LDF systems. The analogue integrated circuit LDF system shows good trade-offs between speed, price and size and has the potential to cost-effectively fabricate a 64 x 64 array.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available