Integrated CMOS Optical Sensing Architectures for Frequency-Domain Near-Infrared Spectroscopy.
Abstract: This work
presents the integrated CMOS optical sensor for frequency-domain near-infrared
spectroscopy (NIRS), which is rapidly advancing as a cost-effective and efficacious tool
for functional studies and imaging of breast tissue, brain tissue, and skeletal muscle.
The frequency-domain NIRS (FD-NIRS) is capable of readily measuring tissue optical
properties by combining the results ... read moreusing light at several NIR wavelength (650 nm ~ 950
nm) . The measured tissue optical properties then can be used to generate the image of
the tissue for cancer detection. CMOS optical sensor is able to monolithically integrate
the photodetector, amplifier and signal conditioning circuitry on the same chip, thus
enabling an truly miniaturized noninvasive instrument which is portable, unobtrusive,
low-cost, low-power, and robust to motion artifacts. Moreover, each of the building
blocks can be optimized to achieve better system performance to fully exploit the
benefits of FD-NIRS techniques. Ultimately the CMOS integration would enable the
realization of systems for concurrent measurement of multiple diagnostic modalities,
thus improving diagnosis validity. System architectures and key building blocks towards
the monolithically CMOS integrated phase sensitive optical sensor are extensively
investigated in this work. Photodetectors implemented in standard CMOS process are firs
studied. CMOS avalanche photodiode, delivering superior responsivity with high
bandwidth, is preferred for FD-NIRS system. Detailed derivation reveals that the
conventional wideband TIA input noise can be minimized by reducing the TIA bandwidth.
Both the zero-crossing phase detector and the mixer phase detector are analyzed in terms
of phase noise and phase error. Two integrated optical sensors are implemented in 180 nm
CMOS technology for FD-NIRS system. The first one is a monolithically integrated optical
sensor using on-chip n-well/p-sub photodiode with zero-crossing phase detector.
Experimental results confirmed that the optical sensor exhibits very good linearity for
both phase and amplitude measurement. The second one uses a novel frequency-mixing TIA
(FM-TIA) to dramatically reduce the front-end noise by implementing a narrowband
response. The proposed FM-TIA incorporates a T-feedback resistor network with time
varying resistor to simultaneously demodulate and amplify the photodiode current, which
can reduce both the design complexity and power consumption. The measurement result
reveals more than 15 times noise reduction with good
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Electrical Engineering.
Advisor: Valencia Joyner.
Committee: Sergio Fantini, Tom Vandervelde, and Joel Dawson.
Keyword: Electrical engineering.read less