In this dissertation design of a fully integrated frequency-domain Near Infrared Spectroscopy (fd-NIRS) system is discussed. The fd-NIRS system measures optical properties of the tissue under test to detect if there is any anomaly. Two chips are introduced for fd-NIRS application. The proposed systems measure phase and amplitude of the modulated optical signal with high precision and compare with the detected light to accurately calculate the optical properties of the tissue under test. The first chip, implemented in a 180nm CMOS process, is measured to characterize the phase and amplitude detection accuracy. The second chip is designed and implemented using a 65nm CMOS process. The proposed heterodyned fd-NIRS system includes a high-resolution wide-band phase-locked loop that provides modulating frequenciesfrom 50 MHz to 1GHz. A logarithmic analog amplitude detector provides accurate measurements of the modulated signal attenuation. The heterodyne receiver architecture includes a novel phase detector designed based on a three-stage limiting sense amplifier that allows for precise measurement of the phase with 1◦ phase resolution. The integrated circuit is designed to work with an external laser diode and avalanche photodiode (APD) to implement the complete fd-NIRS sensing system. The digital phase detector interface is designed to facilitate the optical measurements. The overall measurement result shows a promising path toward scalable and wearable optical sensing systems based on frequency-domain near-infrared spectroscopy.

Spin transfer torque (STT-RAM) is a fast, scalable and non-volatile memory technology. These characteristics make STT-RAM one of the best candidates among memories that can be used for space applications. However, understanding of radiation effects on memory cells and the related circuitry is necessary to avoid failure in a high radiation environment. Energetic gamma and neutron particles may strike on sensitive circuit nodes and induce a current by electron/hole pair generation. Radiation induced current potentially leads to read/write failures. In this work, we analyzed the effect of radiation on the STT-RAM sense circuit and proposed a radiation hardened circuit. The sense circuit is implemented in 45 nm CMOS technology. Simulation results show that the proposed circuit is immune to radiation pulses up to 400 Krad.