A pixel-level A/D converter for the imaging array of an advanced interferometer

Abstract

The objective of this thesis is to investigate the feasibility of pixel-level analog-to-digital conversion as a solution for the imaging array of the advanced interferometer project at Lincoln Laboratory. Six different pixel-level analog-to-digital conversion methods are examined. Four of the conversion methods are discarded after preliminary analysis because accuracy requirements cannot be met given the high-speed and area constraints. Two of these conversion techniques (voltage-to-frequency and sigma-delta). are further analyzed because they show promise to fit in a 60 [mu]m x 60 [mu]m area and be able to perform 14-bit, analog-to-digital conversion at frame rates of 5000 Hz. As a result of the analysis, the voltage-to-frequency converter is also discarded because comparator inconsistencies degrade the accuracy below specifications. The sigma-delta converter individually meets the imaging array requirements, but high power supply dissipation, large parasitic capacitance and noise introduce by other converters make pixel-level sigma-delta conversion impractical with current technology.