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2006
Conference Paper
Titel
Design and evaluation of a CMOS-photosensor with in-pixel sigma-delta modulator for x-ray computed tomography
Abstract
A multi-channel sigma-delta-type analog-to-digital converter has been designed for data readout in CT scanners. A test-structure with a 4 x 4 photodetector array has been fabricated in a 0.8 µm CMOS process. Aiming at an integrated solution towards a "digital pixel", each sensor element is formed by a photodiode and a third-order sigma-delta-modulator. The switched-capacitor circuitry has been realized as a fully differential-path design. Test measurements have been carried out and analyzed in terms of dynamic range and noise. Simulations on layout level have been performed. A digital post-processing scheme has been devised for decimation and low-pass filtering of the modulator outputs.