Data acquisition system using delta-sigma analog-to-digital signal converters

An improved oversampling, delta-sigma A/D converter for generating a digital output signal as a function of an analog input signal, said converter comprising:

• a delta-sigma modulator for providing an intermediate digital output signal as a function of said analog input signal, said modulator including means for reducing the electronic noise as an inverse function of the level of said analog input signal;
• and
• means for decimating the data rate of and for filtering said intermediate digital signal so as to generate a digital output signal.

A CT scanner comprising a source of X-rays, an array of detectors for detecting X-rays emitted by said source and received by said detectors, and a data acquisition system for processing signals generated by said detectors, said data acquisition system comprising a plurality of oversampling delta-sigma A/D converters, each of said delta-sigma A/D converters comprising:

• a delta-sigma modulator for providing an intermediate digital output signal as a function of said analog input signal, said modulator including means for reducing the electronic noise as an inverse function of the level of said analog input signal;
• and
• means for decimating the data rate of and for filtering said intermediate digital signal so as to generate a digital output signal.

A CT scanner comprising a source of X-rays, an array of detectors for detecting X-rays emitted by said source and received by said detectors, and a data acquisition system for processing signals generated by said detectors, said data acquisition system comprising a plurality of oversampling delta-sigma A/D converters, each of said delta-sigma A/D converters comprising:

• a delta-sigma modulator for providing an intermediate digital output signal as a function of said analog input signal;
• and
• filtering means for decimating the data rate of and for filtering said intermediate digital signal so as to generate a digital output signal at a view rate, fVR, said filtering means including a filter providing gentle roll-off within a frequency band of interest between DC and fINF, and roll-off at 2*fVR exceeding −100 dB/octave, wherein fVR is at least twice fINF.