A fast 2-bit digitizer for radio astronomy

The design and performance details for a 2-bit digitizer operating at a 250-MHz clock rate are presented. The digitizer is part of a new correlator system for a three-element millimeter-wave interferometer. The performance of the digitizer circuit is analyzed in terms of threshold errors, indecision, sampling aperture width, and timing errors. For an input bandwidth of 125 MHz, digitizer distortion actually improves the sensitivity of the interferometer by about 0.3% but limits the dynamic range of the instrument to about 2*10/sup 3/.<
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