A high-speed digital correlator for radio astronomy

Design details for a high-speed digital cross correlator for the Owens Valley Millimeter Array are presented. The correlator uses ECL gate arrays operating at a 256-MHz clock rate to compute the real cross-correlation function for up to four independent frequency bands with bandwidths in the range of 2-128 MHz. For each baseline in the array the correlator provides 512 lags, giving a spectral resolution of 2 MHz at the maximum bandwidth. Two-bit digitization is used, and this results in a sensitivity of 0.88 relative to a perfect analog correlator. >