We describe the design of a correlator system for ground and space-based VLBI. The correlator contains unique signal processing functions: flexible LO frequency switching for bandwidth synthesis; 1 ms dump intervals, multi-rate digital signal-processing techniques to allow correlation of signals at different sample rates; and a digital filter for very high resolution cross-power spectra. It also includes autocorrelation, tone extraction, pulsar gating, signal-statistics accumulation.
@article{arxiv.astro-ph/9908314,
title = {The S2 VLBI Correlator: A Correlator for Space VLBI and Geodetic Signal Processing},
author = {B. R. Carlson and P. E. Dewdney and T. A. Burgess and R. V. Casorso and W. T. Petrachenko and W. H. Cannon},
journal= {arXiv preprint arXiv:astro-ph/9908314},
year = {2009}
}