The Harvard Minicorrelator

A 1-b digital cross correlator for use in radio astronomy was designed and built at Harvard. Although only 16 channels (lags) were built in hardware, a recycling scheme allows the incoming data to be processed through the correlator several times over to multiply the number of hardware channels by a factor that can be quite large at low sample rates. For example, for a spectral window of 400 kHz, 112 lags can be computed and for 125 kHz, 400 lags. To do this the correlator is connected to a minicomputer (Supernova) for both input and output and so it is treated as a peripheral processor. The same computer performs the Fourier transforms and displays the spectra.