Correlation systems in radio astronomy and related fields

A comprehensive review of the theory and practice of analogue and digital correlation systems used in radio astronomy and its related fields is given. The correlators are discussed according to the following classifications: analogue, amplitude-limited, Stieltjes (or random reference), relay, modified relay, polarity coincidence, modified polarity coincidence, and multilevel correlators. The expected performance data and limitations of each type are discussed together with examples of use.