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A new type of calibration standard is presented which produces a pair of microwave noise signals to aid in the characterization and calibration of correlating radiometers. The Correlated Noise Calibration Standard (CNCS) is able to generate pairs of broad bandwidth stochastic noise signals with a wide variety of statistical properties. The CNCS can be used with synthetic aperture interferometers to generate specific visibility functions. It can be used with fully polarimetric radiometers to generate specific third and fourth Stokes parameters of brightness temperature. It can be used with spectrometers to generate specific power spectra and autocorrelations. It is also possible to combine these features and, for example, to generate the pair of signals that would be measured by a fully polarimetric, spectrally resolving, synthetic aperture radiometer at a particular pair of polarizations and antenna baselines for a specified scene over a specified frequency band. Algorithms are presented to construct signals with the desired statistical properties. Also presented is a description of the key hardware design challenges that were associated with fabrication of the first unit. CNCS performance is demonstrated by characterization tests of a pair of microwave interferometer radiometer receivers.