Abstract: A microwave radiometer is formed of a set of frequency scanning antennas disposed parallel to each other and connected by a common microwave feeder. Signals of individual ones of the antennas are translated to different intermediate frequencies such that differences between the intermediate frequencies are proportional to baseline spacings between pairs of antennas of nested interferometers. A correlator containing parallel delay lines and a set of multiplier channels coupled to paired taps of the delay lines receives signals at the intermediate frequencies to produce a set of correlation signals. A two-dimensional Fourier transformation is applied to the correlation output signals to provide the power spectral density of microwave radiation incident upon the array of antennas.