Noise signal decorrelation in broad-band active phased array systems

The paper deals with the limitations of broad-band active phased array antennas used in radiometer systems for the reception of thermal noise from a far field source. It is shown that receive signal decorrelation causes loss of antenna gain and reduces signal-to-noise improvement when the beam is scanned in an electrically large phased array antenna with large relative bandwidth receive charnel. On the other hard, the excess noise produced by active receive modules does not combine through the combiner network due to decorrelation so that the active array noise floor remains as low as the single module noise level.