Effects of broadband noise in radio-frequency six-port scattering-parameter measurements

Significant errors can arise in six-port metrology if broadband noise is present on the source signal. In order to describe noise effects, six-port analysis has been extended to include junction parameters which allow for noise correlations. The effects are demonstrated by means of a theoretical example and by reference to white-noise excitation of a six-port reflectometer operating at 10 MHz¿1 GHz. Errors of the order of 0.2% in a reflectivity of 1.0 may result if an unfiltered broadband source such as a synthesiser is used.