Accurate measurement of microwave phase-shift from 2 to 18 GHz using heterodyne receiver

A dual channel phase-shift measurement system from 2 to 18 GHz using heterodyne receivers is described. The calculated phase-shift of a beadless air line has been used to verify this measurement system. The differential phase-shift measurement uncertainty is estimated to be 0.08°-0.31° for a two-port device with variable attenuation from 0 to 140 dB. The phase-shift measurement results of a 0-140 dB step attenuator at 18 GHz are presented.