The accurate measurement of microwave phase-shift using a dual-channel heterodyne system

A dual-channel heterodyne microwave phase-shift measurement system has been developed. This system is used to provide accurate transmission phase measurement of various devices and phase-shift standards from 50 MHz to 2 GHz. The system design and measurement uncertainties analysis are given in this paper. A beadless coaxial air line has been used as a phase-shift standard to verify the system performance and its phase-shift is calculated with consideration of its insertion loss. The measured phase-shift value agrees with the calculated values within the measurement uncertainties. The estimated phase measurement uncertainty is 0.055 to 0.2 degrees for variable attenuators with attenuation up to 140 dB.