Relative phase measurement of passive intermodulation products

This paper studies relationship between phase shifts of carriers and passive intermodulation (PIM) products. Theoretical results have been obtained first through analytical derivation and Fourier transformation. And then a simple measurement method was proposed to conduct the relative phase shift test using easily available RF instruments. In this method, phase controllable RF signal sources were not required for test and only power levels are need to be measured. Microwave isolator with obvious nonlinear property was used as device under test. It's demonstrated that the relative phase shift of carriers lead to phase shift of PIM products. 3rd order PIM product behaviors as the theory predicts while 5th order PIM product shows different tendency with prediction to some degree.