Phase Effects on Combined Passive Intermodulation From Multiple Sources

Signal distortion caused by passive intermodulation (PIM) poses a significant challenge to modern multicarrier communications and radar systems. This article is concerned with modeling the superposition of reverse PIM products generated by weak nonlinear sources and proposes means of PIM mitigation accordingly. The developed model is experimentally validated using an open-ended coaxial waveguide with a movable iron insert serving as the main PIM source. The study explores PIM interactions from multiple sources and introduces a new circuit comprising three negatively biased p-i-n diodes separated by 60° transmission lines. It substantially reduces reverse PIM by over 30 dB with a minimal footprint compared to previous studies. The potential of this circuit for measuring the reverse PIM phase is explored theoretically and experimentally for the first time, showing trends in agreement with a mean absolute error of 19.49°.