Passive Intermodulation in Finite Lengths of Printed Microstrip Lines

TLDR

The paper focuses on the theoretical aspects of passive intermodulation generation in printed transmission lines. The study proposes a new model of transmission line length with distributed nonlinearity to elucidate PIM generation mechanisms. A model of transmission line length with distributed nonlinearity is proposed and validated by near‑field measurements of PIM product distributions along microstrip lines. Analysis shows that nonlinear mixing, power dissipation, and load matching drive PIM products, revealing fundamental properties of PIM generation in finite printed lines and identifying mitigation strategies, including that reverse PIM products arise from nonlinear scattering in matched lines.

Abstract

This paper addresses the theoretical aspects of passive intermodulation (PIM) generation in printed transmission lines. In order to elucidate the mechanisms of PIM generation, a new model of the transmission line length with distributed nonlinearity is proposed. The developed model has been validated by the near-field measurements of PIM product distributions along the microstrip lines. The contributions of nonlinear mixing, power dissipation, and load matching to PIM products have been analyzed in detail. The obtained results reveal the fundamental properties of PIM generation in finite lengths of printed lines with distributed nonlinearity and identify possible means for PIM mitigation. It was shown for the first time that the reverse PIM products in a matched transmission line with distributed nonlinearity are generated due to nonlinear scattering.