Practical Determination of Passive Intermodulation From Modulated Signals in Satellite Applications

Passive intermodulation (PIM) measurements are typically conducted with a simplified test scenario composed of two radio frequency (RF) carrier tones operating in continuous wave (CW). However, satellite payloads tend to operate with a more complex scheme, where modulated signals are present at each transmission channel. This article aims at linking both PIM scenarios. A novel procedure is developed to obtain, from measured data obtained using two CW input tones, the spectral distribution and amplitude of a PIM contribution originated after exciting a nonlinear device with modulated signals. The technique determines the spectral distribution of the PIM term of interest from the spectrum of the input signals, and evaluates its amplitude from a recently formulated PIM power conservation rule. Moreover, an extensive PIM test campaign providing novel and valuable experimental data for the topic of PIM under modulated signal excitation has been carried out. The results obtained for a wide range of test scenarios exhibit a good agreement with theoretical predictions, thus providing a practical validation of the proposed technique.