Practical Characterization of the Effect of the Transmission Carrier Phases in Passive Intermodulation

The effect of the phase of the input carriers has been traditionally neglected in the characterization of passive intermodulation (PIM) since standard two-tone PIM tests seem to be unaffected by phase variations of the excitation signals. However, the phase of the input carriers can be of relevance in many practical applications. This article is aimed at filling this gap in the technical literature. First, the existing theory explaining why the phases do not affect the measured PIM contribution for a two-carrier excitation but can be of relevance for generic multicarrier scenarios is summarized. PIM measurements for complex signals composed of several carriers with varying phases are then reported, enabling the practical characterization of this effect for the first time. Experimental results of the test campaigns are fully aligned with theoretical predictions, thus allowing us to identify those PIM contributions that can be affected by the carrier phases and assess the expected variation range in their amplitude level.