High-Spatial-Resolution Resonant Coaxial Probe for Near-Field Measurement of Passive Intermodulation

This article proposes a semi-rigid resonant-type coaxial probe for near-field passive intermodulation (PIM) source localization. Compared with existed resonant coaxial probe, the presented probe demonstrates enhanced capabilities in PIM source identification and higher spatial resolution, while simultaneously offering significant advantages including compact dimensions, simplified structural configuration, and cost-effectiveness. Experimental validation was conducted with conductive foam embedded inside a slotted coaxial transmission line as device under test (DUT). Besides, high-precision and efficient PIM source detection was achieved through a custom-built automated scanning system. Test results indicate that the proposed probe attains a spatial resolution of −1 mm at 740MHz for PIM characterization and subsurface PIM detection was also successfully demonstrated. The methodology presented herein holds practical significance for detecting and localizing PIM sources in microwave components featuring open or semi-open structural configurations.