A High Spatial Resolution Filtering Coaxial Probe for Near-Field Detection of Passive Intermodulation

In this work, a novel filtering coaxial probe is suggested for near-field passive intermodulation (PIM) test. Benefiting from the coupling structure of a half-wavelength coaxial transmission line resonator and its sharpened tip, the dynamic range and spatial resolution are enhanced. Perforated coaxial transmission line and conductive foam are used as device under test. High measurement efficiency is also achieved by a homemade automatic scanner system. Experiment results show that spatial resolution of the probe can be ~10 mm@720 MHz (~1/ $50~\lambda $ ) and its dynamic range is improved by ~10 dB compared with current non-filtering coaxial probe. The proposed method could be useful to detect and locate PIM of passive microwave components with open structure like planar circuits.