Influence of a foam supporter on passive intermodulation measurement using standing-wave coaxial tube method

The influences of dielectric loss due to supporting materials proximity to tested conductive materials is examined in terms of PIM characteristics. The examination is performed using the standing wave coaxial tube method, and foam with low dielectric constant is chosen as a supporting material. In this PIM-measurement method, the error due to the loss cannot be negligible especially in the calibration process to eliminate the frequency dependence of the measurement results. Therefore, a method to reduce the influence due to such loss is proposed in this paper. The proposed method employs a low-loss conductor such as silver wire, and its validity is confirmed. As a result, it is shown that the discrepancy in the calibrated process is reduced from 10dB to 1dB.