利用电热耦合效应的金属单点接触结构无源互调研究

A passive intermodulation (PIM) model based on electrothermal coupling effect is proposed to address the problem that current PIM model cannot explain the PIM mechanism and describe the experimental rules accurately. This model is further verified experimentally by using a metal point contact structure. First, a near-field coupling PIM measurement method based on waveguide slot is established, which makes the device under test (DUT) separate with the test equipment. This method overcomes the restriction in traditional PIM experimental research for measuring the whole microwave components, and realizes the research on the PIM effect of metal point contact structure. Then, the surface composition and the electrical contact characteristics of an aluminum metal point contact structure are investigated by EDX and I-V characteristics test, respectively. The results show that the oxidation and contamination existing on the metal surface dominates the PIM generation and degradation of metal contact. Moreover, the electrothermal coupling effect in microwave stimulating is proved to have significant impact on the contact impedance. Finally, a PIM model based on electrothermal coupling effect is proposed and verified by the experimental tests on metal point contact structures made of aluminum, brass and copper. Theoretical and experimental results show that, compared with the traditional empirical model or polynomial model, the proposed nonlinear contact model based on electrothermal coupling effect can improve the PIM calculation and prediction dramatically by giving a clear explanation of PIM's origin and mechanism.