The Generation Mechanism and Analysis 0f Passive Intermodulation in Metallic Contacts

The physical mechanism and analytical method of passive intermodulation in metallic contacts are studied. PIM interferences in metallic contacts mainly originate from contact nonlinearity. Several important nonlinear mechanisms such as electronics tunneling effects, multipactor discharge and contact mechanism are specially described. Power series analysis indicates that PIM power should vary as 3 dB/dB with the combined input power at equal amplitude two-carrier case. PIM power should vary log-linearly with the combined input power for carrier power ratio greater than 10 dB at unequal amplitude two-carrier and constant input power case; the strongest PIM for a given power is produced when the power at transmit carrier frequency closest to the IM frequency is about 3 dB higher than the other. Verification with related reference´s measured data shows that the used theory is right and practical