Practical Fixture Design for Passive Intermodulation Tests for Flexible Metallic Contacts

Passive intermodulation (PIM) commonly exists in non-ideal metallic contacts. Since PIM typically represents an extremely low level of nonlinearity, it has not drawn enough attention over the years except for extremely high-power applications such as base stations. However, in recent years, the study on PIM has become essential in universally used consumer electronics design because of the higher requirement on the radio frequency (RF) sensitivity of wireless communications. The metal contacts caused PIM can create the sideband spectrum to interfere with the receiving band in the frequency divide duplex (FDD) mode. Therefore, the study on PIM for the frequently used flexible metallic components is important in the industry. The PIM characterizations for the flexible components at least demand the compression variability and the capability to inject high-power signals while monitoring the sideband spectrum. It is preferred to have the access to measuring more relevant quantities. This paper aims to summarize the practical experience in designing a high-dynamic range and multi-purpose applicable test setup for characterizing PIM in the flexible components. Capabilities to precisely measure/control PIM, gap variability, tilted angle variability, and DC resistance (DCR) are presented with measurement examples.