Hidden PIM source discovered in mobile data connections

Research by Hughes Electronics and London Southbank University has found that humidity makes a significant contribution to passive intermodulation (PIM) in cellular networks. PIM is a series of resulting signal harmonics and distortions that emerge between two or more interacting signals when transmitted through passive components such as cables and connectors, causing unwanted interference and degradation of wireless communications.

The group found that humidity deposits a layer of salts and other airborne contaminants which interfere with ‘clean’ signal transit. Though almost impossible to see, the salts, deposited during the evaporation process, are electrically conductive and play havoc with skin effect signal transmission. They instigate surrogate (signal) pathways, causing parallel path and harmonic signals and distortions, which are a root cause of PIM.

To counter the effect, Hughes has designed an intelligent IP68-rated cap for connectors with a humidity indicator. The cap, which protects open connector interfaces from mechanical damage, dust and humidity is transparent, and incorporates a blue indicator that visibly turns to pink when it detects the presence of humidity. It is possible to determine the amount of humidity present by the shade of colour; instructional information is provided with each cap to help the user.

Approved by most major UK networks, the device is economical to deploy and can save companies many wasted man-hours of PIM diagnosis and trial-and-error remedies tracking down sources of PIM they simply cannot see. The screw-on caps are rugged yet lightweight and require no special tools, making them economical to deploy. They are available for industry-standard 7/16 and 4.3/10 connectors.