Two engineers review lessons learned from a webinar, using Post-It notes on a glass wall.

5 Key Takeaways from the 3M PIM Mitigation Webinar

Did you miss the “Novel PIM Mitigation Techniques for Wireless Network Infrastructure” webinar? Watch it now – or review a few highlights below:

1) Existing PIM mitigation solutions are not intended to address conducted PIM
Radiated Passive Intermodulation (PIM) is generated by a non-linear device directly irradiated by the antenna. In these cases, no induced currents are involved; the antenna itself emits signals that excite nearby non-linear objects, which then radiate PIM back to the antenna. – and so most popular PIM mitigation solutions focus on addressing this kind of PIM. But because conducted PIM is the result of currents in the structure rather than signals from the antenna, traditional solutions like metal shielding are not effective.

2) Conducted PIM can be significantly reduced by using magnetic absorbers
Traditional radiated PIM shielding techniques – like metal foils – have little effect at mitigating conducted PIM. The signal just propagates over the shielding material and continues into other parts of the structure. But a composite of magnetic particles in a polymer resin has demonstrated the ability to reduce and mitigate PIM in both lab and field experiments.

3)Measuring conducted PIM is practical
Because PIM can be highly time-variant over short and long periods – depending on the frequency band, corrosion and other wear and tear on the structure, demands on the network, etc., a common challenge is creating reproducible data. By testing in a controlled environment using an anechoic chamber, a variety of antennas, PIM analyzers and other test equipment, 3M has been able to demonstrate repeatable performance with a high level of statistical confidence. Field tests with live sites were then used to validate the results, including cumulative PIM reduction of all RX branches and 700MHz bands for each site, even with only one sector treated and no other PIM mitigation or hygiene.

Chart showing cumulative PIM reduction across a range of test sites.

4)Absorbers are not created equal
The optimal PIM solution requires the right combination of material and thickness, placed in the right locations – correct installation is important to effective performance. Take a look at this comparison of absorber material placements from 3M testing:

Chart showing PIM Reduction based on absorber placement, across a range of materials and locations.

5)Quick and simple solutions are available
Simulation, lab testing and field trials have has determined an effective combination of material and placement – and it turns out that it can be applied in just a couple of minutes with minimal training. Check out the 3M™ PIM Reduction Kit 1300 for more.