If you have experienced deploying W-CDMA and LTE networks, PIM issues may probably have concerned you for quite some time. Now if you are deploying 5G, especially C-band (3.1 GHz ~ 3.98 GHz) with TDD systems, are you out of worries for PIM?

Traditional TDD-based systems do not usually suffer from passive intermodulation. C-band is different, though. The reason? C-band systems are commonly being deployed at existing cell sites with various LTE FDD bands that might cause PIM.

Old Issue, New Problems?

PIM has been a thorn in the side of installers and mobile operators since the first wireless network went live. As a refresher, PIM is created when two or more frequencies are mixed in a non-linear fashion in a passive circuit. Please refer to our technical pages for a refresher of PIM.

Network performance is lowered, as PIM interferes with uplink receive frequencies of an LTE or 5G network and generates significant intermodulation signals. Improved network capacity and coverage are achieved when PIM is not a major factor in signal transmission, so networks KPIs are met.

The rollout of 5G adds multiple frequency bands and carriers within those bands to the overall RF spectrum. A higher risk for crossband PIM is created, as a result. The potential for PIM is greater due to co-locations and the integration of multiband combiners for higher power applications – common in macro systems. Higher-order modulation techniques, smaller channel spacing, and multiple transmissions using a single 5G antenna also increase the possibility of PIM.

Higher frequencies and bandwidth are necessary for high-band and wideband LTE and 5G networks. The high-powered signals generated by these base stations can cause added interference issues, including PIM.