Passive intermodulation (PIM) is the mathematical mixing of two or more desired signals to generate a family of undesired signals. PIM is generated when high power signals encounter a non-linearity which can be in the RF path or nearby the antenna(s). For a refresher on “What is PIM?,” see my CommScope Definitions blog post.

At a cell site, PIM can be caused by downlink (Tx) frequencies mixing, and if any of the new undesired signals fall on an uplink (Rx) frequency, network degradation can occur. As an example, using the typical antenna PIM specification of -150 dBc with two 20 watt (43 dBm) carriers, the 3rd order PIM level would be -107 dBm. That level would become a strong interferer for a receiver with a Reference Signal Received Power rating of -120 dBm.

PIM-screen-calculatorCLICK TO TWEET:  New Universal PIM Calculator from CommScope Supports FDD, TDD

Since over 50 different LTE frequency bands have been defined by the 3GPP standard, there is a real possibility that many combinations could have the potential for PIM. To evaluate the specific combinations a given operator may encounter, CommScope has introduced a new Universal Band and Block PIM Calculator. The calculator includes regional tabs that contain the default bands used in that region and supports both frequency division duplex (FDD) and time division duplex (TDD) frequency bands.

For FDD bands, clicking a Tx block automatically activates the companion Rx block; however, any Rx block can be turned on or off independently. For TDD bands, the first click activates both Tx and Rx, while a second click activates Rx only. An option to synchronize all TDD blocks is also available. Unlike our older PIM calculators that used a stepped single frequency approach, the new calculator is able to analyze wideband signals used in 3G and 4G networks.

Once an operator selects the blocks in the bands they are using, the calculator can determine if any 2nd, 3rd, 4th or 5th order PIM combinations (hits) exist. A window shows the number of discrete hits found and there is a button to view the hits file. Finally, a percentage of involvement number is shown below the involved blocks.

If for any reason the default bands and blocks do not fit an operator’s requirements or if new bands are added in a region, the calculator can be easily re-configured by your local CommScope representative. It is totally re-configurable all the way down to changing the start and stop frequencies of desired bands and blocks. It can even be re-configured with an operator-specific tab which includes only the specific bands that operator is using.

The Universal Band and Block PIM Calculator is available on the CommScope web site at http://www.commscope.com/resources/calculators. You will also find other PIM and RF Path calculators there. Feel free to explore them all and let me know if you have any questions.

About the Author

Lou Meyer

Louis Meyer, P.E., is director of technical sales for CommScope Mobility Solutions. Lou has spent a lifetime advancing RF technology, taking it from the drawing board to practical use. Over the years in various roles with Allen Telecom, Andrew Ltd. and CommScope, Lou was responsible for supporting the sales teams for such solutions as remote antenna control systems, transmission lines, diplexers and other important components. Prior to joining Allen Telecom, Lou worked with Decibel Products as vice president of antenna design and vice president of international OEM relations. Earlier, Lou worked with Harris Corporation in RF communications and Bendix Corporation in their missile systems division. Lou holds five patents and has been active as a chair and vice-chair of the TIA’s TR-8.11 Antenna Standards subcommittee. He earned his bachelor of science degree in electrical engineering from Marquette University in Milwaukee, Wisconsin and is currently a registered professional engineer in the state of Texas.

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Comments

2 comments for "New Universal PIM Calculator Supports FDD, TDD"
Hilmy Muhammad Tuesday, December 05, 2017 1:16 AM

Thanks for the good tools.

I'm working for Power Link Trnasmission ( M ) Sdn Bhd which is one of Commscope product Distributor in Malaysia.

Would be great if you can defined the PIm calculator specific for Malaysia.

Any Commscope representative that can be contacted ?

Lou Meyer Tuesday, December 05, 2017 10:47 AM

The internet shows that Malaysia uses 3GPP Band 1, Band 3, Band 7 and Band 8. If you agree that these are correct, I will generate a Malaysia specific tab to the PIM Calculator and send it to you. If each carrier is assigned specific blocks in each band throughout the country, this can be incorporated also.

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