All around the world, mobile cell-sites suffer from inexplicable dropped calls and degrees of uplink degradation “deafness”. Many engineers know in their hearts that the cause is more than likely PIM (passive inter modulation). PIM just lies hidden in the cell’s RF infrastructure but until now there has been no way of diagnosing the level of the problem on site in order to set about curing it.
Summitek has finally brought to market two user friendly truly portable PIM “diagnostic measurement” tools iMT and iQA for use in the field. Both have the same high-power and effectiveness as their benchtop model which is the standard for laboratory PIM testing. It’s being demonstrated at CTIA (Central Hall C3, Booth 6221).
PIM often only shows up under full-power transit conditions. It is caused by a variety of factors such as arcing between surfaces that are not correctly prepared or where mating surfaces are not 100% clean or terminations not 100% torqued.
The route from transmitter to airwaves is a complex one – filters, diplexers, combiners, feeders, connectors, jumpers, and the antenna itself – and not only is every single component a candidate for causing PIM, but so also is the way it was installed one, three maybe five or ten years ago.
Says Wayne Skinner, VP Sales Interconnect technologies, “PIM is insidious, it slowly grows and the cell becomes more damaged, more ‘deaf’ - but no-one could investigate and explain why – until now.”
Conventional VSWR and ‘distance to fault’ testing are robust measurements in themselves, but incapable of finding PIM distortion and its causes; and even the low-power portable PIM testers are inadequate because they don’t have the power levels to simulate the system environments which cause the real-life PIM issues.
Summitek iMT and iQA field test units are both full 20w + 20w testers. Both are fully field ruggedized, capable of being dropped and stood upon (not that Summitek actively recommend such treatment) and can be easily taken by technician-in-van to any site and used to test and diagnose PIM issues, and once the suspect element has been replaced/repaired to test for a full “clean bill of health” on the entire RF system. There is even a small back-pack tester (iHA companion) which can be taken to the tower-top during identification and cure operations.
Engineers know that gaining an extra few dB of signal to noise ratio on the uplink receive path saves on lost calls and improves data thru-put. PIM cures effected with Summitek iMT and iQA portable field PIM testers have instances improving the noise floor by a massive 5dB delivering an environment which allows optimal receiver performance
Summitek forecasts a frightening rise in PIM issues as existing infrastructure is re-used for new technologies like 3G/UMTS and LTE.
Says Skinner “Feeders, filters and the like have been in-situ for years and they were built for either analogue or GSM single frequency operation. UMTS and LTE use wideband approaches so old empirical PIM solutions like using a different frequency are no longer an option. What’s more, because they are wideband instead of discrete transmission frequencies, the wideband carrier being transmitted creates a type of spreading effect of the third, fifth and seventh order intermods causing significantly raised noise floors for the uplink receivers.”
Although this is a potential minefield says Skinner, now with the Summitek iMT and iQA field testers it is possible to confirm end-to-end RF interconnection quality through the analysis of the presence of PIM - problems can be identified and rectified so that existing infrastructure can be re-used with the certainty of high quality operational use.
PIM-free RF components
From its leading position as the manufacturer of the laboratory standard Summitek PIM bench tester, the companies sister brands will also be on the CTIA booth (Central Hall C3, Booth 6221) showing:
Triasx HSPA proven Filters, Diplexers, triplexers, combiners and splitters
Triasx Sole supplier of RF products (Active solutions and Tower Mount Amplifiers) to the world’s fastest national mobile network
Allrizon radio receiver conditioning solutions, (filtering and amplification)
Allrizon Microwave broadband RF filter solutions from 2.4GH to 38GHz
Download here: http://fs.turtleconsulting.co.uk/PICS/IQA2000_001.jpg
Caption: Fully field ruggedized the Summitek iQA allows full on-site system testing and elimination of PIM – a major cause of cell site deafness.
Note to Editors:
For further information or to arrange an interview with Wayne Skinner please contact Turtle Consulting Group:
Phil Turtle firstname.lastname@example.org +44 7867 780 676
Or Debbie Ireland email@example.com +44 7727 016 633
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