How to Use the IQ Fiber Master™ MT2780A to Diagnose PIM Problems on CPRI-Based Systems
■Passive intermodulation (PIM) is a growing problem within the wireless network industry. As more bands get turned up, the sub-6 GHz frequency spectrum gets increasingly crowded, more transmitters can mix with existing transmitters, and consequently more uplinks are vulnerable to intermodulation products that cause problems. The problem is also exacerbated by densification, whereby more antennas are being added to the network to improve coverage. This consequently introduces more RF power into the environment, further increasing the likelihood of RF mixing with non-linearities in the environment.
■Current solutions lack a method to simply diagnose a PIM problem quickly, particularly for a multi-band site. A multi-band site is defined as having multiple transmitters and receivers, making the RF environment complex and difficult to analyze. When an RF engineer encounters a PIM problem on a particular uplink, there is critical information that must be gathered before deciding on a PIM troubleshooting path:
▲Determining whether there actually is PIM versus just external RF interference
▲Analyzing whether the PIM is internal or external to the system
▲Measuring the amount of PIM (in dB) you have present in the system so you can get a quantified measurement of the severity
▲The level of de-sensitivity of your Rx paths as a result of PIM
▲The distance-to-PIM from the antenna to the PIM source
▲A list of transmitters in your system that contribute the most to PIM
■The IQ Fiber Master™ MT2780A PIM and RF analyzer is Anritsu’s newest CPRI-based solution that enables users to diagnose and monitor PIM problems on any LTE-based site, including ones that contain multiple bands within the same locations. It does its analysis by using the RF data from the CPRI link, which allows the analysis to be done while the site is live, using real-time cellular traffic.
■This application brief will introduce a method that utilizes the IQ Fiber Master MT2780A to gather the required information quickly, without disrupting service or disassembling the site. A simple table of possible troubleshooting methods are also discussed in the final section.
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Application note & Design Guide |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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2020-09 |
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Rev. A |
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11410-02831 |
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2.1 MB |
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