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• In a linear system there will be two output frequency signals in the case of two input frequency
signals.
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• In a non-linear system new frequency signals are generated in the case of one input frequency
signal, we will have Harmonics.
• In a non-linear system new frequency signals are generated in the case of two input frequency
signals.
• The new frequency signals are known as intermodulation products and this phenomenon is called
intermodulation.
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DC
Fundamental
Second
Harmonic
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Third
Harmonic
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• The central frequency of the intermodulation product is expressed by the following formula: fM = mf1± nf2
• The order of intermodulation products is the order m+n
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• Multi-carrier co-transmt;
• The antenna system has nonlinear passive components.
• The intermodulation product falls into the receiving band
of the carrier.
• The level of the intermodulation product falling into the
receiving band of the carrier is large enough.
‫عغففتنتتت‬
1. Channel PIM
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Contaminated surfaces or contacts due to dirt, dust, moisture, or
oxidation.
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Mechanical joints are loose due to insufficient torque, poor
alignment, or inadequate contact surface preparation.
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The mechanical joint is loose and causes shock or vibration
during transportation.
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The metal or shavings inside the RF connection.
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In the preparation process, the hollow inner conductor with oval
shape is over-enlarged or made.
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Different metals in direct contact.
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Immediate metallic objects in the direct beam and side lobes of
the transmitting antenna, including rusted bolts, roof flashes,
vent pipes, pull wires, etc
2. Spatial PIM
• The AAU and passive antennas are installed too close.
• The main lobes of AAUs and antennas overlap, which
affect each other.
• To prevent the PIM from being radiated from space, the installation
suggestions are as follows:
Horizontal installation distance (edge-to-edge) > 500 mm
Vertical installation, the value is greater than 500 mm.
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• In below case, PIM interference is generated because the
antenna side lobe radiates to the rear of the AAU.
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Assume that PIM interference signals generated during downlink scheduling fall within the uplink
frequency-domain range of a cell.
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Therefore, it affects the uplink network performance of the cell.
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Hardware Check Method
PIM Master
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To mitigate the impact of PIM interference on the network, Huawei provides the intelligent PIM
interference avoidance solution.
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During uplink scheduling in a victim cell the non-interfered RBs are preferentially selected for
scheduling based on detected frequency-domain positions of interfered RBs.
This reduced the frequency- domain range of PIM interference.
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This function calculates the frequency- domain positions of RBs that cannot be used for downlink
scheduling of interfering cells and avoids these RBs as much as possible during downlink scheduling
to reduce the frequency–domain range where PIM interference occurs.
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The downlink power reduction function takes effect in the interfering cells to reduce the strength of
PIM interference. This function directly reduces the downlink transmit power of interfering cells.
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It is recommended that channel isolation for PIM interference avoidance be enabled when uplink
KPIs significantly deteriorate and the uplink becomes basically unavailable due to strong uplink PIM
interference.
In this case the transmit channels specific to different carriers can be isolated to mitigate PIM
interference.
• For 4T4R cells the number of downlink channels of two carriers sharing the same channels is
reduced from 4 to 2
• For 8T8R cells the number of downlink channels of the two carriers sharing the same channels is
reduced from 8 to 4.
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Before Frequency and Bandwidth change
3rd Order Product
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Note: As frequency range in this tool can be select just by specific blocks
it may not have accurate results, it calculate whole block frequency ranges.
Before Frequency and Bandwidth change
5th Order Product
Note: As frequency range in this tool can be select just by specific blocks
it may not have accurate results, it calculate whole block frequency ranges.
‫عغففتنتتت‬
After Frequency and
Bandwidth change
5th Order Product
Note: As frequency range in this tool can be select just by specific blocks
it may not have accurate results, it calculate whole block frequency ranges.
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Frequency and BW change Date:
1st Nov-2023
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Frequency and BW change Date:
4th Nov-2023
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Frequency and BW change Date:
5th Nov-2023
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Frequency and BW change Date:
5th Nov-2023
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Thank You