Hello dear experts.
What is PIM in telecommunications?
PIM Definition
When transmitting 2 (or more) signals with different frequency into a passive component, due to bad connection or non-linear material in the component, it will generate a new frequency signal.
We call it Passive Intermodulation (PIM).
If the PIM is strong and falls into the receiving band, it will affect the performance of receiving channel.
Different Duplex Modes
In TDD the uplink and downlink occupy the same spectrum bandwidth. The receiving channel and transmitting channel are divided by time. The BS (Base Station) and UE (User Equipment) can cooperate with each other successfully when adopting the same configuration .
In FDD the receiving channel and transmitting channel are divided by spectrum bandwidth. The uplink and downlink are symmetrical, and will work at the same time.
Different RF Module Architectures
For all TDD systems, the receiving and transmitting channels work in different time at the same band. Therefore, a T/R RF switch is required to connect the receiving/transmitting channel of the system in different time slot.
When the downlink works, the RF switch is switched to the load . When the uplink works, the RF switch is switched to the receiver. Therefore, even if the PIM is generated in the downlink, it does not affect the uplink channel because the receiving channel is inactive.
So PIM is unnecessary for TDD antenna.
For FDD systems, the receiving and transmitting channels operate at different bands and a duplexer (equivalent to two filters) is required to separate the receiving and transmitting channels.
Since the uplink and downlink are working at the same time, if the PIM generated by the TX signal is strong and falls into the receiving band, the receiver’s noise will raise, the sensitivity will be deteriorated, and the uplink throughput will be lower.
So PIM is necessary for FDD antenna.
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Hi…PIM is a type of sign impedance, and it very well may be caused either by metal parts or by at least two bearers having the equivalent downlink way in a remote system, which is getting increasingly basic as remote systems become progressively unpredictable with various advancements and innovation ages at a solitary site. The signs consolidate to produce undesired obstruction, which impacts the LTE signal. Recieving wires, links, and filthy or free connectors can be wellsprings of PIM, thus can harmed RF hardware or metal items close or a good ways off from the phone site.
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Thanks @RFSpecialist , @AvrilPress
Could you explain procedure on passive intermodulation (PIM ) test for one cell?
We are experiencing this issue in one cell.
We have done a Sector swap and found an issue also swap. After we swap bandpass filter and issue remains.
Vendor confirmed that PIM issue is reason.
For PIM yo need to calculate 3rd and 5th order harmonic between two or three signals.
Usually, 2 DL signals can create an intermodulation product that may affect some UL.
