TEST AND MEASUREMENT
31
By Anritsu Company
www.anritsu.com
Field test solutions to locate PIM sources and
optimise performance are essential for maintaining
high-speed LTE networks
Operators promise that their LTE networks provide high-speed
and high-bandwidth – a claim field engineers and technicians
work diligently to keep. Ensuring that level of performance has
never been easy, and it continues to be a challenge due to
passive intermodulation (PIM), a growing issue in all mobile
networks. So field technicians and engineers need an efficient
PIM test solution to quickly correct PIM-based problems and
maintain network quality.
Simply defined, PIM is interference caused by new
frequencies generated by the transmit signals at a cell site,
which interact with non-linear elements in the RF path. If
these new frequencies fall in the uplink band, they can raise
the noise floor, causing high dropped call rates, access failures,
and slower data rates.
In the field, most PIM problems occur at metal-to-metal
connections and can be created by:
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Poor preparation of the coaxial cable where it interfaces
to the connector body
Loose or torn metal inside the connection caused by dull
cutting tools
Metal flakes left over by the cutting process
Improper assembly torque
All of these causes result in loose metal-to-metal contacts in
locations with very high RF current density. Considering it only
takes one metal flake – caused by mating or de-mating an
RF connector – to create PIM, it’s vital to clean connections
properly before mating. Even if RF connections are prepared
perfectly, they still require proper assembly torque to prevent
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