AWT PIM-P, User Manual, Page: 86 / 110

10-2
PIM-P Analyzer User’s Manual
Copyright AWT-Global, LLC. All rights reserved.
PIM distortion is caused by non-linear mixing of two or more frequencies in passive
devices like cables and connectors. Ideal passive devices are considered linear. In reality
any linear component has a non-linear factor that can cause PIM distortion. For optimal
operation of RF systems, PIM has to be kept at a very low level that has virtually no
influence on the network operation. PIM signals are generally unwanted because they can
interfere with signals in a receive path.
10.1 What Causes PIM?
Passive intermodulation can be caused by a variety of factors. PIM distortion is often
the result of flaws in component design and manufacturing processes. PIM distortion may
also be caused by wear and tear on components due to mechanical constraints or
environmental conditions.
Manufacturing & Design 10.1.1

Use of ferromagnetic materials, such as nickel or steel, within the current path.
Especially at higher power levels, PIM can be generated due to hysteresis effect of
these materials and the non-linear voltage to current ratio.

Contaminations, like particles from machining operations or soldering splatters that
touch current carrying surfaces.

Separation of current carrying contact zones through irregular contact surfaces,
corrosion and insufficient contact pressure.

Dissimilar metals at contact areas.

Insufficient thickness of plated metal causing RF heating through the skin effect of
RF.

Bad solder joints.
Mechanical 10.1.2

Poor mechanical alignment of components

Too much or too little torque at connections

Contaminated connectors
Environment 10.1.3

Daily temperature variations, thermal loading by the sun and RF heating vary
junctions and can cause, often intermittent, PIM distortions.

Wind-induced vibrations vary junctions, and can weaken or break down joints.

Airborne dirt and moisture cause oxidation of materials and cause PIM distortion.
The antenna in the picture shows oxidation
within the power divider. Tests with vector analyzer
line sweep test would not reveal the problem;
however PIM testing detected the
issue
immediately