IM variants extend selected AD and DiClad materials with a construction intended for antenna performance, including low PIM. They should be identified explicitly in drawings and comparisons rather than treated as interchangeable shorthand for the base grades.
Know which base material you are comparing
The library covers AD255C-IM, AD300D-IM and DiClad 880-IM. These options have different dielectric backgrounds, so first select a feasible antenna and feed geometry. Then evaluate the copper/interface construction and the available supporting PIM evidence.
Control the variables around a PIM result
A bench comparison needs the same tone plan, power reference, fixture quality and termination. Mount the samples consistently and inspect soldered transitions. Near the measurement floor, an apparent difference can come from the test arrangement; repeated measurements and a known reference are more informative than a single best reading. Material selection does not remove the need to control assembly cleanliness.
Turn the variant into a purchasing requirement
State the complete grade, dielectric thickness, foil and permitted substitutions in the fabrication package. Ask the fabricator to preserve identification through panel processing. For a long feed network, evaluate phase and insertion loss as well as PIM so the change supports the complete antenna requirement. Read PIM design considerations before setting a finished-board acceptance limit.
References in this family
Treat IM as a specified material construction and validate its benefit in your antenna's test conditions.