Hi, I have a question regarding the dielectric disk (bead form) in the precision adapter such as APC3.5 and APC 7 mm to N etc, not directly to PNA/ENA .... The disk is used to hold the central conductor in the right position, it is some kind of hard plast. What kind of matrials are usually used in these instrument class adapters/connnectors, such as those from Maury Microwave and Amphenol? What are their RF/mm wave characteristics?
There are many types of beads out there. Most are some form of low loss plastic or PTFE, some can be glass. Dielectric constants are usually low, maybe 2.5-4. This creates a discontinuity which is usually compensated for by changing the connector dimensions around the bead.
In a simulation, you can treat it as a lossless dielectric-filled coaxial structure (in between two air-filled coaxial structures).