A Reliable Attenuation Characterization of EMI Absorber Material at V-band Frequencies

Characterizing material at millimeter wave frequencies can be challenging. Test engineers have to make a proper choice between many different measurement configurations depending on the sample shape and nature of the interaction with the electromagnetic wave. Many existing experimental setups are optimised for dielectric materials and the determination of the complex permittivity but only few are handling strong losses in transmission which are typical for EMI materials. In this paper, the material characterization of EMI absorbers using a waveguide-based sample fixture around 60 GHz is discussed. The attenuation constant and the wave impedance are determined under consideration of the reflections at the material interfaces of the bulk material. Best practices for RF material characterization can be deduced for this particular case.