Challenges of RF Absorber Characterization: Comparison Between RCS- and NRL-Arch-Methods

Shielded anechoic chambers have become indispensable for radiated EMC and antenna measurements. The quality of such measurement facilities and thus of the measurements performed inside such environments depends sensitively on the reflectivity of the RF absorbers used. On the other side, the characterization of RF absorbers to ensure optimal measurement conditions is a challenging task. In this paper, the reflectivity of pyramidal absorbers is analyzed for frequencies between 1 GHz and 10 GHz using two different measurement methods: The NRL- Arch- and the RCS-method. The aim is to determine possible influences of the different approaches on the detectable reflectivity. Necessary post-processing steps and their applicability to the measured data are also discussed. It is shown that both methods can lead to nearly identical results, but even weak echoes of the surroundings may have major impact on the measurable reflectivity and thus lead to erroneous conclusions.