To address the problem of measuring the complex permittivity of mixtures of geological materials (homogeneous or mixtures) at RF frequencies (10MHz – 3 GHz), specific techniques are to be developed.
The main challenge of measuring this kind of mixtures is that each component could have a different state of aggregation (solid, liquid) and conglomeration (e.g. homogeneous, porous, granular). Traditional methods (i.e. capacitive fixture, waveguide, open-end coaxial probe) have been improved by exploiting dedicated procedures and processing.
FSS (passive and active) can be characterized both in terms of shielding effectiveness and backscattering, as a function of frequency as well as incident angles. Giving the different geometrical features of available samples, different free space or waveguide fixtures are available for testing.
A significant quantity of planar samples of RAM, RAS and RAP have been collected for characterization with: Standard Bistatic Measurement of Reflection coefficient (NRL ARCH), Pseudo far field behavior, Monostatic off normal incidence. The purpose is the verification of material properties and the population of IDS frameworks material data base. Characterization has been done by preparing canonical samples (plates, corners); performance degradation assessment has been repeated after simulated environment exposure (salt and UV). Further processing includes statistical characterization.
The Measurement Laboratory provides assessment of the properties of materials in terms of backscattering, shielding effectiveness and bulk properties (i.e. complex permittivity) for a wide range of materials and frequencies.Read more...