A slot line microwave dielectric permittivity sensor for measure and control of laminated materials

Measuring dielectric permittivity is a common technique to characterize malerials which, sometimes, allows also a non-destructive detection of interesting physical properties of objects and systems. A dielectric permittivity sensor far microwave frequency range is proposed, based on a slot line resonator loaded by the material under test which appears particularly suited for characterization of laminated type dielectric materials. The experimentally measured sensitivity resulted about 160 MHz/unit of ??r. Some results on the use of the sensor to detect air gaps inside dielectric materials are also reported.