Un metodo per la caratterizzazione di materiali dielettrici, mediante misure in campo vicino con antenne a patch

The paper describes a research activity developed in the frame of the CNR Special Project SP1a 'Nuove tecnologie per l'analisi non intrusiva dei manufatti', aimed to develop a non destructive material evaluation, based on microwave techniques. A narrow band planar antenna is used, whose resonant frequency depends on dielectric properties of the surrounding materials; the paper reports the study performed to assess the behaviour of a custom antenna in contact with materials having different dielectric properties. The paper reports a model describing analytically the antenna behaviour, the simulation results produced by a dedicated software that computes the electromagnetic fields produced by radiating devices and the experimental results obtained by examining samples with different thick and permittivity. The developed inspection method is able to satisfy research goals, consisting on the evaluation of local permittivities of a sample and on the comparison of different samples; the developed method can also give a good estimation of material permittivities in the 1 - 6 range.