Dielectric constant measurement of materials by a microwave technique: application to the characterization of vegetation leaves

A new microwave method proposed for modeling the plant leaves in the wave-guide is presented. In our model, we introduce a model based on the geometrical structure of vegetation leaves; water inside leaves is generally distributed between different tissues in not well-known proportions. To understand and predict its dielectric distribution behavior, it is necessary to involve its morphology; this leaf is parallel venation one with a midrib more developed than the minor veins. The physical phenomenon of diffraction occurs when a wave meets this type of structure. For this, we used the generalized equivalent circuit method. This dynamic method takes into account most of the involved physical phenomena. Calculating the permittivity of the material to be characterized from the measured reflection coefficient constitutes inverse problem. The complexity of the electromagnetic analysis does not allow to find an analytical relation between these two parameters. We have developed a computer code based on the genetic algorithm, to numerically solve the inverse problem. To validate this program, we performed measurements on standard materials of known permittivity. The method is verified with measurement of Teflon (PTFE), Flame Resistant 4, and Pure Acetone.