Dielectric characterization of thin materials at 240 GHz

Characterization of different thin materials at millimeter-wave frequency, 240 GHz, is presented. This includes vegetation leaves as well as different types of fabrics. The complex permittivity retrieval algorithm is based on fitting the measured transmission coefficient at different incident angles to the corresponding analytical transmission coefficient of a simple dielectric slab. The extracted dielectric permittivity values for the fabrics are compared with the corresponding values measured at low microwave frequency (~1 GHz), using a standard material analyzer, where they are found to be nearly the same. For the leaf measurements, it is found that a simple dielectric mixing formula can be used to predict the value of dielectric permittivity.