The objective of this activity is to increase the accuracy of RF material characterisation by taking into account the scattering properties, which occur both in transmission and reflection, for rough or inhomogeneous/anisotropic materials. This will allow improving antenna analyses accuracy, using available modelling tools, by accounting for all possible effects extracted from these measurements.

 

 

Many different materials and composite materials are used in the field of antennas.Examples are dielectrics, frequency/polarisation selective surfaces, sandwich structures, Carbon Fiber Reinforced Plastics, ceramics, metal plates that can beseen in application ranging from low frequencies up to sub-mm waves. Anaccurate RF characterization of these materials is of vital importance for all future space missions.

 

A common way of describing these materials is in terms of (single) reflection,transmission and absorption. This is sufficient in case of homogeneous materials with perfectly flat interfaces. However, when the material is rough and/or inhomogeneous some of the incoming radiation will be scattered away in multiple directions. The magnitude and direction of this scattering is a function of the wavelength, refractive index of the material and the size of the inhomogeneity and will occur in both reflection and transmission. Therefore, in order to accurately derive the RF parameters (reflectivity, transmittivity, refractive index, ohmic losses, etc.) of the material, the way the reflectivity measurements is performed and processed shall be reconsidered. If this is not the case, then scattering will give rise to errors in the values of the reflection (R), transmission (T) and absorption.

 

Several Quasi-Optical (QO) benches have been developed in Europe, including at ESTEC, for RF material characterization. The outcome of this study shall be applicable to any QO bench in Europe and close the loop between simulations and measurements.

 

This activity will identify and implement the design adaptations of the RF characterisation test bench(es) and develop the required processing and data acquisition enabling the accurate RF characterisation. The measurement data shall be compatible with the state of the art electromagnetic simulators where the possibility of including the angular reflection and transmission properties of the materials is included. This will enable to accurately design the antenna and improve their performance predictions. The validation shall be performed on samples covering a large frequency range and type of structures.