Application of a SAR procedure for the determination of dielectric constants in free space

A synthetic aperture radar (SAR) procedure for the determination of dielectric constants in free space will be presented. For this purpose a material under test (MUT) is illuminated by a standard gain horn antenna. The antenna is moved automatically perpendicular to its main beam direction forming the synthetic aperture. The return loss of the SAR arrangement is obtained by superposing the individual return losses such that the contributions of the MUT to the scattered signals add up constructively whereas other sources of reflections cancel each other. The dielectric constant is determined by comparing the corresponding time domain response with that obtained by a 3D electromagnetic field simulator.