Biaxial Permittivity Determination for Electrically Small Material Specimens of Complex Shape Using Shorted Rectangular Waveguide Measurements

A method for determining the complex anisotropic permittivity for electrically small material specimens of complex shape with biaxial dielectric anisotropy is described and representative measured results are presented. The method extracts the anisotropic tensor elements from specimen reflection measurements made with a shorted rectangular waveguide. A number of independent reflection measurements, using different specimen orientations in the waveguide equal to the number of unknown permittivity terms, are required. The specimens need not fill either dimension of the waveguide cross section and are permitted to be electrically short in the propagation direction. Measurements using WR1500 and WR1150 waveguide were made for a known isotropic low-loss dielectric specimen of complex shape. Additional measurements in WR1500 were made on two engineered anisotropic artificial dielectric specimens. Tensor permittivity elements were extracted from the measurements and were used to validate and demonstrate the accuracy and capability of the method by comparison with known values for the dielectric specimen or with explicit inclusion-binder simulation results for the engineered specimens.