A measurement process to characterize natural and engineered low-loss uniaxial dielectric materials at microwave frequencies

We present a measurement method to characterize low-loss engineered materials and natural uniaxial dielectrics. Our approach employs a rectangular cavity coupled with tailored finite-element simulations to accurately determine the permittivity tensors; and loss tangents of material assemblies. Although similar approaches for natural crystals have been reported, this is the first time this method is adapted to engineered metamaterials. Loss-tangent measurements with an accuracy of 4-5 significant digits can be achieved by this simple and effective measurement approach. To demonstrate the method, we characterize a layered barium titanate-alumina stack and show that low-loss engineered crystals can be achieved via a proper choice of a bonding agent.