Measurement of uniaxial anisotropy in Rogers RO3010 substrate material

A new technique using a dual mode “RA resonator” to measure uniaxial anisotropy in planar substrates is applied to Rogers RO3010 material. When this technique was previously applied to FR-4, an unexpected result (a horizontal dielectric constant less than the vertical dielectric constant) was obtained. It is hypothesized that the unexpected result is due to the fact that FR-4 is inhomogeneous. For example the glass fiber weave embedded in the FR-4 epoxy is not uniformly distributed. To test this hypothesis, similar measurements are performed on Rogers RO3010 material, which is strongly anisotropic, perfectly homogeneous, and is known from independent measurements to have a horizontal dielectric constant greater than the vertical. Several modifications to the original RA resonator that increase the frequency range over which useful measurements can be acquired are described and demonstrated.