Precise dielectric characterization of liquid crystal polymer films at microwave frequencies by new transverse slotted cavity

Liquid crystal polymer film provides an alternative to traditional polymer films for use as a substrate in microwave and millimeter wave flexible circuit construction. The liquid crystal polymer film has excellent mechanical properties and processability. However, due to the nature of the liquid crystal polymer molecules and the hot extrusion fabrication process, the liquid crystal polymer film will have strong molecular anisotropy. Therefore the dielectric properties will also have strong anisotropy. To precisely characterize the dielectric anisotropy accurately in microwave frequency range, a special slotted cavity for film materials is designed and fabricated. The derivation of the electromagnetic quantities for the new slotted cavity method resulted in accurate determination of dielectric permittivity and loss tangent of liquid crystal polymer films in anisotropic orientations.