A New Handheld Sensor for Measuring Intrinsic Dielectric Properties at 100 to 1000 MHz

Traditional fixtures for UHF and VHF measurements of dielectric properties require specimens cut or machined with precision tolerances to avoid air gap errors. They also require significant handling and multi-step calibration procedures, complicating their use in non-laboratory applications. This paper introduces a new, non-traditional, measurement method for obtaining complex dielectric properties at UHF and VHF frequencies. It applies an open-ended stripline sensor in a handheld device that non-destructively measures reflection from a material surface. A novel computational electromagnetic (CEM) inversion methodology is applied to translate from reflection amplitude and phase into complex permittivity or sheet impedance. Because of this CEM inversion, the calibration is a simple one-step process. The CEM inversion method also enables characterization of multilayer structures as well as anisotropic materials. In addition to general principles for the device, example measurements as well as measurement comparisons to conventional dielectric measurement systems are presented.