A numerical study on the measurement region of an open-ended coaxial probe used for complex permittivity measurement

The measurement region of an open-ended coaxial probe with circular flange, which is used for measuring the complex permittivity, has been investigated by calculations and measurements. First, the detectable distance between the probe surface and metal plate in the saline solution is clarified by the experiments. Then, the electromagnetic field near the end of the probe, which affects the measurement strongly, has been analyzed by the finite-difference time-domain (FDTD) method. By identifying the measured and calculated results, the measurement region has been determined.