Accurate modeling of open-ended coaxial sensor by non-uniform FDTD method

The open-ended coaxial sensor is modeled by a non-uniform FDTD method. Such sensors are used for complex permittivity measurements in the MHz-GHz frequency range. The accuracy of the measurements depend greatly on the accuracy of the reflection coefficient computation. The non-uniform grid makes it possible to use very fine discretization in the critical area where the open-end of the coax is attached to the sample. The method can be used to calculate the reflection coefficient for very thin samples.