A planar-type probe with a coaxial aperture for nondestructive complex permittivity measurement of biological materials up to 30 GHz

In this paper, a planar probe structure is developed to evaluate the possibility of replacement of existing open-ended coaxial probes. The body of the probe is a planar transmission line that can propagate TEM mode and is completely shielded. For proper comparisons with open-ended coaxial probes, the proposed probe is designed to have a coaxial aperture on the top of the probe body using a via structure. The results of complex permittivity measurement show good agreement with those of open-ended coaxial-probes. Furthermore, it can reduce the fabrication cost and simplify the fabrication process by adopting the photolithography technique. Therefore the proposed planar type probe is a promising candidate for nondestructive dielectric measurement with respect to low cost and easier fabrication. In particular, it can be advantageous for in-vivo measurements due to its small size and disposability.