Micromachined 100GHz near-field measurement probe for high-resolution microwave skin-cancer diagnosis

This paper reports for the first time on a novel micromachined millimeter-wave near-field measurement probe for skin-cancer diagnosis, which is designed for high lateral resolution for resolving small skin cancer speckles as well as for vertically discriminating shallow tissue-layer anomalies. A tip size as small as 0.18 mm², which is 18times smaller than conventional measurement tips for the design frequency of 100 GHz, could be achieved by micromachining a silicon-core tapered dielectric-rod waveguide. This metallized dielectric probe is positioned centrally into a standard WR-10 waveguide by a micromachined holder which allows for easily exchanging the probes at high reproducibility. The dielectric-wedge transition between the waveguide and the probe is optimized for 100–105 GHz. Furthermore, this paper presents a unique concept of micromachined test samples with tailor-made permittivity ranging from 1.7 to 7.1, which enables emulation of the different water content of tissue anomalies. This test method results in highly reproducible test measurements for evaluating and comparing different prototype probe designs. The paper presents successful measurement results of fabricated probes and test samples. Different single test samples as well as sample stacks with emulated tissue anomalies could clearly be distinguished.