Pulse-Distortion Analysis for Millimeter-Wave Time-Domain Material Identification

Analyzing the frequency dependent dielectric properties can be used to identify and distinguish materials in biomedical instruments. In the millimeter-wave range, the dielectric properties of biological tissues are mainly determined by their water content. For instance, it has been shown, that cancer cells have a lower water content than healthy skin cells, resulting in a significant dielectric contrast between them. In this work, we analyze the pulse distortion observed in measurements of the millimeter-wave reflection of water and porcine skin. We propose to use the distortion caused by the frequency dependent reflection coefficient at the interface of a material as a feature for identification. Using a simplified model for the reflection coefficient of the material under test, we simulate the distortion caused by the frequency dispersion. In simulation as well as in measurement, we observe different startup transients depending on the dispersion properties of a material under test. The startup behavior can therefore be used as feature, to directly identify dispersive materials in the time domain.