Reflection of Coherent Millimeter-Wave Wavelets on Dispersive Materials: A Study on Porcine Skin

Differences in the material reflection are required for any contrast in microwave- and millimeter-wave (mm-wave) imaging systems. Therefore, the dielectric properties, which determine the reflection of materials, need to be characterized. The characterization of skin and other biological tissue is, therefore, necessary, to apply imaging systems for instance in cancer diagnosis. In this paper, short, coherent mm-wave pulses (wavelets) are generated and their reflection on dispersive materials is studied. The reflections of wavelets on porcine skin and water are examined in time and frequency domain. A first-order Debye model is fitted to the reflection coefficient in frequency domain to quantify material dispersion. The frequency-dependent reflection on dispersive materials causes a distortion of the wavelets in the time domain. The startup behavior of the pulses is examined by simulation and measurements. The rise time of the pulses is identified as a feature in time domain for wavelets reflected on dispersive media. Together with other features characteristic for a pulse, for instance the wavelet amplitude, this enables identification of dispersive materials by reflectometry measurements, making it suitable for applications in mm-wave imaging systems.