Characterization and Validation of the Slim-Form Open-Ended Coaxial Probe for the Dielectric Characterization of Biological Tissues at Millimeter-Wave Frequencies

This letter provides the calibration and optimization steps required for obtaining wideband millimeter-wave dielectric characteristics of human biological tissues using the commercially available slim-form open-ended coaxial probe. At the first stage, the reflection coefficients measured at the probe's calibration plane are transformed to the reflection coefficients of a desired aperture plane. Then, a rational optimization problem is solved to convert the aperture-plane reflection coefficients to dielectric permittivities. The measurement protocol is verified using three reference liquids and a test liquid representing dielectric characteristics of biological tissues.