High-power reflection coefficient measurement of biological material applicable to microwave hyperthermia

A measurement method for the high-power reflection coefficients of biological material applicable to microwave hyperthermia is presented. To extract the powerdependent complex permittivities, scalar S-parameter measurement setup consisting of a planar coaxial probe, impedance tuner, directional couplers, and power meters have been used. The tuner impedance was tuned until the reflected power reading was zeroed out, and subsequent de-embedding steps accounting for the non-idealities were followed to extract the reflection coefficient of the material under test at the coaxial aperture. To validate the proposed measurement method, the reflection coefficients of the distilled water were measured with various microwave powers at heated temperatures. The extracted complex permittivities showed good agreement with the reference data over broad temperature and frequency range. The method provides an effective way of in-situ monitoring during the hyperthermia and experimental data for thermalelectromagnetic analysis.