Testing dielectric properties of tissue-equivalent liquid using open-ended coaxial line technique based on the transverse electromagnetic model

The experiments of the open-ended coaxial sensor used in the liquid dielectric properties testing based on the transverse electromagnetic (TEM) model are presented. In this approach, the input admittance at the coaxial opening end is approximated as a polynomial of the complex wave number in the liquid under test (LUT) that terminates the sensor, which gives advantageous to de-embedding the unknown complex permittivity by iteratively solving an algebraic equation. To avoid the inconveniences in using a short circuit reference load, the saline solution with known complex dielectric constants given by the empirical dispersion equations is used as an alternative in the calibration. The performance of measurements on dilute saline water and a 900MHz phantom head tissue-equivalent liquid (TEL) are verified by comparisons with the reference data.