FEM Analysis Of Open-ended Coaxial-line Using For Dielectric Constant Measurement Of Microwave Biochemistry And Biological Tissue

Permittivity measurement has become increasingly important in microwave biochemistry and bio-electromagnetics in recent years. As a measurement probe, open-ended coaxial line has been used for permittivity measurement for many years. However, the traditional open-ended coaxial line is not suitable for the permittivity measurement of microwave biochemistry and biological tissues due to the erosion of them. A new structured open-ended coaxial line, which is suitable for measuring permittivity of erosive media, is presented. Applications of the probe in permittivity measurement of chemical reactant and biological layered tissues are discussed.The new structured and film coated open-ended coaxial line, whose open end is inclined, is simulated by using finite element method (FEM). Reflection coefficients of the same solution, which are measured by different incline probes, are calculated. And reflection coefficients changed as a function of permittivity of the solution at the different frequencies are calculated in order to get the relationship between reflection sensitivity and the frequency of electromagnetic wave. The solutions whose permittivities have been known, are measured by the new probe, and results are in good agreement with calculation results. In the meantime, the new structured coaxial probe is used to measure the dielectric properties of layered biological tissues. The reflection coefficients of the same model measured by different incline probes, are investigated, and relationship between reflection coefficient and conductivity of the layered tissue at different frequences is studied.The results of calculation prove: the new structured coaxial probe is superior tothe traditional coaxial probe in both sensitivity and penetrating depth when used to measure the dielectric properties of chemical reactants or layered biological tissues, and the relationship between the measurement sensitivity of this new structured probe and the frequency of electromagnetic wave are obtained, which provides the optimal frequency for the actual application.