Research On Measurement Of Electromagnetic Characteristics Parameters For Microwave Dielectric Materials

Microwave dielectric materials have been widely used in aerospace, microwave communication, stealth technology, biomedical, electromagnetic compatibility and other fields; however, their electromagnetic characteristic parameters always need to be tested while in development, production and using. The article focuses on the research for the microwave dielectric material’s electromagnetic characteristic parameters testing systems and methods.(Elative complex permittivity, electromagnetic shielding effectiveness, absorbing performance). Main contents:(1) The electromagnetic parameter of the dielectric material can be measured by the opened coaxial probe method. First of all, building the theoretic modeling for opened coaxial method by using the Electromagnetic field method and the equivalent circuit theories methods, and the functional relationship between the complex reflection coefficient and complex permittivity could be established; therefore, we can find the reflection coefficient theoretical value of the sample material. After that, conducting simulations by using the electromagnetic simulation software HFSS on different opened coaxial probes according to the different dielectric materials loaded, and then obtain the corresponding reflection coefficient of the simulation value. Finally, measuring the reflection coefficient values of the dielectric materials by using the vector network analyzer and other instruments to get the actual results of reflection coefficient. After comparing the theoretical value, simulation value and the measured value, we found those three values matches very well, and it verifies the correctness of this modeling theory. At last, measured reflection coefficient values are substituted into the two theoretical models that mentioned above. Through the inversion calculation method, obtained the complex dielectric constants of dielectric material under each model, the error factors is also analyzed that were occurred in this experiments.(2) Measuring the shielding effectiveness of the shielding materials by applying the flange coaxial transmission line method. The measuring system of Shielding Effectiveness is constructed by connecting the test fixture and test instruments with PC through RS232. After the actual measurement to the sample materials, we found that the result value and the theoretical value are well matched which meets the practical measurement requirements. After measuring the sample materials’wave absorption efficiency by using the Waveguide test method, in addition of measuring standing-wave ratio, we obtained the reflectance of the measured materials which matches the theoretical value as well. It meets the requirements of the preliminary measurement.(3) Graphical user interface is designed by using MATLAB. A data processing software is also developed for this testing system. It can be used for dielectric constant inversion; analog computation of electromagnetic shielding and the theoretical value of Wave absorption efficiency; curve fitting, data graphic display, and graphics preservation function. It strengthens the data processing’s maneuverability and intuitiveness.