A Study On Inversion Algorithms For Measurement Of Complex Constants Of Media Of Electromagnetic Materials

In order to accurately obtain the electromagnetic parameters of the dielectric materials, somemeasurement techniques have been developed. By comparisons of the main techniques for themeasurement of electromagnetic parameters of materials, transmission/reflection method andreflection method are selected for the study of this thesis. Firstly, the basic principle of thetransmission/reflection method for measuring electromagnetic parameters is introduced. Then theinversion of the complex permittivity and permeability from the test data are given for both coaxialcable and rectangular waveguide. The suprious solution problems of the conventional NRWtransmission/reflection inversion algorithms is analysed, and a technique for real solution finding ispresented. The tests for the parameter measurements of polyfluortetraethylene verify the correctnessof the algorithm and usability of the algorithm in practice.Secondly, the basic principle of the reflection method for electromagnetic parametermeasurements is described. For the case of two-sample measurement in which the thickness of onesample is the twice of the other, only a cubic equation is needed to be solved for the simpleinversion for the parameters.For the versatility of the inversion algorithm, Newton iterative methodis employed to solve the roots of the transcendental equation which occurs in the general case. Thetest examples also verify the correctness and usability of the algorithm.Finally, effects of the test error of the S parameters are simulated and ananlyzed. It is foundthat the imaginary part of the inversed electromagnetic parameters is more sensitive to the test errorof the S paramenters. It can be concluded that the sensitivity can be decreased by properly changingthe thickness of the samples and the test frequency.